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<p>This file documents the <small>BASH</small> debugger <acronym>BASH</acronym>.
</p>
<p>This is the 4.0-0.4 Edition, 26 June 2009,
of <cite>Debugging with BASHDB: the <small>GNU</small> Source-Level Debugger</cite>
for BASH
</p>
<p>Copyright (C) 2002, 2003, 2004, 2006, 2007, 2008, 2009 Rocky Bernstein for the Free Software Foundation.
</p>
<p>Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation; with no
Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
</p>
<a name="Top"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Top" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Function-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Debugging-with-the-BASH-debugger"></a>
<h1 class="settitle">Debugging with the <acronym>BASH</acronym> debugger</h1>
<p>This file describes the <acronym>BASH</acronym> debugger, the <small>BASH</small> symbolic debugger.
</p>
<p>This is the 4.0-0.4 Edition, 26 June 2009, for BASH.
</p>
<p>Copyright (C) 2002, 2003, 2004, 2006, 2007, 2008, 2009 Rocky Bernstein
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top"><a href="#Summary">1. Summary of the BASH Debugger</a></td><td> </td><td align="left" valign="top"> Overview of Debugger with a sample session
</td></tr>
<tr><td align="left" valign="top"><a href="#Invocation">2. Getting in and out</a></td><td> </td><td align="left" valign="top"></td></tr>
<tr><td align="left" valign="top"><a href="#Running">3. Script Setup inside the BASH Debugger</a></td><td> </td><td align="left" valign="top"> Script setup inside the BASH debugger
</td></tr>
<tr><td align="left" valign="top"><a href="#Debugger-Command-Reference">4. BASH Debugger Command Reference</a></td><td> </td><td align="left" valign="top"> BASH debugger command reference
</td></tr>
<tr><td align="left" valign="top"><a href="#Front-Ends">5. Using the <acronym>BASH</acronym> debugger from a front-end user interface</a></td><td> </td><td align="left" valign="top"> Using the Debugger from a front-end user interface
</td></tr>
<tr><td align="left" valign="top"><a href="#BASH-Debugger-Bugs">6. Reporting Bugs</a></td><td> </td><td align="left" valign="top"> Reporting bugs
</td></tr>
<tr><td align="left" valign="top"><a href="#History-and-Acknowledgments">7. History and Acknowledgments</a></td><td> </td><td align="left" valign="top"></td></tr>
<tr><th colspan="3" align="left" valign="top"><pre class="menu-comment">
Appendices
</pre></th></tr><tr><td align="left" valign="top"><a href="#Copying">A. GNU GENERAL PUBLIC LICENSE</a></td><td> </td><td align="left" valign="top"> GNU General Public License says
how you can copy and share bashdb
</td></tr>
<tr><td align="left" valign="top"><a href="#GNU-Free-Documentation-License">B. GNU Free Documentation License</a></td><td> </td><td align="left" valign="top"> The license for this documentation
</td></tr>
<tr><th colspan="3" align="left" valign="top"><pre class="menu-comment">
Indexes (nodes containing large menus)
</pre></th></tr><tr><td align="left" valign="top"><a href="#Function-Index">Function Index</a></td><td> </td><td align="left" valign="top"> An item for each function name.
</td></tr>
<tr><td align="left" valign="top"><a href="#Command-Index">Command Index</a></td><td> </td><td align="left" valign="top"> An item for each command name.
</td></tr>
<tr><td align="left" valign="top"><a href="#Variable-Index">Variable Index</a></td><td> </td><td align="left" valign="top"> An item for each documented variable.
</td></tr>
<tr><td align="left" valign="top"><a href="#General-Index">General Index</a></td><td> </td><td align="left" valign="top"> An item for each concept.
</td></tr>
</table>
<hr size="1">
<a name="Summary"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Top" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#Sample-Session" title="Next section in reading order"> > </a>]</td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Top" title="Beginning of this chapter or previous chapter"> << </a>]</td>
<td valign="middle" align="left">[<a href="#Top" title="Up section"> Up </a>]</td>
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<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Top" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Function-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Summary-of-the-BASH-Debugger"></a>
<h1 class="chapter">1. Summary of the BASH Debugger</h1>
<p>The purpose of a debugger such as the <acronym>BASH</acronym> debugger is to allow you to see what is
going on “inside” a bash script while it executes.
</p>
<p>the <acronym>BASH</acronym> debugger can do four main kinds of things (plus other things in support of
these) to help you catch bugs in the act:
</p>
<ul>
<li>
Start your script, specifying anything that might affect its behavior.
</li><li>
Make your script stop on specified conditions.
</li><li>
Examine what has happened, when your script has stopped.
</li><li>
Change things in your script, so you can experiment with correcting the
effects of one bug and go on to learn about another.
</li></ul>
<p>Although you can use the <acronym>BASH</acronym> debugger to debug scripts
written in <acronym>BASH</acronym>, it can also be used just as a front-end
for learning more about programming in <acronym>BASH</acronym>. As an
additional aid, the debugger can be used within the context of an
existing script with its functions and variables that have already
been initialized; fragments of the existing can be experimented with
by entering them inside the debugger.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top"><a href="#Sample-Session">1.1 A Sample BASH Debugger Session</a></td><td> </td><td align="left" valign="top"> A Sample BASH Debugger session
</td></tr>
<tr><td align="left" valign="top"><a href="#Interactive-Line-Tracing-Session">1.2 Interactive Line Tracing Session</a></td><td> </td><td align="left" valign="top"></td></tr>
</table>
<hr size="6">
<a name="Sample-Session"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Summary" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#Interactive-Line-Tracing-Session" title="Next section in reading order"> > </a>]</td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Summary" title="Beginning of this chapter or previous chapter"> << </a>]</td>
<td valign="middle" align="left">[<a href="#Summary" title="Up section"> Up </a>]</td>
<td valign="middle" align="left">[<a href="#Invocation" title="Next chapter"> >> </a>]</td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Top" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Function-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="A-Sample-BASH-Debugger-Session"></a>
<h2 class="section">1.1 A Sample BASH Debugger Session</h2>
<p>You can use this manual at your leisure to read all about the <acronym>BASH</acronym> debugger.
However, a handful of commands are enough to get started using the
debugger. This chapter illustrates those commands.
</p>
<p>Below we will debug a script that contains a function to compute the
factorial of a number: fact(0) is 1 and fact(n) is n*fact(n-1).
</p>
<table><tr><td> </td><td><pre class="smallexample">$ <b>bashdb -L . /tmp/fact.sh</b>
Bourne-Again Shell Debugger, release bash-4.0-0.4
Copyright 2002, 2003, 2004, 2006, 2007, 2008, 2009 Rocky Bernstein
This is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
(/tmp/fact.sh:9):
9: echo fact 0 is: `fact 0`
bashdb<0> <b>-</b>
1: #!/usr/local/bin/bash
2: fact() {
3: ((n==0)) && echo 1 && return
4: ((nm1=n-1))
5: ((result=n*`fact $nm1`))
6: echo $result
7: }
8:
9:==> echo fact 0 is: `fact 0`
bashdb<1> <b>list</b>
10: echo fact 3 is: $(fact 3)
</pre></td></tr></table>
<p>The command invocation uses the option “-L .” Here we assume that
the <code>bashdb</code> script and the debugger files are in the same
location. If you are running from the source code, this will be the
case. However if bashdb has been installed this probably won’t be true
and here you probably don’t need to use “-L .” Instead you would
type simply <code>bashdb /tmp/fact.sh</code>.
</p>
<p>Position information consists of a filename and line number,
e.g. <code>(/tmp/fact.sh:9)</code> and is given parenthesis. This position
format is similar to that used by the Perl debugger and is also in the
same format used by my GNU make debugger
(<a href="http://bashdb.sourceforge.net/remake">http://bashdb.sourceforge.net/remake</a>) the Extended Python
Debugger <a href="http://remake.sourceforge.net/pydb">http://remake.sourceforge.net/pydb</a>, and one for Ruby
(<a href="http://bashdb.sorceforge.net/ruby-debug.html">http://bashdb.sorceforge.net/ruby-debug.html</a>). GNU Emacs and
DDD can parse this and in fact the same regular expression is used on
the 3 debuggers.
</p>
<p>The first debugger command we gave <kbd>-</kbd>, we listed a window of
lines <em>before</em> where we were executing. Because the window, 10
lines, is larger than the number of lines to the top of the file we
printed only 9 lines here. The next command, <code>list</code>, starts from
the current line and again wants to print 10 lines but because there
are only one remaining line, that is what is printed.
</p>
<table><tr><td> </td><td><table class="cartouche" border="1"><tr><td>
<pre class="smallexample">bashdb<2> <b>step</b>
(/tmp/fact.sh:9):
fact 0
9: echo fact 0 is: `fact 0`
bashdb<(3)> <b><RET></b>
2: fact() {
bashdb<(4)> <b><RET></b>
3: ((n==0)) && echo 1 && return
bashdb<(5)> <b>print $n</b>
bashdb<(6)>
</pre></td></tr></table>
</td></tr></table>
<p>Ooops... The variable <kbd>n</kbd> isn’t initialized.<a name="DOCF1" href="#FOOT1">(1)</a>
</p>
<p>The first <kbd>step</kbd> command steps the script one instruction. It may
seem odd that the line printed is exactly the same one as before. What
has happened though is that we’ve “stepped” into the subshell needed
to run <kbd>`fact 0`</kbd>; we haven’t however started running anything
inside that subshell yet though.
</p>
<p>To indicate that which piece of the multi-part line <code>echo fact 0
is: `fact 0`</code> we show that part all by itself <kbd>fact 0</kbd>. If nothing
is shown then it means we are running the beginning statement or in
this case the outermost statement.
</p>
<p>To indicate that we are now nested in a subshell, notice that the
command number, starting with 3, or the third command entered, now
appears in parenthesis. Each subshell nesting adds a set of
parenthesis.
</p>
<p>The first <kbd>step</kbd> command steps the script one instruction; it
didn’t advance the line number, 9, at all. That is because we were
stopping before the command substitution or backtick is to take
place. The second command we entered was just hitting the return key;
bashdb remembers that you entered <code>step</code> previously, so it runs
the step rather than <kbd>next</kbd>, the other alternative when you hit
<RET>. Step one more instruction and we are just before running
the first statement of the function.
</p>
<p>Next, we print the value of the variable <kbd>n</kbd>. Notice we need to add
a preceding dollar simple to get the substitution or value of n. As we
will see later, if the <kbd>pe</kbd> command were used this would not be
necessary.
</p>
<p>We now modify the file to add an assignment to local variable <kbd>n</kbd> and
restart.
</p>
<table><tr><td> </td><td><table class="cartouche" border="1"><tr><td>
<pre class="smallexample">bashdb<6> <b>restart</b>
Restarting with: /usr/local/bin/bashdb -L . fact.sh
(/tmp/fact.sh:10):
10: echo fact 0 is: `fact 0`
bashdb<0> <b>list 1</b>
1: #!/usr/local/bin/bash
2: fact() {
3: local -i n=${1:0}
4: ((n==0)) && echo 1 && return
5: ((nm1=n-1))
6: ((result=n*`fact $nm1`))
7: echo $result
8: }
9:
10:==> echo fact 0 is: `fact 0`
bashdb<1> <b>s 3</b>
(/tmp/fact.sh:3):
3: local -i n=${1:0}
bashdb<(2)> <b>step</b>
(/tmp/fact.sh:4):
4: ((n==0)) && echo 1 && return
bashdb<(3)> <b>print $n</b>
print $n
0
</pre></td></tr></table>
</td></tr></table>
<p>This time we use the <code>list</code> debugger command to list the lines in
the file. From before we know it takes three <code>step</code> commands
before we get into the fact() function, so we add a count onto the
<code>step</code> command. Notice we abbreviate <code>step</code> with <code>s</code>;
we could have done likewise and abbreviated <code>list</code> with <code>l</code>.
</p>
<table><tr><td> </td><td><table class="cartouche" border="1"><tr><td>
<pre class="smallexample">bashdb<(4)> <b><RET></b>
(/tmp/fact.sh:4):
4: ((n==0)) && echo 1 && return
echo 1
bashdb<(5)> <b><RET></b>
(/tmp/fact.sh:4):
4: ((n==0)) && echo 1 && return
return
</pre></td></tr></table>
</td></tr></table>
<p>Again we just use <RET> to repeat the last <code>step</code>
commands. And again the fact that we are staying on the same line 4
means that the next condition in the line is about to be
executed. Notice that we see the command (<code>echo 1</code> or
<code>return</code>) listed when we stay on the same line which has multiple
stopping points in it. Given the information above, we know that the
value echo’ed on return will be 1.
</p>
<table><tr><td> </td><td><table class="cartouche" border="1"><tr><td>
<pre class="smallexample">bashdb<(6)> <b><RET></b>
fact 0 is: 1
(/tmp/fact.sh:12):
12: echo fact 3 is: $(fact 3)
bashdb<(7)> <b>break 5</b>
Breakpoint 1 set in file fact.sh, line 5.
bashdb<(8)> <b>continue</b>
</pre></td></tr></table>
</td></tr></table>
<p>We saw that we could step with a count into the function
fact(). However above took another approach: we set a stopping point or
“breakpoint” at line 5 to get us a little ways into the fact()
subroutine. Just before line 5 is to executed, we will get back into
the debugger. The <code>continue</code> command just resumes execution until
the next stopping point which has been set up in some way.
</p>
<table><tr><td> </td><td><table class="cartouche" border="1"><tr><td>
<pre class="smallexample">(/tmp/fact.sh:5):
5: ((nm1=n-1))
Breakpoint 1 hit(1 times).
bashdb<(8)> <b>x n-1</b>
2
bashdb<(9)> <b>s</b>
(/tmp/fact.sh:5):
6: ((result=n*`fact $nm1`))
bashdb<(10)> <b>c</b>
fact.sh: line 6: ((: result=n*: syntax error: operand expected (error token is "*")
bashdb<(7)> <b>R</b>
Restarting with: bash --debugger fact.sh
11: echo fact 0 is: `fact 0`
bashdb<0> <b>l fact</b>
2: fact ()
3: {
4: local -i n=${1:0};
5: (( "n==0" )) && echo 1 && return;
6: (( nm1=n-1 ));
7: ((fact_nm1=`fact $nm1`))
8: (( "result=n*fact_nm1" ));
9: echo $result
10: }
</pre></td></tr></table>
</td></tr></table>
<p>In addition to listing by line numbers, we can also list giving a
function name. Below, instead of setting a breakpoint at line 5 and
running “<code>continue</code>” as we did above, we try something slightly
shorter and slightly different. We give the line number on the
“continue” statement. This is a little different in that a one-time
break is made on line 5. Once that statement is reached the breakpoint
is removed.
</p>
<table><tr><td> </td><td><table class="cartouche" border="1"><tr><td>
<pre class="smallexample">bashdb<1> <b>continue 5</b>
One-time breakpoint 1 set in file fact.sh, line 5.
fact 0 is: 1
(/tmp/fact.sh:5):
5: ((nm1=n-1))
bashdb<(2)> <b>s</b>
6: ((fact_nm1=`fact $nm1`))
bashdb<(3)> <b>s</b>
2: fact() {
bashdb<(4)> <b>T</b>
->0 in file `fact.sh' at line 2
##1 fact("3") called from file `fact.sh' at line 12
##2 source("fact.sh") called from file `/usr/local/bin/bashdb' at line 154
##3 main("fact.sh") called from file `/usr/local/bin/bashdb' at line 0
bashdb<(5)> <b>c</b>
fact 3 is: 6
Debugged program terminated normally. Use q to quit or R to restart.
</pre></td></tr></table>
</td></tr></table>
<p>When we stop at line 5 above, we have already run fact(0) and output
the correct results. The output from the program “fact 0 is: 1” is
intermixed with the debugger output. The <code>T</code> command above
requests call stack output and this confirms that we are not in the
fact(0) call but in the fact(3) call. There are 4 lines listed in the
stack trace even though there is just one call from the main
program. The top line of the trace doesn’t really represent a call,
it’s just where we currently are in the program. That last line is an
artifact of invoking bash from the bashdb script rather than running
<code>bash --debugger</code>.
</p>
<p>The last message in the output above ‘<samp>Debugged program exited
normally.</samp>’ is from the <acronym>BASH</acronym> debugger; it indicates script has finished
executing. We can end our bashdb session with the bashdb
<code>quit</code> command.
</p>
<p>Above we did our debugging session on the command line. If you are a
GNU Emacs user, you can do your debugging inside that. Also there is
a(nother) GUI interface called DDD that supports the <acronym>BASH</acronym> debugger.
</p>
<hr size="6">
<a name="Interactive-Line-Tracing-Session"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Sample-Session" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#Invocation" title="Next section in reading order"> > </a>]</td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Summary" title="Beginning of this chapter or previous chapter"> << </a>]</td>
<td valign="middle" align="left">[<a href="#Summary" title="Up section"> Up </a>]</td>
<td valign="middle" align="left">[<a href="#Invocation" title="Next chapter"> >> </a>]</td>
<td valign="middle" align="left"> </td>
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Interactive-Line-Tracing-Session-1"></a>
<h2 class="section">1.2 Interactive Line Tracing Session</h2>
<p><a name="PS4"></a>
<a name="index-_0024PS4"></a>
</p>
<p>One of the things I had found disappointing about the
default <code>set -x</code> tracing behavior is that no position information
is given in the trace output, in particular the line number and the file
name. However with the introduction in Bash 3.0 of the introspection
variables, aslo needed to support the debugger, one can set
<code>$PS4</code> to rectify this. (I became of this in a defunct blog
<a href="http://raz.cx/blog/2005/08/handy-bash-debugging-trick.html">http://raz.cx/blog/2005/08/handy-bash-debugging-trick.html</a>.)
</p>
<p>Here’s what I use:
</p><table><tr><td> </td><td><pre class="smallexample"> PS4='(${BASH_SOURCE}:${LINENO}): ${FUNCNAME[0]} - [${SHLVL},${BASH_SUBSHELL}, $?]
'
</pre></td></tr></table>
<p>Note that the string is in single quotes, not double quotes and there
is a newline in the string. By using single quotes, variables which
have a dollar in front of them in the string are expanded in the
current environment of the line that is about to be run rather than at
the time the variable <code>PS4</code> is set.
</p>
<p>You might want to add this in your shell’s start-up script, e.g.,
<code>.bashrc</code>, or <code>.profile</code>.
</p>
<p>There is also facility inside the bash debugger showing position
information when tracing a script. Here’s a simple session.
</p>
<table><tr><td> </td><td><pre class="smallexample"><b>/usr/local/bin/bashdb /tmp/fact.sh</b>
Bourne-Again Shell Debugger, release bash-4.0-0.4
Copyright 2002, 2003, 2004, 2006, 2007, 2008 Rocky Bernstein
This is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
(/tmp/fact.sh:11):
11: echo fact 0 is: `fact 0`
bashdb<0> <b>set linetrace on</b>
bashdb<1> <b>cont</b>
(/tmp/fact.sh:11):
level 1, subshell 1, depth 0: echo fact 0 is: `fact 0`
fact 0
(/tmp/fact.sh:2):
level 1, subshell 1, depth 1: fact() {
(/tmp/fact.sh:3):
level 1, subshell 1, depth 1: local -i n=${1:0}
(/tmp/fact.sh:4):
level 1, subshell 1, depth 1: ((n==0)) && echo 1 && return
(/tmp/fact.sh:4):
level 1, subshell 1, depth 1: ((n==0)) && echo 1 && return
echo 1
(/tmp/fact.sh:4):
level 1, subshell 1, depth 1: ((n==0)) && echo 1 && return
return
fact 0 is: 1
(/tmp/fact.sh:13):
level 1, subshell 0, depth 0: echo fact 3 is: $(fact 3)
(/tmp/fact.sh:13):
level 1, subshell 1, depth 0: echo fact 3 is: $(fact 3)
fact 3
(/tmp/fact.sh:2):
level 1, subshell 1, depth 1: fact() {
(/tmp/fact.sh:3):
level 1, subshell 1, depth 1: local -i n=${1:0}
(/tmp/fact.sh:4):
level 1, subshell 1, depth 1: ((n==0)) && echo 1 && return
(/tmp/fact.sh:5):
level 1, subshell 1, depth 1: ((nm1=n-1))
(/tmp/fact.sh:6):
level 1, subshell 1, depth 1: ((fact_nm1=`fact $nm1`))
(/tmp/fact.sh:6):
level 1, subshell 2, depth 1: ((fact_nm1=`fact $nm1`))
fact $nm1
(/tmp/fact.sh:2):
level 1, subshell 2, depth 2: fact() {
...
level 1, subshell 4, depth 4: fact() {
(/tmp/fact.sh:3):
level 1, subshell 4, depth 4: local -i n=${1:}
(/tmp/fact.sh:4):
level 1, subshell 4, depth 4: ((n==0)) && echo 1 && return
(/tmp/fact.sh:4):
level 1, subshell 4, depth 4: ((n==0)) && echo 1 && return
echo 1
(/tmp/fact.sh:4):
level 1, subshell 4, depth 4: ((n==0)) && echo 1 && return
return
(/tmp/fact.sh:7):
level 1, subshell 3, depth 3: ((result=n*fact_nm1))
(/tmp/fact.sh:8):
level 1, subshell 3, depth 3: echo $result
(/tmp/fact.sh:7):
level 1, subshell 2, depth 2: ((result=n*fact_nm1))
(/tmp/fact.sh:8):
level 1, subshell 2, depth 2: echo $result
(/tmp/fact.sh:7):
level 1, subshell 1, depth 1: ((result=n*fact_nm1))
(/tmp/fact.sh:8):
level 1, subshell 1, depth 1: echo $result
fact 3 is: 6
(/usr/local/bin/bashdb:260):
level 1, subshell 0, depth -1:
Debugged program terminated normally. Use q to quit or R to restart.
bashdb<2>
</pre></td></tr></table>
<p>An explanation of the output. The <em>level</em> is how many invocations
of <acronym>BASH</acronym> are in effect before the statement shown is
executed. The <em>subshell</em> is how many subshells you are nested
in. Subshells are used by command substitution—<code>`..'</code> and
<code>$(...)</code>—as well as arithmetic expressions <code>((...))</code>. The
<em>depth</em> is the function depth or how many calls you are nested
in. A “source” command also increases this depth.
</p>
<p>Notice also that in contrast to <code>set -x</code> tracing, the line shown
is exactly as you entered it in the source. So if you indented
statements in a meaningful way, it will help you understand the
statement nesting level. But as before, if a line contains multiple
statements, you are <em>not</em> executing the first statement in the
line and <code>set showcommand</code> is not turned off (by default it is
on), that statement is shown in addition below the multi-statement
line. Such an example can be seen right at the beginning where
<code>fact 0</code> is shown.
</p>
<p>If what you want to do is trace the <em>entire</em> script as was done
above (and not stop in the debugger when the script is over), you can
get the same effect by using the <code>-X</code> or <code>--trace</code> option on
the <code>bashdb</code> command:
</p>
<table><tr><td> </td><td><pre class="smallexample"><b>/usr/local/bin/bashdb -X /tmp/fact.sh</b>
Bourne-Again Shell Debugger, release bash-4.0-0.4
Copyright 2002, 2003, 2004, 2006, 2007, 2008, 2009 Rocky Bernstein
This is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
(/usr/local/bin/bashdb:272):
level 1, subshell 0, depth -1: . $_source_file
(/tmp/fact.sh:11):
level 1, subshell 0, depth 0: echo fact 0 is: `fact 0`
(/tmp/fact.sh:11):
level 1, subshell 1, depth 0: echo fact 0 is: `fact 0`
fact 0
(/tmp/fact.sh:2):
level 1, subshell 1, depth 1: fact() {
(/tmp/fact.sh:3):
level 1, subshell 1, depth 1: local -i n=${1:0}
...
level 1, subshell 2, depth 2: echo $result
(/tmp/fact.sh:7):
level 1, subshell 1, depth 1: ((result=n*fact_nm1))
(/tmp/fact.sh:8):
level 1, subshell 1, depth 1: echo $result
fact 3 is: 6
(/usr/local/bin/bashdb:285):
level 1, subshell 0, depth -1:
</pre></td></tr></table>
<p>If you issue a break (e.g. send a <code>SIGINT</code> signal) while the
program is running you will go into the debugger (assuming your
program doesn’t trap <code>SIGINT</code>).
</p>
<hr size="6">
<a name="Invocation"></a>
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<a name="Getting-in-and-out"></a>
<h1 class="chapter">2. Getting in and out</h1>
<p>This chapter discusses how to start the <acronym>BASH</acronym> debugger, and how to get out of it.
The essentials are:
</p><ul>
<li>
type ‘<samp>bash --debugger <em>script-name</em></samp>’ or ‘<samp>bashdb
<em>script-name</em></samp>’ to start the <acronym>BASH</acronym> debugger. Or...
</li><li>
type ‘<samp>bashdb -c <em>command string</em></samp>’ to give a string to run
under the debugger. Or ..
</li><li>
modify your program to enter the debugger at a particular point:
<code>source ../bashdb-trace</code> and <code>_Dbg_debugger</code>.
</li><li>
type <kbd>quit</kbd> or <kbd>C-d</kbd> inside the debugger to exit.
</li></ul>
<p>There are also two front-ends available as well. One can also
enter the debugger inside emacs via the command <code>M-x bashdb</code>
after loading Emacs’ Grand Unified Debugger, <code>gud</code>. See
<a href="#Emacs">Using the BASH debugger from <small>GNU</small> Emacs</a>. And there is
support in a <acronym>DDD</acronym> for bash.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top"><a href="#Starting-the-BASH-debugger">2.1 Starting the BASH debugger</a></td><td> </td><td align="left" valign="top"> How to enter the BASH debugger
</td></tr>
<tr><td align="left" valign="top"><a href="#Quitting-the-BASH-debugger">2.2 Quitting the BASH debugger</a></td><td> </td><td align="left" valign="top"> How to leave the BASH debugger
</td></tr>
<tr><td align="left" valign="top"><a href="#Calling-from-Program">2.3 Calling the BASH debugger from inside your program</a></td><td> </td><td align="left" valign="top"> Calling the debugger from inside your program
</td></tr>
</table>
<hr size="6">
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<a name="Starting-the-BASH-debugger-1"></a>
<h2 class="section">2.1 Starting the BASH debugger</h2>
<p><em>Note: it is important to use a debugger-enabled bash. You will
get an error message if the debugger is run under a version of BASH
that does not have debugging support.</em>
</p>
<p>As mentioned above, one can enter the <acronym>BASH</acronym> debugger via Emacs or
DDD. However you don’t have to use either of these. And these still
need a way on their own to get things started.
</p>
<p>There are in fact two <em>other</em> ways to start the <acronym>BASH</acronym> debugger. The
first way is to pass the ‘<samp>--debugger</samp>’ option to bash with the
name of your script the scripts arguments following that, or with a
command string (<code>-c</code>).
</p>
<table><tr><td> </td><td><pre class="example">bash --debugger <var>script</var> <var>script-arguments...</var>
bash --debugger -c <var>command-string</var>...
</pre></td></tr></table>
<p>This calls a debugger initialization script. It works much like a
<acronym>BASH</acronym> login profile which may set variables and define
functions. But this shell profile is customized for debugging and as
such arranges for itself to get called before each statement is
executed. Although there are some problems at present in I/O
redirection that the method described next doesn’t have, it is
expected that over time more features will be enabled in bash when the
‘<samp>--debugger</samp>’ option is in effect. By default, both debugging in
Emacs via GUD (<a href="#Emacs">Using the BASH debugger under Emacs</a>) and
debugging via <acronym>DDD</acronym> work via this method.
</p>
<p>The form ‘<samp>bash --debugger -c ...</samp>’ can be used to get into the
debugger without having to give a script name to debug. Sometimes you
may want to do this just to see how the debugger works: try some
debugger commands or maybe get online help. If you run <code>ddd
--bash</code> without giving a script name, it in fact uses this form.
</p>
<p>In order for the ‘<samp>--debugger</samp>’ option to work however, you must
have the debugger scripts installed in a place where the <acronym>BASH</acronym> debugger can find
them. For this reason, in developing the <acronym>BASH</acronym> debugger, I use a second
method more often; it doesn’t require the bash debugger to be
installed. This method uses another script called <code>bashdb</code> which
allows for giving its own options, the final option is signaled by
adding <code>--</code>). After this, the name of the script to debugged and
any the arguments to pass to that script are given. Using this method,
one would start the debugger like this:
</p>
<table><tr><td> </td><td><pre class="example">bash <var>path-to-bashdb</var>/bashdb <var>bashdb-options</var> -- <var>script</var> <var>script-arguments...</var>
</pre></td></tr></table>
<p>If you don’t need to pass dash options to your program which might get
confused with the debugger options, then you don’t need to add the
<code>--</code>.<a name="DOCF2" href="#FOOT2">(2)</a>
</p>
<p>As with the first method, <code>bash</code> should be a debugger-enabled
bash. If <code>bashdb</code> has the path to bash in it at the top (e.g. via
<code>#!</code>), and <code>bashdb</code> can be found in your program-search
path, then this might be equivalent to the above:
</p>
<table><tr><td> </td><td><pre class="example">bashdb <var>bashdb-options</var> -- <var>script</var> <var>script-arguments...</var>
</pre></td></tr></table>
<p>There are two or three disadvantages however of running a debugger
this way. First <code>$0</code> will have the value <code>bashdb</code> rather
than the script you are trying to run. For some scripts this may
change the behavior of the debugged script. Second a traceback will
contain additional lines showing the “source”-ing of the debugged
script from <code>bashdb</code>. And third, although this way works better
than the first method, over time this way may come into disuse.
</p>
<p>An option that you’ll probably need to use if bashdb isn’t installed
but run out of the source code directory is ‘<samp>-L</samp>’ which specifies
the directory that contains the debugger script files.
</p>
<p>You can further control how bashdb starts up by using command-line
options. bashdb itself can remind you of the options available.
</p>
<p>Type
</p>
<table><tr><td> </td><td><pre class="example">bashdb -h
</pre></td></tr></table>
<p>to display all available options and briefly describe their use.
</p>
<p>When the bash debugger is invoked either by the <code>bashdb</code>
front-end script or <code>bash --debugging</code>, the first argument that
does not have an associated option flag for <code>bashdb</code> or
<code>bash</code> (as the case may be) is used as the name a the script file
to be debugged, and any following options get passed the debugged
script.
</p>
<p>Options for the <code>bashdb</code> front-end are shown in the
following list.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top"><a href="#Options-for-the-bashdb-script">2.1.1 Command-line options for <code>bashdb</code> script</a></td><td> </td><td align="left" valign="top"> Options you can pass in starting bashdb
</td></tr>
</table>
<hr size="6">
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</tr></table>
<a name="Command_002dline-options-for-bashdb-script"></a>
<h3 class="subsection">2.1.1 Command-line options for <code>bashdb</code> script</h3>
<p>You can run the <acronym>BASH</acronym> debugger in various alternative modes—for example, in batch
mode or quiet mode.
</p>
<dl compact="compact">
<dt> <code>-h | --help</code></dt>
<dd><a name="index-_002dh"></a>
<a name="index-_002d_002dhelp"></a>
<p>This option causes the <acronym>BASH</acronym> debugger to print some basic help and exit.
</p>
</dd>
<dt> <code>-V | --version</code></dt>
<dd><a name="index-_002dV"></a>
<p>This option causes the <acronym>BASH</acronym> debugger to print its version number,
no-warranty blurb, and exit.
</p>
</dd>
<dt> <code>-A | --annodate <var>level</var></code></dt>
<dd><a name="index-_002dA"></a>
<a name="index-_002d_002dannotate"></a>
<p>Add additional output which allows front-ends to track what’s going on
without having to poll for such vital information. The default
annotation level is 0 (none). If you are running inside GNU Emacs
using the Emacs code from this package, an annotation level 3 when set
will allow for automatic tracking of frames and
breakpoints. See section <a href="#Annotate">Annotation Level (‘<samp>set annotate</samp>’)</a>.
</p>
</dd>
<dt> <code>-c | --command <var>cmd</var></code></dt>
<dd><a name="index-_002dc"></a>
<a name="index-_002d_002dcommand"></a>
<p>Run the string instead of running a script
</p>
</dd>
<dt> <code>-B | --basename</code></dt>
<dd><a name="index-_002dB"></a>
<a name="index-_002d_002dbasename"></a>
<p>This option causes the <acronym>BASH</acronym> debugger to print its version number and
no-warranty blurb, and exit.
</p>
</dd>
<dt> <code>-n | --nx | --no-init</code></dt>
<dd><a name="index-_002dn"></a>
<a name="index-_002d_002dnx"></a>
<a name="index-_002d_002dno_002dinit"></a>
<p>Do not execute commands found in any initialization files. Normally,
<acronym>BASH</acronym> executes the commands in these files after all the command
options and arguments have been processed. See section <a href="#Command-Files">Command files</a>.
</p>
</dd>
<dt> <code>-q | --quiet</code></dt>
<dd><a name="index-_002dq"></a>
<a name="index-_002d_002dquiet"></a>
<p>“Quiet”. Do not print the introductory and copyright messages. These
messages are also suppressed in batch mode.
</p>
</dd>
<dt> <code>-t | --terminal | --tty <var>tty</var></code></dt>
<dd><a name="index-_002dt"></a>
<a name="index-_002d_002dterminal"></a>
<a name="index-_002d_002dtty"></a>
<p>“Terminal output”. Set the file or terminal that you want debugger command
output to go to. Note that the debugger output is independent of the
debugged script output.
</p>
</dd>
<dt> <code>-x | --eval-command</code></dt>
<dd><a name="index-_002dx"></a>
<a name="index-_002d_002deval_002dcommand-cmdfile"></a>
<p>execute debugger commands from <var>cmdfile</var>.
</p></dd>
<dt> <code>-L | --library <var>directory</var></code></dt>
<dd>
<a name="index-_002dL"></a>
<a name="index-_002d_002dlibrary"></a>
<p>Set directory where debugger files reside to <var>directory</var>. The
default location is <code>../lib/bashdb</code> relative to the place that
the bashdb script is located. For example if bashdb is located in
<code>/usr/bin/bashdb</code>, the default library location will be
<code>/usr/lib/bashdb</code> which may or may not exist. If it doesn’t
you’ll get an error when you run bashdb. Only if the default location
is incorrect, should you need to use the <code>-L</code> option.
</p>
</dd>
<dt> <code>-T | --tempdir <var>directory</var></code></dt>
<dd><a name="index-_002dT"></a>
<a name="index-_002d_002dtempdir"></a>
<p>Set directory to use for writing temporary files.
</p>
</dd>
</dl>
<hr size="6">
<a name="Quitting-the-BASH-debugger"></a>
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<a name="Quitting-the-BASH-debugger-1"></a>
<h2 class="section">2.2 Quitting the BASH debugger</h2>
<a name="index-interrupt"></a>
<p>An interrupt (often <kbd>C-c</kbd>) does not exit from the <acronym>BASH</acronym> debugger, but
rather terminates the action of any the <acronym>BASH</acronym> debugger command that is in
progress and returns to the <acronym>BASH</acronym> debugger command level. Inside a debugger
command interpreter, use <code>quit</code> command (see section <a href="#Quit">Quitting the BASH debugger</a>).
</p>
<p>There way to terminate the debugger is to use the <code>kill</code>
command. This does more forceful <code>kill -9</code>. It can be used in
cases where <code>quit</code> doesn’t work.
</p>
<hr size="6">
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<a name="Calling-the-BASH-debugger-from-inside-your-program"></a>
<h2 class="section">2.3 Calling the BASH debugger from inside your program</h2>
<p>Running a program from the debugger adds a bit of overhead and slows
down your program quite a bit. Addressing this better would mean some
serious changes to <acronym>BASH</acronym> internals, and judging from experience
in other languages there still the slowdown is still noticeable. If
you have a <code>configure</code> script generated by autoconf, and you want
to stop in the middle of the script, it can take quite a while.
</p>
<p>Furthermore, by necessity, debuggers change the operation of the
program they are debugging. And this can lead to unexpected and
unwanted differences. It has happened so often that the term
“Heisenbugs” (see <a href="http://en.wikipedia.org/wiki/Heisenbug">http://en.wikipedia.org/wiki/Heisenbug</a>) was
coined to describe the situation where the addition of the use of a
debugger (among other possibilities) changes behavior of the program
so that the bug doesn’t manifest itself anymore.
</p>
<p>There is another way to get into the debugger aside from calling
<code>bashdb</code> from the outset, and this adds no overhead or slowdown
until you reach the point at which you want to start
debugging. However for this method you must change the script. Because
the debugger isn’t involved before the first call, there is no
overhead; the script will run at the same speed as if there were no
debugger up to the point where it is first invoked.
</p><table class="menu" border="0" cellspacing="0">
<tr><th colspan="3" align="left" valign="top"><pre class="menu-comment">* Debugging a Running Shell Script
</pre></th></tr><tr><td align="left" valign="top"><a href="#Program_002dControlled-Line-Tracing">2.3.2 Program-Controlled Line Tracing</a></td><td> </td><td align="left" valign="top">
</td></tr>
</table>
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</tr></table>
<h3 class="subsection">2.3.1 Debugging a Running Shell Script</h3>
<p>In this section we’ll show how to modify your script so that it enters
the debugger when you send it a signal, and then we will show how you
can call the debugger directly.
</p>
<p>In either case, you’ll need to modify the script to load some the
debugger code. The name of file to load is <code>bashdb-trace</code> and it
is located in the directory where the other bash debugger files
live. For example on GNU/Linux if it is in directory
<code>/usr/local/share/bashdb</code>, you would first add to a <acronym>BASH</acronym>
script the line:
</p>
<table><tr><td> </td><td><pre class="smallexample"> source /usr/local/share/bashdb/bashdb-trace
</pre></td></tr></table>
<p>Although I said that running under the debugger adds overhead which
slows down you program, the above command in of itself will <em>not</em>
cause any slowdown. If possible, it’s best to put this somewhere in
the main-line code rather than in a function or in a subshell. If it
is put in a function of subshell and you step outside of that,
some of the global variables set up in <code>bashdb-trace</code> may be
lost. One the other hand if you know your debugging will be confined
to just the scope of the <code>source</code> command there is no problem.
</p>
<p>Here’s a complete example. In file ‘<tt>debugit.sh</tt>’
</p><table><tr><td> </td><td><pre class="smallexample"># This is my extra debug hook
source <em>/usr/share/bashdb/bashdb-trace</em> # adjust location
echo $$
while : ; do
date=$(date)
echo "$date"
sleep 2
done
</pre></td></tr></table>
<p>Now run:
</p><table><tr><td> </td><td><pre class="smallexample"> $ <b>bash ./debugit.sh</b>
Bourne-Again Shell Debugger, release bash-3.1-0.08
Copyright 2002, 2003, 2004, 2006 Rocky Bernstein
This is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
9435
Thu Jun 19 02:43:06 EDT 2008
Thu Jun 19 02:43:08 EDT 2008
</pre></td></tr></table>
<p>Sent it an "interrupt" signal
</p><table><tr><td> </td><td><pre class="smallexample"> <b>kill -INT 9435</b>
</pre></td></tr></table>
<p>And back to the running program:
</p>
<table><tr><td> </td><td><pre class="smallexample"> Program received signal SIGINT (2)...
->0 in file `./debugit.sh' at line 251 # not sure where 251 came from!
##1 main() called from file `./debugit.sh' at line 0
bashdb<0> where
->0 in file `./debugit.sh' at line 9 # but this line number is now right
##1 main() called from file `./debugit.sh' at line 0
bashdb<1> <b>list 1</b>
1: # Set up some interrupt handlers to go into the debugger
2: source /usr/share/bashdb/bashdb-trace
3:
4: echo $$
5: while : ; do
6: date=$(date)
7: echo "$date"
8: sleep 2
9:==>done
bashdb<2> <b>step</b>
(./debugit.sh:5):
5: while : ; do
bashdb<3> <b>step</b>
(./debugit.sh:6):
6: date=$(date)
bashdb<4> <b>continue -</b>
</pre></td></tr></table>
<p>The command <code>continue -</code> not only continues execution but it
removes the debug trap allowing the program to run at full speed. It
is suitable only if there are no breakpoints that you care to stop at.
</p>
<p>By default, <code>bashdb-trace</code> sets up a handler for the ‘<samp>INT</samp>’
exception. If you down’t want this or you want enter the debugger on a
different signal to be use, <code>_Dbg_handler</code>. With this function
you can specify whether to show a call stack, stop (enter the
debugger) and/or print an indication that the a signal was seen.
</p>
<p>Here are some examples:
</p><table><tr><td> </td><td><pre class="smallexample"> _Dbg_handler INT print showstack nostop # this is the default
_Dbg_handler INT # same thing
_Dbg_hander # same thing
_Dbg_handler HUP print stop # stop in debugger when getting
</pre></td></tr></table>
<hr size="6">
<a name="Explicit-Debugging-Calls_002e"></a>
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<h4 class="subsubsection">2.3.1.1 Explicit Debugging Calls.</h4>
<p>As we saw in the last section <code>bashdb-trace</code> installs some signal
handlers. However you can make an explicit call to the debugger
</p><table><tr><td> </td><td><pre class="smallexample"> _Dbg_debugger
</pre></td></tr></table>
<p>Let’s show an example of that. We’ll even do it under a condition:
</p><table><tr><td> </td><td><pre class="smallexample"> for ((i=1; i<=10; i++)) ;
(( 5 == i )) && { _Dbg_debugger }
date=$(date)
echo "$date"
sleep 2
done
</pre></td></tr></table>
<p>The debugger will be called on the 5th iteration of this loop, when
<code>i</code> has the value 5.
</p>
<p>You can also supply the number of statements to skip and the options to
<code>_Dbg_debugger</code> just as you would to the debugger itself. All of
the options listed in <a href="#Options-for-the-bashdb-script">Command-line options for <code>bashdb</code> script</a> can be used
with the exception of <code>-c</code> (run a command) and of course you
don’t supply the name of a <acronym>BASH</acronym> script.
</p>
<p>For example to stop at the next line and suppress the banner you could
use <code>_Dbg_debugger 1 -q</code> in the above example.
</p>
<hr size="6">
<a name="Program_002dControlled-Line-Tracing"></a>
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</tr></table>
<a name="Program_002dControlled-Line-Tracing-1"></a>
<h3 class="subsection">2.3.2 Program-Controlled Line Tracing</h3>
<p>You can also turn on and off line tracing. Here’s an example
</p>
<table><tr><td> </td><td><pre class="smallexample"> source <em>path-to-program</em>/bashdb-trace # modify location
...
_Dbg_linetrace_on
for i in `seq 10` ; do
echo $i
done
_Dbg_linetrace_off
_Dbg_QUIT_ON_QUIT=1
</pre></td></tr></table>
<p>The <code>_Dbg_QUIT_ON_QUIT</code> variable make sure the program doesn’t
stay inside the debugger after it quits. It can also be set earlier in
the program.
</p>
<p>Again <code><path-to-program></code> is whatever path needed to located
<code><bashdb-trace></code>. For example it might be <code></usr/local/share></code>
on some GNU/Linux installations.
</p>
<hr size="6">
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<a name="Script-Setup-inside-the-BASH-Debugger"></a>
<h1 class="chapter">3. Script Setup inside the BASH Debugger</h1>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top"><a href="#Starting">3.1 Starting your script</a></td><td> </td><td align="left" valign="top"></td></tr>
<tr><td align="left" valign="top"><a href="#Command-Files">3.2 Command files</a></td><td> </td><td align="left" valign="top"></td></tr>
<tr><td align="left" valign="top"><a href="#Arguments">3.3 Your script’s arguments</a></td><td> </td><td align="left" valign="top"></td></tr>
<tr><td align="left" valign="top"><a href="#Input_002fOutput">3.4 Your script’s input and output</a></td><td> </td><td align="left" valign="top"></td></tr>
<tr><td align="left" valign="top"><a href="#Script_002fDebugger-Interaction">3.5 Script/Debugger Interaction</a></td><td> </td><td align="left" valign="top"> Keeping out of each other’s harm
</td></tr>
</table>
<hr size="6">
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<a name="Starting-your-script"></a>
<h2 class="section">3.1 Starting your script</h2>
<a name="index-starting"></a>
<a name="index-running"></a>
<p>After invoking the debugger you should be on the first stoppable line
of your program to be debugged. At this point you can issue debugger
commands to set breakpoints (see section <a href="#Set-Breaks">Setting breakpoints</a>), or watchpoints (see section <a href="#Set-Watchpoints">Setting watchpoints</a>), or start continue the execution of the program
(see section <a href="#Resuming-Execution">Resuming Execution</a>).
</p>
<dl compact="compact">
<dd><a name="index-restart-_005bargs_005d"></a>
<a name="index-run-_0028restart_0029"></a>
<a name="index-R-_0028restart_0029"></a>
</dd>
<dt> <code>restart <span class="roman">[</span><var>args</var><span class="roman">]</span></code></dt>
<dt> <code>run <span class="roman">[</span><var>args</var><span class="roman">]</span></code></dt>
<dt> <code>R <span class="roman">[</span><var>args</var><span class="roman">]</span></code></dt>
<dd><p>Use the <code>restart</code> command to restart your script under
the <acronym>BASH</acronym> debugger. Without any arguments, the script name and parameters
from the last invocation are used. The <acronym>BASH</acronym> debugger tries to maintain the
settings, watchpoints, breakpoints, actions and so on. Internally it
uses line numbers and filenames to record he position of interesting
places in your porgram; so if your program changes some or all of
these numbers may be off. Environment variable
<code>DBG_RESTART_FILE</code> is and a temporary file are used to signal
a restart, so you shouldn’t uset <code>DBG_RESTART_FILE</code> (or any
environment variable starting with <code>BASHDB_</code>.
</p>
</dd>
</dl>
<hr size="6">
<a name="Command-Files"></a>
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<a name="Command-files"></a>
<h2 class="section">3.2 Command files</h2>
<a name="index-command-files"></a>
<p>A command file for the <acronym>BASH</acronym> debugger is a file of lines that are the <acronym>BASH</acronym> debugger
commands. Comments (lines starting with <kbd>#</kbd>) may also be included.
An empty line in a command file does nothing; it does not mean to repeat
the last command, as it would from the terminal.
</p>
<a name="index-init-file"></a>
<a name="index-_002ebashdbinit"></a>
<a name="index-bashdb_002eini"></a>
<p>When you start the <acronym>BASH</acronym> debugger, it automatically executes commands from its
<em>init files</em>, normally called ‘<tt>.bashdbinit</tt>’<a name="DOCF3" href="#FOOT3">(3)</a>.
During startup, the <acronym>BASH</acronym> debugger does the following:
</p>
<ol>
<li>
Reads the init file (if any) in your home directory<a name="DOCF4" href="#FOOT4">(4)</a>.
</li><li>
Processes command line options and operands.
</li><li>
Reads the init file (if any) in the current working directory.
</li><li>
Reads command files specified by the ‘<samp>-x</samp>’ option.
</li></ol>
<p>The init file in your home directory can set options (such as ‘<samp>set
complaints</samp>’) that affect subsequent processing of command line options
and operands. Init files are not executed if you use the ‘<samp>-x</samp>’
option (see section <a href="#Options-for-the-bashdb-script">bashdb script options</a>).
</p>
<a name="index-init-file-name"></a>
<p>On some configurations of the <acronym>BASH</acronym> debugger, the init file is known by a
different name (these are typically environments where a specialized
form of the <acronym>BASH</acronym> debugger may need to coexist with other forms, hence a
different name for the specialized version’s init file). These are the
environments with special init file names:
</p>
<p>You can also request the execution of a command file with the
<code>source</code> command:
</p>
<dl compact="compact">
<dd><a name="index-source"></a>
</dd>
<dt> <code>source <var>filename</var></code></dt>
<dd><p>Execute the command file <var>filename</var>.
</p></dd>
</dl>
<p>The lines in a command file are executed sequentially. They are not
printed as they are executed. If there is an error, execution
proceeds to the next command in the file.
</p>
<hr size="6">
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<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Your-script_0027s-arguments"></a>
<h2 class="section">3.3 Your script’s arguments</h2>
<a name="index-arguments-_0028to-your-script_0029"></a>
<p>The arguments to your script can be specified by the arguments of the
<code>restart</code> command.
They are passed to a shell, which expands wildcard characters and
performs redirection of I/O, and thence to your script.
</p>
<p><code>restart</code> with no arguments uses the same arguments used by the previous
<code>restart</code>, or those set by the <code>set args</code> command..
</p>
<dl compact="compact">
<dd><a name="index-set-args"></a>
</dd>
<dt> <code>set args</code></dt>
<dd><p>Specify the arguments to be used if your program is rerun. If
<code>set args</code> has no arguments, <code>restart</code> executes your program
with no arguments. Once you have run your program with arguments,
using <code>set args</code> before the next <code>restart</code> is the only way to run
it again without arguments.
</p>
<a name="index-show-args"></a>
</dd>
<dt> <code>show args</code></dt>
<dd><p>Show the arguments to give your program when it is started.
</p></dd>
</dl>
<hr size="6">
<a name="Input_002fOutput"></a>
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Your-script_0027s-input-and-output"></a>
<h2 class="section">3.4 Your script’s input and output</h2>
<a name="index-redirection"></a>
<a name="index-I_002fO"></a>
<a name="index-terminal"></a>
<p>By default, the script you run under the <acronym>BASH</acronym> debugger does
input and output to the same terminal that <acronym>BASH</acronym> uses.
Before running the script to be debugged, the debugger records the tty
that was in effect. All of its output is then written to that.
However you can change this when using the ‘<samp>bashdb</samp>’ script using
the ‘<samp>-t</samp>’ option.
</p>
<dl compact="compact">
<dd><a name="index-info-terminal"></a>
</dd>
<dt> <code>info terminal</code></dt>
<dd><p>Displays information recorded by the <acronym>BASH</acronym> debugger about the terminal modes your
program is using.
</p></dd>
</dl>
<a name="index-tty"></a>
<a name="index-controlling-terminal"></a>
<p>Another way to specify where your script should do input and output is
with the <code>tty</code> command. This command accepts a file name as
argument, and causes this file to be the default for future <code>restart</code>
commands. It also resets the controlling terminal for the child
process, for future <code>restart</code> commands. For example,
</p>
<table><tr><td> </td><td><pre class="example">tty /dev/ttyb
</pre></td></tr></table>
<p>directs that processes started with subsequent <code>restart</code> commands
default to do input and output on the terminal ‘<tt>/dev/ttyb</tt>’ and have
that as their controlling terminal.
</p>
<p>An explicit redirection in <code>restart</code> overrides the <code>tty</code> command’s
effect on the input/output device, but not its effect on the controlling
terminal.
</p>
<p>When you use the <code>tty</code> command or redirect input in the <code>restart</code>
command, only the input <em>for your script</em> is affected. The input
for the <acronym>BASH</acronym> debugger still comes from your terminal.
</p>
<hr size="6">
<a name="Script_002fDebugger-Interaction"></a>
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</tr></table>
<a name="Script_002fDebugger-Interaction-1"></a>
<h2 class="section">3.5 Script/Debugger Interaction</h2>
<p>The <acronym>BASH</acronym> debugger and your program live in the same variable space so to
speak. <acronym>BASH</acronym> does not have a notion of module scoping or
lexical hiding (yet) as is found in modern programming langauges and
in modern versions of the Korn shell. This then imposes some
additional care and awareness.
</p>
<p>Most of the variables and functions used inside the <acronym>BASH</acronym> debugger start
<code>_Dbg_</code>, so please don’t use variables or functions with these
names in your program.
</p>
<p><em>Note: there are some other variables that begin with just an
underscore (<code>_</code>); over time these will be phased out. But until
then, avoid those or consult what is used by the debugger. Run
‘<samp>bashdb --debugger -c "declare -p"</samp>’ to list all the variables in
use including those used by the debugger.</em>
</p>
<p>A number of environment variables are also reserved for use; these
start with <code>DBG_</code>. For example: <code>DBG_INPUT</code>,
<code>DBG_LEVEL</code> and, <code>_Dbg_QUIT_ON_QUIT</code> (see section <a href="#Debug">Debug</a>), <code>DBG_RESTART_FILE</code> (see section <a href="#Starting">Starting</a>), to
name a few. Finally, there are some <acronym>BASH</acronym> environment
dynamic variables and these start with <code>BASH_</code>. For example
<code>BASH_SUBSHELL</code> (see section <a href="#Debug">Debug</a>), <code>BASH_COMMAND</code>
(see section <a href="#Command-Display">Command Display</a>), <code>BASH_LINENO</code>, and
<code>BASH_SOURCE</code> to name a few.
</p>
<p>Inside the debugger some variables may be redefined. In particular
<code>IFS</code> and <code>PS4</code>, and various dollar variables <code>$?</code>,
<code>$1</code>, <code>$2</code>, etc. The values before entering the debugger are
saved and those variables have their old values restroed when leaving
the debugger. However you may notice these difference in various
debugger commands. For example <code>examine PS4</code> might not return the
same value as <code>eval declare -p PS4</code>. The former is picking the debugger
value while the <code>eval</code> is careful to restore the value to what
it was before entering the debugger.
</p>
<p>In order to do its work The <acronym>BASH</acronym> debugger sets up a <code>DEBUG</code>
trap. Consequently a script shouldn’t reset this or the debugger will
lose control. The <acronym>BASH</acronym> debugger also sets up an <code>EXIT</code> handler so that
it can gain control after the script finishes. Another signal
intercepted is the an interrupt or <code>INT</code> signal. For more
information about signal handling, see section <a href="#Signals">Signals</a>
</p>
<hr size="6">
<a name="Debugger-Command-Reference"></a>
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</tr></table>
<a name="BASH-Debugger-Command-Reference"></a>
<h1 class="chapter">4. BASH Debugger Command Reference</h1>
<p>You can abbreviate the long name of the <acronym>BASH</acronym> debugger command to the first
few letters of the command name, if that abbreviation is unambiguous;
and you can repeat the <code>next</code> o r<code>step</code> commands by typing
just <RET>. Some commands which require a parameter, such as
<code>print</code> remember the argument that was given to them.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top"><a href="#Command-Syntax">4.1 Command syntax</a></td><td> </td><td align="left" valign="top"> How to give commands to the BASH debugger
</td></tr>
<tr><td align="left" valign="top"><a href="#Help">4.2 Getting help (‘<samp>help</samp>’)</a></td><td> </td><td align="left" valign="top"> How to ask for help (help)
</td></tr>
<tr><td align="left" valign="top"><a href="#Quit">4.3 Quitting the BASH debugger (‘<samp>quit</samp>’, ‘<samp>kill</samp>’)</a></td><td> </td><td align="left" valign="top"> Leaving the debugger (quit, kill)
</td></tr>
<tr><td align="left" valign="top"><a href="#Program-Information">4.5 Status and Debugger Settings (‘<samp>info</samp>’, ‘<samp>show</samp>’)</a></td><td> </td><td align="left" valign="top"> Status and Debugger settings (info, show)
</td></tr>
<tr><td align="left" valign="top"><a href="#Stopping">4.4 Stopping and Resuming Execution</a></td><td> </td><td align="left" valign="top"> Stopping and continuing (break, watch, step, cont...)
</td></tr>
<tr><td align="left" valign="top"><a href="#Stack">4.6 Examining the Stack Frame (‘<samp>where</samp>’, ‘<samp>frame</samp>’, ‘<samp>up</samp>’, ‘<samp>down</samp>’)</a></td><td> </td><td align="left" valign="top"> Examining the stack frame (where, up, down, frame)
</td></tr>
<tr><td align="left" valign="top"><a href="#List">4.7 Examining Source Files (‘<samp>list</samp>’)</a></td><td> </td><td align="left" valign="top"> Printing source files (list)
</td></tr>
<tr><td align="left" valign="top"><a href="#Edit">4.8 Editing Source files (‘<samp>edit</samp>’)</a></td><td> </td><td align="left" valign="top"> Editing source files (edit)
</td></tr>
<tr><td align="left" valign="top"><a href="#Search">4.9 Searching source files (‘<samp>search</samp>’, ‘<samp>reverse</samp>’, ‘<samp>/.../</samp>’, ‘<samp>?..?</samp>’)</a></td><td> </td><td align="left" valign="top"> Searching source files (/pat/ ?pat?)
</td></tr>
<tr><td align="left" valign="top"><a href="#Data">4.10 Examining Data (‘<samp>print</samp>’, ‘<samp>examine</samp>’, ‘<samp>info variables</samp>’)</a></td><td> </td><td align="left" valign="top"> Examining data (print, examine, info variables)
</td></tr>
<tr><td align="left" valign="top"><a href="#Evaluation_002fExecution">4.11 Running Arbitrary BASH and Shell commands (‘<samp>eval</samp>’, ‘<samp>shell</samp>’)</a></td><td> </td><td align="left" valign="top"> Arbitrary execution (eval, shell)
</td></tr>
<tr><td align="left" valign="top"><a href="#Interfacing-to-the-OS">4.12 Interfacing to the OS (‘<samp>cd</samp>’, ‘<samp>pwd</samp>’)</a></td><td> </td><td align="left" valign="top"> Interfacing to the OS (cd, pwd)
</td></tr>
<tr><td align="left" valign="top"><a href="#Auto-Display">4.13 Automatic display (‘<samp>display</samp>’, ‘<samp>undisplay</samp>’)</a></td><td> </td><td align="left" valign="top"> Executing expressions on stop (display, undisplay)
</td></tr>
<tr><td align="left" valign="top"><a href="#Controlling-bashdb">4.14 Controlling bashdb (‘<samp>set</samp>’, ‘<samp>file</samp>’, ‘<samp>prompt</samp>’, ‘<samp>history</samp>’...)</a></td><td> </td><td align="left" valign="top"> Controlling bashdb (annotate, file, prompt, history...)
</td></tr>
</table>
<hr size="6">
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<tr><td valign="middle" align="left">[<a href="#Debugger-Command-Reference" title="Previous section in reading order"> < </a>]</td>
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Command-syntax"></a>
<h2 class="section">4.1 Command syntax</h2>
<p>A <acronym>BASH</acronym> debugger command is a single line of input. There is
no limit on how long it can be. It starts with a command name, which
is followed by arguments whose meaning depends on the command name.
For example, the command <code>step</code> accepts an argument which is the
number of times to step, as in ‘<samp>step 5</samp>’. You can also use the
<code>step</code> command with no arguments. Some commands do not allow any
arguments.
</p>
<a name="index-repeating-next_002fstep-commands"></a>
<a name="index-RET-_0028repeat-last-command_0029"></a>
<p>A blank line as input to the <acronym>BASH</acronym> debugger (typing just <RET>) means to
repeat the previous next or step command.
</p>
<a name="index-_0023-_0028a-comment_0029"></a>
<a name="index-comment"></a>
<p>Any text from a <kbd>#</kbd> to the end of the line is a comment; it does
nothing. This is useful mainly in command files (see section <a href="#Command-Files">Command files</a>).
</p>
<hr size="6">
<a name="Help"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Command-Syntax" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#Quit" title="Next section in reading order"> > </a>]</td>
<td valign="middle" align="left"> </td>
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</tr></table>
<a name="Getting-help-_0028help_0029"></a>
<h2 class="section">4.2 Getting help (‘<samp>help</samp>’)</h2>
<a name="index-online-documentation"></a>
<p>Once inside the <acronym>BASH</acronym> debugger, you can always ask it for
information on its commands, using the command <code>help</code>.
</p>
<dl compact="compact">
<dd><a name="index-h-_0028help_0029"></a>
</dd>
<dt> <code>help</code></dt>
<dt> <code>h</code></dt>
<dd><p>You can use <code>help</code> (abbreviated <code>h</code>) with no arguments to
display a short list of named classes of commands:
</p></dd>
</dl>
<table><tr><td> </td><td><pre class="smallexample">bashdb<0> <b>help</b>
Available commands:
/ debug enable help next show step- untrace
alias delete eval history print signal tbreak up
break disable examine info pwd skip trace watch
commands display file kill quit source tty where
condition down frame list restart step unalias
continue edit handle load set step+ undisplay
Readline command line editing (emacs/vi mode) is available.
Type "help" followed by command name for full documentation.
</pre></td></tr></table>
<dl compact="compact">
<dt> <code>help <var>command</var></code></dt>
<dd><p>With a command name as <code>help</code> argument, the <acronym>BASH</acronym>
debugger displays short information on how to use that command.
</p>
<table><tr><td> </td><td><pre class="example">bashdb<0> <b>help list</b>
l linespec List window lines starting at linespec.
l min incr List incr lines starting at 'min' linespec.
l List next window of lines.
l . Same as above.
Long command name: list.
</pre></td></tr></table>
<p>In addition to <code>help</code>, you can use the debugger command
<code>info</code> to inquire about the state of your script, or the state of
the <acronym>BASH</acronym> debugger itself. The listings under <code>info</code> in the Index
point to all the sub-commands. See section <a href="#Command-Index">Command Index</a>.
</p></dd>
</dl>
<dl compact="compact">
<dd><a name="index-info"></a>
<a name="index-i-_0028info_0029"></a>
</dd>
<dt> <code>info</code></dt>
<dd><p>This command (abbreviated <code>i</code>) is for describing the state of
your program. For example, you can list the arguments given to your
script with <code>info args</code>, or list the breakpoints you have set
with <code>info breakpoints</code>. You can get a complete list of the
<code>info</code> sub-commands with <code>help info</code>.
</p>
<table><tr><td> </td><td><pre class="example">bashdb<0> <b>help info</b>
List of info subcommands:
info args -- Argument variables (e.g. $1, $2, ...) of the current stack frame.
info breakpoints -- Status of user-settable breakpoints
info display -- Show all display expressions
info files -- Source files in the program
info functions -- All function names
info line -- list current line number and and file name
info program -- Execution status of the program.
info signals -- What debugger does when program gets various signals
info source -- Information about the current source file
info stack -- Backtrace of the stack
info terminal -- Print terminal device
info variables -- All global and static variable names
info warranty -- Various kinds of warranty you do not have
bashdb<1> <b>info source</b>
Current script file is parm.sh
Contains 34 lines.
</pre></td></tr></table>
</dd>
</dl>
<hr size="6">
<a name="Quit"></a>
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<tr><td valign="middle" align="left">[<a href="#Help" title="Previous section in reading order"> < </a>]</td>
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<a name="Quitting-the-BASH-debugger-_0028quit_002c-kill_0029"></a>
<h2 class="section">4.3 Quitting the BASH debugger (‘<samp>quit</samp>’, ‘<samp>kill</samp>’)</h2>
<dl compact="compact">
<dd><a name="index-quit-_005bexpression-_005bsubshell_002dlevels_005d_005d"></a>
<a name="index-q-_0028quit_0029"></a>
</dd>
<dt> <code>quit <span class="roman">[</span><var>expression</var><span class="roman">]</span></code></dt>
<dt> <code>quit <span class="roman">[</span><var>expression</var> <span class="roman">[</span><var>subshell-levels</var><span class="roman">]</span><span class="roman">]</span></code></dt>
<dt> <code>q</code></dt>
<dd>
<p>To exit the <acronym>BASH</acronym> debugger, use the <code>quit</code> command (abbreviated
<code>q</code>), or type an end-of-file character (usually <kbd>C-d</kbd>). If
you do not supply <var>expression</var>, the <acronym>BASH</acronym> debugger will try to terminate
normally or with exit code 0. Otherwise it will terminate using the
result of <var>expression</var> as the exit code.
</p>
<p>A simple <code>quit</code> tries to terminate all nested subshells that may
be in effect. If you are nested a subshell, this is normally
indicated in a debugger prompt by the number of parentheses that the
history number is inside — no parenthesis means there is no subshell
in effect. The dynamic variable <code>BASH_SUBSHELL</code> also contains the
number of subshells in effect.
</p>
<p>If you want only to terminate some number of subshells but not all of
them, you can give a count of the number of subshells to leave after
the return-code expression. To leave just one level of subshell
<code>return</code> does almost the same thing. (See see section <a href="#Returning">Returning</a>) There is a subtle difference between the two though:
<code>return</code> will leave you at the beginning of the next statement
while <code>quit</code> may leave you at the place the subshell was invoked
which may be in the middle of another command such as an assingment
statement or condition test.
</p>
<p>If the environment variable <code>_Dbg_QUIT_ON_QUIT</code> is set, when the
program terminates, the debugger will also terminate too. This may be
useful if you are debugging a script which calls another script and
you want this inner script just to return to the outer script.
</p>
</dd>
<dt> <code>kill</code></dt>
<dd><a name="index-k-_0028kill_0029"></a>
</dd>
<dt> <code>k</code></dt>
<dd><p>In situations where <code>quit</code> doesn’t work we provide an alternative
and more forceful quit command: <code>kill</code>. This sends to the OS
non-maskable KILL signal with the debugger process number. No cleanup
of temporary files is done by the program.
</p></dd>
</dl>
<hr size="6">
<a name="Stopping"></a>
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<a name="Stopping-and-Resuming-Execution"></a>
<h2 class="section">4.4 Stopping and Resuming Execution</h2>
<p>One important use of a debugger is to stop your program <em>before</em> it
terminates so that if your script might run into trouble, you can
investigate and find out why. However should your script accidently
continue to termination, the <acronym>BASH</acronym> debugger has arranged for it not to leave the
debugger without your explicit instruction. That way, you can restart
the program using the same command arguments.
</p>
<p>Inside the <acronym>BASH</acronym> debugger, your script may stop for any of several reasons,
such as a signal, a breakpoint, or reaching a new line after a
debugger command such as <code>step</code>. You may then examine and
change variables, set new breakpoints or remove old ones, and then
continue execution.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top"><a href="#Breakpoints">4.4.1 Breakpoints, watchpoints (‘<samp>break</samp>’, ‘<samp>tbreak</samp>’, ‘<samp>watch</samp>’, ‘<samp>watche</samp>’...)</a></td><td> </td><td align="left" valign="top"> Breakpoints, watchpoints (break, tbreak, watch, watche, clear)
</td></tr>
<tr><td align="left" valign="top"><a href="#Resuming-Execution">4.4.2 Resuming Execution (‘<samp>step</samp>’, ‘<samp>next</samp>’, ‘<samp>finish</samp>’, ‘<samp>skip</samp>’, ‘<samp>continue</samp>’, ‘<samp>debug</samp>’, ‘<samp>return</samp>’)</a></td><td> </td><td align="left" valign="top"> Resuming execution (continue, step, next, skip, finish, return, debug)
</td></tr>
<tr><td align="left" valign="top"><a href="#Signals">4.4.3 Signals (‘<samp>handle</samp>’, ‘<samp>info handle</samp>’, ‘<samp>signal</samp>’)</a></td><td> </td><td align="left" valign="top"> Signals
</td></tr>
</table>
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<a name="Breakpoints_002c-watchpoints-_0028break_002c-tbreak_002c-watch_002c-watche_002e_002e_002e_0029"></a>
<h3 class="subsection">4.4.1 Breakpoints, watchpoints (‘<samp>break</samp>’, ‘<samp>tbreak</samp>’, ‘<samp>watch</samp>’, ‘<samp>watche</samp>’...)</h3>
<a name="index-breakpoints"></a>
<p>A <em>breakpoint</em> makes your script stop whenever a certain point in
the program is reached. For each breakpoint, you can add conditions to
control in finer detail whether your script stops.
</p>
<p>You specify the place where your script should stop with the <code>break</code>
command and its variants (see section <a href="#Set-Breaks">Setting breakpoints</a>). These commands allow own to specify the location by
line number and file name or function name.
</p>
<a name="index-watchpoints"></a>
<a name="index-breakpoint-on-variable-modification"></a>
<p>A <em>watchpoint</em> is a special breakpoint that stops your script when
the value of an expression changes. There is a different command to
set watchpoints (see section <a href="#Set-Watchpoints">Setting watchpoints</a>).
</p>
<p>But aside from that, you can manage a watchpoint like any other
breakpoint: you delete enable, and disable both breakpoints and
watchpoints using the same commands.
</p>
<p>You can arrange to have values from your program displayed automatically
whenever <acronym>BASH</acronym> stops at a breakpoint. See section <a href="#Auto-Display">Automatic display</a>.
</p>
<a name="index-breakpoint-numbers"></a>
<a name="index-numbers-for-breakpoints"></a>
<p>The <acronym>BASH</acronym> debugger assigns a number to each breakpoint when you create it;
these numbers are successive integers starting with one. In many of
the commands for controlling various features of breakpoints you use
the breakpoint number to say which breakpoint you want to change.
Each breakpoint may be <em>enabled</em> or <em>disabled</em>; if disabled,
it has no effect on your script until you enable it again.
</p>
<a name="index-watchpoints-numbers"></a>
<a name="index-numbers-for-watchpoints"></a>
<p>Watchpoint numbers however are distinguished from breakpoint numbers by
virtue of their being suffixed with the either an upper- or lower-case
‘W’. For example, to enable breakpoint entry 0 along with watchpoint
entry 1 you would write ‘<samp>enable 1 2w</samp>’, the “2w” refers to the
watchpoint; “2W” would work just as well.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top"><a href="#Set-Breaks">4.4.1.1 Setting breakpoints (‘<samp>break</samp>’ ‘<samp>tbreak</samp>’)</a></td><td> </td><td align="left" valign="top"> Setting breakpoints (break, tbreak)
</td></tr>
<tr><td align="left" valign="top"><a href="#Set-Watchpoints">4.4.1.2 Setting watchpoints (‘<samp>watch</samp>’, ‘<samp>watche</samp>’)</a></td><td> </td><td align="left" valign="top"> Setting watchpoints (watch, watche)
</td></tr>
<tr><td align="left" valign="top"><a href="#Break-Commands">4.4.1.3 Breakpoint command lists (‘<samp>commands</samp>’)</a></td><td> </td><td align="left" valign="top"> Breakpoint command lists (command)
</td></tr>
<tr><td align="left" valign="top"><a href="#Delete-Breaks">4.4.1.4 Deleting breakpoints (‘<samp>clear</samp>’, ‘<samp>delete</samp>’)</a></td><td> </td><td align="left" valign="top"> Deleting breakpoints (delete, clear)
</td></tr>
<tr><td align="left" valign="top"><a href="#Disabling">4.4.1.5 Disabling breakpoints (‘<samp>disable</samp>’, ‘<samp>enable</samp>’)</a></td><td> </td><td align="left" valign="top"> Disabling breakpoints (disable, enable)
</td></tr>
<tr><td align="left" valign="top"><a href="#Conditions">4.4.1.6 Break conditions (‘<samp>condition</samp>’)</a></td><td> </td><td align="left" valign="top"> Break conditions (condition)
</td></tr>
</table>
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<a name="Setting-breakpoints-_0028break-tbreak_0029"></a>
<h4 class="subsubsection">4.4.1.1 Setting breakpoints (‘<samp>break</samp>’ ‘<samp>tbreak</samp>’)</h4>
<a name="index-break"></a>
<a name="index-b-_0028break_0029"></a>
<a name="index-latest-breakpoint"></a>
<p>Breakpoints are set with the <code>break</code> command (abbreviated
<code>b</code>).
</p>
<dl compact="compact">
<dt> <code>break <var>function</var></code></dt>
<dd><p>Set a breakpoint at entry to function <var>function</var>.
</p>
</dd>
<dt> <code>break <var>linenum</var></code></dt>
<dd><p>Set a breakpoint at line <var>linenum</var> in the current source file.
The current source file is the last file whose source text was printed.
The breakpoint will stop your script just before it executes any of the
code on that line.
</p>
</dd>
<dt> <code>break <var>filename</var>:<var>linenum</var></code></dt>
<dd><p>Set a breakpoint at line <var>linenum</var> in source file <var>filename</var>;
<var>filename</var> has to be one of the files previously read in and has
to be specified exactly as the name used when read in. For a list of
read-in files, use the ‘<samp>info files</samp>’ command.
</p>
</dd>
<dt> <code>break … if <var>cond</var></code></dt>
<dd><p>Set a breakpoint with condition <var>cond</var>; evaluate the expression
<var>cond</var> each time the breakpoint is reached, and stop only if the
value is nonzero—that is, if <var>cond</var> evaluates as true. The
expression is evaluated via the <code>let</code> builtin funtion.
‘<samp>…</samp>’ stands for one of the possible arguments described
above (or no argument) specifying where to break. The word “if” is
often optional and is necessary only ‘<samp>…</samp>’ is
omitted. See section <a href="#Conditions">Break conditions</a>, for more information on
breakpoint conditions.
</p>
<p>Examples:
</p><table><tr><td> </td><td><pre class="example">bashdb<0> <b>break fn1</b>
Breakpoint 1 set in file parm.sh, line 3.
bashdb<1> <b>break 28</b>
Breakpoint 2 set in file parm.sh, line 28.
bashdb<2> <b>break parm.sh:29</b>
Breakpoint 3 set in file parm.sh, line 29.
bashdb<3> <b>break 28 if x==5</b>
Breakpoint 4 set in file parm.sh, line 28.
</pre></td></tr></table>
<a name="index-tbreak"></a>
</dd>
<dt> <code>tbreak <var>args</var></code></dt>
<dd><p>Set a breakpoint enabled only for one stop. <var>args</var> are the
same as for the <code>break</code> command, and the breakpoint is set in the same
way, but the breakpoint is automatically deleted after the first time your
program stops there. See section <a href="#Disabling">Disabling breakpoints</a>.
</p>
<a name="index-info-breakpoints"></a>
<a name="index-_0024_005f-and-info-breakpoints"></a>
</dd>
<dt> <code>info breakpoints <span class="roman">[</span><var>n</var><span class="roman">]</span></code></dt>
<dt> <code>info break <span class="roman">[</span><var>n</var><span class="roman">]</span></code></dt>
<dt> <code>info watchpoints <span class="roman">[</span><var>n</var><span class="roman">]</span></code></dt>
<dd><p>Print a table of all breakpoints, watchpoints set and not deleted,
with the following columns for each breakpoint:
</p>
<dl compact="compact">
<dt> <em>Breakpoint Numbers (‘<samp>Num</samp>’)</em></dt>
<dt> <em>Enabled or Disabled (‘<samp>Enb</samp>’)</em></dt>
<dd><p>Enabled breakpoints are marked with ‘<samp>1</samp>’. ‘<samp>0</samp>’ marks breakpoints
that are disabled (not enabled).
</p></dd>
<dt> <em>Count</em></dt>
<dd><p>The number of times that breakpoint or watchpoint has been hit.
</p></dd>
<dt> <em>File and Line (‘<samp>file:line</samp>’)</em></dt>
<dd><p>The filename and line number inside that file where of breakpoint in
the script. The file and line are separated with a colon.
</p></dd>
<dt> <em>Condition</em></dt>
<dd><p>A condition (an arithmetic expression) which when true causes the
breakpoint to take effect.
</p></dd>
</dl>
<p>If a breakpoint is conditional, <code>info break</code> shows the condition on
the line following the affected breakpoint; breakpoint commands, if any,
are listed after that.
</p>
<p><code>info break</code> displays a count of the number of times the breakpoint
has been hit.
</p>
<p><code>info break</code> with a breakpoint number <var>n</var> as argument lists
only that breakpoint.
</p>
<p>Examples:
</p><table><tr><td> </td><td><pre class="example">bashdb<4> <b>info break</b>
Breakpoints at following places:
Num Type Disp Enb What
1 breakpoint keep y parm.sh:3
2 breakpoint keep y parm.sh:28
3 breakpoint keep y parm.sh:29
4 breakpoint keep y parm.sh:28
No watch expressions have been set.
bashdb<5> <b>info break 4</b>
Num Type Disp Enb What
4 breakpoint keep y parm.sh:28
No watch expressions have been set.
</pre></td></tr></table>
</dd>
</dl>
<p>the <acronym>BASH</acronym> debugger allows you to set any number of breakpoints at the same place in
your script. There is nothing silly or meaningless about this. When
the breakpoints are conditional, this is even useful
(see section <a href="#Conditions">Break conditions</a>).
</p>
<hr size="6">
<a name="Set-Watchpoints"></a>
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<a name="Setting-watchpoints-_0028watch_002c-watche_0029"></a>
<h4 class="subsubsection">4.4.1.2 Setting watchpoints (‘<samp>watch</samp>’, ‘<samp>watche</samp>’)</h4>
<a name="index-setting-watchpoints"></a>
<p>You can use a watchpoint to stop execution whenever the value of an
expression changes, without having to predict a particular place where
this may happen. As with the <code>print</code> (see section <a href="#Data">Examining Data</a>), the idiosyncracies of a <acronym>BASH</acronym> or any POSIX shell
derivative suggest using two commands. The <code>watch</code> command is
just for a single variables; the <code>watche</code> command uses the
builtin “let” command to evaluate an expression. If the variable you
are tracking can take a string value, issuing something like
‘<samp>watch foo</samp>’ will not have the desired effect—any string
assignment to <code>foo</code> will have a value 0 when it is assigned via
“let.”
</p>
<dl compact="compact">
<dd><a name="index-watch"></a>
</dd>
<dt> <code>watch <var>var</var></code></dt>
<dd><p>Set a watchpoint for a variable. the <acronym>BASH</acronym> debugger will break when the
value of <var>var</var> changes. In this command do not add a leading
dollar symbol to <var>var</var>.
</p>
</dd>
<dt> <code>watche <var>expr</var></code></dt>
<dd><p>Set a watchpoint for an expression via the builtin “let” command.
the <acronym>BASH</acronym> debugger will break when <var>expr</var> is written into by the program
and its value changes. Not that this may not work for tracking
arbitrary string value changes. For that use <code>watch</code> described
earlier.
</p></dd>
</dl>
<hr size="6">
<a name="Break-Commands"></a>
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<a name="Breakpoint-command-lists-_0028commands_0029"></a>
<h4 class="subsubsection">4.4.1.3 Breakpoint command lists (‘<samp>commands</samp>’)</h4>
<dl compact="compact">
<dd><a name="index-commands"></a>
<a name="index-end"></a>
</dd>
<dt> <code>commands <span class="roman">[</span><var>bnum</var><span class="roman">]</span></code></dt>
<dt> <code>… <var>command-list</var> …</code></dt>
<dt> <code>end</code></dt>
<dd><p>Specify a list of commands for breakpoint number <var>bnum</var>. The commands
themselves appear on the following lines. Type a line containing just
<code>end</code> to terminate the commands.
</p>
<p>To remove all commands from a breakpoint, type <code>commands</code> and
follow it immediately with <code>end</code>; that is, give no commands.
</p>
<p>With no <var>bnum</var> argument, <code>commands</code> refers to the last
breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
recently encountered).
</p></dd>
</dl>
<p>Pressing <RET> as a means of repeating the last debugger command is
disabled within a <var>command-list</var>.
</p>
<p>You can use breakpoint commands to start your program up again. Simply
use the <code>continue</code> command, or <code>step</code>, or any other command
that resumes execution.
</p>
<p>Any other commands in the command list, after a command that resumes
execution, are ignored. This is because any time you resume execution
(even with a simple <code>next</code> or <code>step</code>), you may encounter
another breakpoint—which could have its own command list, leading to
ambiguities about which list to execute.
</p>
<a name="index-silent"></a>
<p>If the first command you specify in a command list is <code>silent</code>, the
usual message about stopping at a breakpoint is not printed. This may
be desirable for breakpoints that are to print a specific message and
then continue. If none of the remaining commands print anything, you
see no sign that the breakpoint was reached. <code>silent</code> is
meaningful only at the beginning of a breakpoint command list.
</p>
<p>The commands <code>echo</code>, <code>output</code>, and <code>printf</code> allow you to
print precisely controlled output, and are often useful in silent
breakpoints.
</p>
<p>For example, here is how you could use breakpoint commands to print the
value of <code>x</code> at entry to <code>foo</code> whenever <code>x</code> is positive.
</p>
<table><tr><td> </td><td><pre class="smallexample">break foo if x>0
commands
silent
printf "x is %d\n",x
cont
end
</pre></td></tr></table>
<p>One application for breakpoint commands is to compensate for one bug so
you can test for another. Put a breakpoint just after the erroneous line
of code, give it a condition to detect the case in which something
erroneous has been done, and give it commands to assign correct values
to any variables that need them. End with the <code>continue</code> command
so that your program does not stop, and start with the <code>silent</code>
command so that no output is produced. Here is an example:
</p>
<table><tr><td> </td><td><pre class="smallexample">break 403
commands
silent
set x = y + 4
cont
end
</pre></td></tr></table>
<hr size="6">
<a name="Delete-Breaks"></a>
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<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Function-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Deleting-breakpoints-_0028clear_002c-delete_0029"></a>
<h4 class="subsubsection">4.4.1.4 Deleting breakpoints (‘<samp>clear</samp>’, ‘<samp>delete</samp>’)</h4>
<a name="index-clearing-breakpoints_002c-watchpoints"></a>
<a name="index-deleting-breakpoints_002c-watchpoints"></a>
<p>It may desirable to eliminate a breakpoint or watchpoint once it
has done its job and you no longer want your script to stop there.
This is called <em>deleting</em> the breakpoint. A breakpoint that has
been deleted no longer exists; it is forgotten.
</p>
<p>With the <code>clear</code> command you can delete breakpoints according to
where they are in your script. With the <code>delete</code> command you can
delete individual breakpoints, or watchpoints by specifying their
breakpoint numbers. <em>Note: as described below under the “clear”
command, “d” is an alias for “clear”, not “delete”. </em>
</p>
<p>It is not necessary to delete a breakpoint to proceed past it. the <acronym>BASH</acronym> debugger
automatically ignores breakpoints on the first instruction to be executed
when you continue execution.
</p>
<dl compact="compact">
<dd><a name="index-clear"></a>
<a name="index-d-_0028clear_0029"></a>
</dd>
<dt> <code>clear</code></dt>
<dd><p>Delete any breakpoints at the next instruction to be executed in the
selected stack frame (see section <a href="#Selection">Selecting a frame</a>). When
the innermost frame is selected, this is a good way to delete a
breakpoint where your script just stopped.
</p>
<p>It may seem odd that we have an alias “d” for “clear.” It so
happens that Perl’s debugger use “d” for its delete command and the
delete concept in Perl’s debugger corresponds to “clear” in
GDB. (Perl doesn’t have a notion of breakpoint entry numbers). So in
order to be compatible with both debugger interfaces, “d” is used as
an alias for “clear.” Clear?
</p>
</dd>
<dt> <code>clear <var>function</var></code></dt>
<dt> <code>clear <var>filename</var>:<var>function</var></code></dt>
<dd><p>Delete any breakpoints set at entry to the function <var>function</var>.
</p>
</dd>
<dt> <code>clear <var>linenum</var></code></dt>
<dt> <code>d <var>linenum</var></code></dt>
<dd><p>Delete any breakpoints set at or within the code of the specified line.
</p>
<a name="index-delete-breakpoints"></a>
<a name="index-delete"></a>
<a name="index-de-_0028delete_0029"></a>
</dd>
<dt> <code>delete <span class="roman">[</span><var>breakpoints</var><span class="roman">]</span></code></dt>
<dd><p>Delete the breakpoints, watchpoints specified as arguments.
</p>
<p>If no argument is specified, delete all breakpoints (the <acronym>BASH</acronym> debugger asks
confirmation, unless you have <code>set confirm off</code>). You can
abbreviate this command as <code>de</code>.
</p>
<p>Note that for compatibility with Perl’s debugger, <code>d</code> means
something else: <code>clear</code>.
</p>
</dd>
</dl>
<hr size="6">
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<a name="Disabling-breakpoints-_0028disable_002c-enable_0029"></a>
<h4 class="subsubsection">4.4.1.5 Disabling breakpoints (‘<samp>disable</samp>’, ‘<samp>enable</samp>’)</h4>
<p>Rather than deleting a breakpoint or watchpoint, you might
prefer to <em>disable</em> it. This makes the breakpoint inoperative as if
it had been deleted, but remembers the information on the breakpoint so
that you can <em>enable</em> it again later.
</p>
<p>You disable and enable breakpoints, watchpoints, and catchpoints with
the <code>enable</code> and <code>disable</code> commands, optionally specifying one
or more breakpoint numbers as arguments. Use <code>info break</code> or
<code>info watch</code> to print a list of breakpoints, watchpoints, and
catchpoints if you do not know which numbers to use.
</p>
<p>A breakpoint, watchpoint, or catchpoint can have any of four different
states of enablement:
</p>
<ul>
<li>
Enabled. The breakpoint stops your program. A breakpoint set
with the <code>break</code> command starts out in this state.
</li><li>
Disabled. The breakpoint has no effect on your program.
</li><li>
Enabled once. The breakpoint stops your program, but then becomes
disabled.
</li><li>
Enabled for deletion. The breakpoint stops your program, but
immediately after it does so it is deleted permanently. A breakpoint
set with the <code>tbreak</code> command starts out in this state.
</li></ul>
<p>You can use the following commands to enable or disable breakpoints,
watchpoints, and catchpoints:
</p>
<dl compact="compact">
<dd><a name="index-disable-breakpoints"></a>
<a name="index-disable"></a>
<a name="index-dis-_0028disable_0029"></a>
</dd>
<dt> <code>disable <span class="roman">[</span><var>breakpoints</var><span class="roman">]</span></code></dt>
<dd><p>Disable the specified breakpoints—or all breakpoints, if none are
listed. A disabled breakpoint has no effect but is not forgotten. All
options such as ignore-counts, conditions and commands are remembered in
case the breakpoint is enabled again later. You may abbreviate
<code>disable</code> as <code>dis</code>.
</p>
<a name="index-enable-breakpoints"></a>
<a name="index-enable"></a>
</dd>
<dt> <code>enable <span class="roman">[</span><var>breakpoints</var><span class="roman">]</span></code></dt>
<dd><p>Enable the specified breakpoints (or all defined breakpoints). They
become effective once again in stopping your program.
</p></dd>
</dl>
<p>Except for a breakpoint set with <code>tbreak</code> (see section <a href="#Set-Breaks">Setting breakpoints</a>), breakpoints that you set are initially enabled;
subsequently, they become disabled or enabled only when you use one of
the commands above. (The command <code>until</code> can set and delete a
breakpoint of its own, but it does not change the state of your other
breakpoints; see <a href="#Resuming-Execution">Resuming Execution</a>.)
</p>
<hr size="6">
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<a name="Break-conditions-_0028condition_0029"></a>
<h4 class="subsubsection">4.4.1.6 Break conditions (‘<samp>condition</samp>’)</h4>
<a name="index-conditional-breakpoints"></a>
<a name="index-breakpoint-conditions"></a>
<p>The simplest sort of breakpoint breaks every time your script reaches
a specified place. You can also specify a <em>condition</em> for a
breakpoint. A condition is just a <acronym>BASH</acronym> expression.
</p>
<p>Break conditions can be specified when a breakpoint is set, by using
‘<samp>if</samp>’ in the arguments to the <code>break</code> command. See section <a href="#Set-Breaks">Setting breakpoints</a>. A breakpoint with a condition
evaluates the expression each time your script reaches it, and your
script stops only if the condition is <em>true</em>. They can also be
changed at any time with the <code>condition</code> command.
</p>
<a name="index-one_002dtime-breakpoints"></a>
<p>There is also a notion of a “one-time” breakpoint which gets deleted
as soon as it is hit, so that that breakpoint is executed once only.
</p>
<p>Conditions are also accepted for watchpoints; you may not need them,
since a watchpoint is inspecting the value of an expression anyhow—but
it might be simpler, say, to just set a watchpoint on a variable name,
and specify a condition that tests whether the new value is an interesting
one.
</p>
<dl compact="compact">
<dd><a name="index-condition"></a>
</dd>
<dt> <code>condition <var>bnum</var> <var>expression</var></code></dt>
<dd><p>Specify <var>expression</var> as the break condition for breakpoint
<var>bnum</var>. After you set a condition, breakpoint <var>bnum</var> stops
your program only if the value of <var>expression</var> is true (nonzero).
</p>
</dd>
<dt> <code>condition <var>bnum</var></code></dt>
<dd><p>Remove the condition from breakpoint number <var>bnum</var>. It becomes
an ordinary unconditional breakpoint.
</p></dd>
</dl>
<p><acronym>BASH</acronym> does
not actually evaluate <var>expression</var> at the time the <code>condition</code>
command (or a command that sets a breakpoint with a condition, like
<code>break if …</code>) is given, however.
</p>
<p>Examples;
</p><table><tr><td> </td><td><pre class="example">condition 1 x>5 # Stop on breakpoint 0 only if x>5 is true.
condition 1 # Change that! Unconditinally stop on breakpoint 1.
</pre></td></tr></table>
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<a name="Resuming-Execution-_0028step_002c-next_002c-finish_002c-skip_002c-continue_002c-debug_002c-return_0029"></a>
<h3 class="subsection">4.4.2 Resuming Execution (‘<samp>step</samp>’, ‘<samp>next</samp>’, ‘<samp>finish</samp>’, ‘<samp>skip</samp>’, ‘<samp>continue</samp>’, ‘<samp>debug</samp>’, ‘<samp>return</samp>’)</h3>
<p>A typical technique for using stepping is to set a breakpoint
(see section <a href="#Breakpoints">Breakpoints; watchpoints</a>) at the
beginning of the function or the section of your script where a problem
is believed to lie, run your script until it stops at that breakpoint,
and then step through the suspect area, examining the variables that are
interesting, until you see the problem happen.
</p>
<a name="index-stepping"></a>
<a name="index-continuing"></a>
<a name="index-resuming-execution"></a>
<p><em>Continuing</em> means resuming program execution until your script
completes normally. In contrast, <em>stepping</em> means executing just
one more “step” of your script, where “step” may mean either one
line of source code. Either when continuing or when stepping,
your script may stop even sooner, due to a breakpoint or a signal.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top"><a href="#Step">4.4.2.1 Step (‘<samp>step</samp>’)</a></td><td> </td><td align="left" valign="top"> running the next statement (step)
</td></tr>
<tr><td align="left" valign="top"><a href="#Next">4.4.2.2 Next (‘<samp>next</samp>’)</a></td><td> </td><td align="left" valign="top"> running the next statement skipping over functions (next)
</td></tr>
<tr><td align="left" valign="top"><a href="#Finish">4.4.2.3 Finish (‘<samp>finish</samp>’)</a></td><td> </td><td align="left" valign="top"> running until the return of a function or “source” (finish)
</td></tr>
<tr><td align="left" valign="top"><a href="#Skip">4.4.2.4 Skip (‘<samp>skip</samp>’)</a></td><td> </td><td align="left" valign="top"> skipping the next statement (skip)
</td></tr>
<tr><td align="left" valign="top"><a href="#Continue">4.4.2.5 Continue (‘<samp>continue</samp>’)</a></td><td> </td><td align="left" valign="top"> continuing execution (continue)
</td></tr>
<tr><td align="left" valign="top"><a href="#Debug">4.4.2.6 Debug (‘<samp>debug</samp>’)</a></td><td> </td><td align="left" valign="top"> debugging into another program (debug)
</td></tr>
<tr><td align="left" valign="top"><a href="#Returning">4.4.2.7 Returning from a function, sourced file, or subshell (‘<samp>return</samp>’)</a></td><td> </td><td align="left" valign="top"> returning
</td></tr>
</table>
<hr size="6">
<a name="Step"></a>
<table cellpadding="1" cellspacing="1" border="0">
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<a name="Step-_0028step_0029"></a>
<h4 class="subsubsection">4.4.2.1 Step (‘<samp>step</samp>’)</h4>
<dl compact="compact">
<dd><a name="index-step"></a>
<a name="index-s-_0028step_0029"></a>
</dd>
<dt> <code>step<span class="roman">[</span><var>+|-</var><span class="roman">]</span> <span class="roman">[</span><var>count</var><span class="roman">]</span></code></dt>
<dd><p>Continue running your script until control reaches a different source
line, then stop it and return control to the <acronym>BASH</acronym> debugger. An default
alias alias for this is <code>s</code>.
</p>
<p>The <code>step</code> command only stops at the first instruction of a source
line. This prevents the multiple stops that could otherwise occur in
<code>switch</code> statements, <code>for</code> loops, etc. <code>step</code> continues
to stop if a function that has debugging information is called within
the line. In other words, <code>step</code> <em>steps inside</em> any functions
called within the line.
</p>
<p>Sometimes you want to step ensure that the next line is different from
the one you currently are on. To do this, add the <code>+</code> suffix. And
if you find you want to do this all of the time there is a setting
<code>force</code> that will have this be the default behavior. On the other
hand if you want to be explicit about not having this behavior even
when <code>force</code> is in effect add the <code>-</code> suffix.
</p>
<p>With a count, continue running as in <code>step</code>, but do so
<var>count</var> times. If a breakpoint is reached, or a signal not
related to stepping occurs before <var>count</var> steps, stepping stops
right away.
</p></dd>
</dl>
<hr size="6">
<a name="Next"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Step" title="Previous section in reading order"> < </a>]</td>
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<a name="Next-_0028next_0029"></a>
<h4 class="subsubsection">4.4.2.2 Next (‘<samp>next</samp>’)</h4>
<dl compact="compact">
<dd><a name="index-next"></a>
<a name="index-n-_0028next_0029"></a>
</dd>
<dt> <code>next <span class="roman">[</span><var>count</var><span class="roman">]</span></code></dt>
<dd><p>Continue to the next source line in the current (innermost) stack frame.
This is similar to <code>step</code>, but function calls that appear within
the line of code are executed without stopping. Execution stops when
control reaches a different line of code at the original stack level
that was executing when you gave the <code>next</code> command. This command
is abbreviated <code>n</code>.
</p>
<p>An argument <var>count</var> is a repeat count, as for <code>step</code>.
</p></dd>
</dl>
<hr size="6">
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<a name="Finish-_0028finish_0029"></a>
<h4 class="subsubsection">4.4.2.3 Finish (‘<samp>finish</samp>’)</h4>
<dl compact="compact">
<dd><a name="index-finish"></a>
</dd>
<dt> <code>finish</code></dt>
<dd><p>Continue running until just after function returns. <em>Currently,
the line shown on a return is the function header, unless the
<code>return</code> builtin function is executed in which case it is the
line number of the <code>return</code> function.</em>
</p>
<p>Contrast this with the <code>return</code> command (see section <a href="#Returning">Returning from a function</a>) and the <code>quit</code> (see section <a href="#Quitting-the-BASH-debugger">Quitting the BASH debugger</a>).
</p>
</dd>
</dl>
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<a name="Skip-_0028skip_0029"></a>
<h4 class="subsubsection">4.4.2.4 Skip (‘<samp>skip</samp>’)</h4>
<dl compact="compact">
<dd><a name="index-skip"></a>
</dd>
<dt> <code>skip <span class="roman">[</span><var>count</var><span class="roman">]</span></code></dt>
<dd><p>Skip execution of the next source line.
This may be useful if you have an action that “fixes” existing code in
the script. The <code>debug</code> command internally uses the <code>skip</code> command
to skip over existing non-debugged invocation that was presumably just
run.
</p></dd>
</dl>
<hr size="6">
<a name="Continue"></a>
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<a name="Continue-_0028continue_0029"></a>
<h4 class="subsubsection">4.4.2.5 Continue (‘<samp>continue</samp>’)</h4>
<dl compact="compact">
<dd><a name="index-continue"></a>
<a name="index-c-_0028continue_0029"></a>
</dd>
<dt> <code>continue <span class="roman">[</span><var>- | line-specification</var><span class="roman">]</span></code></dt>
<dt> <code>c <span class="roman">[</span><var>line-specification</var><span class="roman">]</span></code></dt>
<dd><p>Resume program execution, at the address where your script last
stopped; any breakpoints set at that address are bypassed.
</p>
<p>The optional argument <var>line-specification</var> allows you to specify a
location (a line number, function, or filename linenumber combination)
to set a one-time breakpoint which is deleted when that breakpoint is
reached. Should the program stop before that breakpoint is reached, in
a listing of the breakpoints you will see this entry with the
condition 9999 which indicates a one-time breakpoint.
</p>
<p>If instead of a line specification you enter <code>-</code>, debugging will be
turned of after continuing causing the program to run at full speed.
</p></dd>
</dl>
<p>To resume execution at a different place, you can use <code>return</code>
(see section <a href="#Returning">Returning from a function</a>) to go back to the
calling function or sourced script. If you are nested inside a
subshell, <code>quit</code> with a value for the number of subshells to
exit also functions like a return.
</p>
<hr size="6">
<a name="Debug"></a>
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<a name="Debug-_0028debug_0029"></a>
<h4 class="subsubsection">4.4.2.6 Debug (‘<samp>debug</samp>’)</h4>
<dl compact="compact">
<dd><a name="index-debug"></a>
</dd>
<dt> <code>debug <span class="roman">[</span><var>script-name</var><span class="roman">]</span></code></dt>
<dd><p>Debug into <var>script-name</var>. If no name is given the current source line
is used. In either case the options are prepended to cause the
debugger to run.
</p>
<p>The nesting level of the debugger is saved inside environment variable
<code>_Dbg_DEBUGGER_LEVEL</code>. The debugger prompt indicates the level of nesting
by enclosing the history in that many nestings of <code><></code> symbols.
</p>
</dd>
</dl>
<hr size="6">
<a name="Returning"></a>
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<a name="Returning-from-a-function_002c-sourced-file_002c-or-subshell-_0028return_0029"></a>
<h4 class="subsubsection">4.4.2.7 Returning from a function, sourced file, or subshell (‘<samp>return</samp>’)</h4>
<dl compact="compact">
<dd><a name="index-returning-from-a-function_002c-sourced-file-or-subshell"></a>
<a name="index-return"></a>
</dd>
<dt> <code>return</code></dt>
<dd><p>You can cancel execution of a function call or a subshell with the
<code>return</code> command.
</p></dd>
</dl>
<p>The <code>return</code> command does not resume execution; it leaves the
program stopped in the state that would exist if the function had just
returned. See also the <code>quit</code> command (<a href="#Quit">Quitting the BASH debugger</a>). In some situations <code>return</code> is similar to
<code>quit</code>: in particular when the script is <em>not</em> currenlty
inside in a function and the number of subshells in effect is 0, or
when a subshell count of 1 is given on the <code>quit</code> command.
</p>
<p>In contrast, the <code>finish</code> command (see section <a href="#Finish">Finish</a>)
resumes execution until the selected stack frame returns naturally.
</p>
<hr size="6">
<a name="Signals"></a>
<table cellpadding="1" cellspacing="1" border="0">
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</tr></table>
<a name="Signals-_0028handle_002c-info-handle_002c-signal_0029"></a>
<h3 class="subsection">4.4.3 Signals (‘<samp>handle</samp>’, ‘<samp>info handle</samp>’, ‘<samp>signal</samp>’)</h3>
<a name="index-signals"></a>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top"><a href="#handle">4.4.3.1 Intercepting Signals (‘<samp>handle</samp>’, ‘<samp>info handle</samp>’)</a></td><td> </td><td align="left" valign="top"> Specify which signals to handle and show what’s been set
</td></tr>
<tr><td align="left" valign="top"><a href="#signal">4.4.3.2 Sending your program a signal (‘<samp>signal</samp>’)</a></td><td> </td><td align="left" valign="top"> Send a signal to your program
</td></tr>
</table>
<p>A signal is an asynchronous event that can happen in a program. The
operating system defines the possible kinds of signals, and gives each
kind a name and a number. For example, in Unix <code>SIGINT</code> is the
signal a program gets when you type an interrupt character (often
<kbd>C-c</kbd>); <code>SIGALRM</code> occurs when the alarm clock timer goes off
(which happens only if your program has requested an alarm).
</p>
<p>Some signal handlers are installed and changed for the <acronym>BASH</acronym> debugger’s
normal use: <code>SIGDEBUG</code> and <code>SIGEXIT</code>. <code>SIGDEBUG</code> is
used by the debugger to potentially stop your program before execution
of each statement occurs, and <code>SIGEXIT</code> is used to catch your
program just before it is set to leave so you have the option of
restarting the program with the same options (and not leave the
debugger) or let the program quit.
</p>
<p>Signal handlers that the debugged script might have installed are
saved and called before the corresponding debugger handler. Thus, the
debugged program should work roughly in the same fashion as when it is
not debugged. However there are some call-stack variables which
inevitably will differ. To try to hedge this a little so the behaviour
is the same, the <acronym>BASH</acronym> debugger will modify arguments to the traps if it
finds one of the call-stack that change as a result of the debugger
being in place. In particluar <code>$LINENO</code> will get replaced with
<code>${BASH_LINENO[0]}</code>; also <code>${BASH_LINENO[0]}</code> and
<code>${BASH_SOURCE[0]}</code> get replaced with
<code>${BASH_LINENO[1]}</code> and <code>${BASH_SOURCE[1]}</code>
respectively.
</p>
<p>The debugger also installs an interrupt handler <code>SIGINT</code> so that
errant programs can be interrupted and you can find out where the
program was when you interrupted it.
</p>
<a name="index-fatal-signals"></a>
<p>Some signals, including <code>SIGALRM</code>, are a normal part of the
functioning of your program. Others, such as <code>SIGSEGV</code>, indicate
errors; these signals are <em>fatal</em> (they kill your program immediately) if the
program has not specified in advance some other way to handle the signal.
<code>SIGINT</code> does not indicate an error in your program, but it is normally
fatal so it can carry out the purpose of the interrupt: to kill the program.
</p>
<p><acronym>BASH</acronym> has the ability to detect any occurrence of a signal in your
program. You can tell <acronym>BASH</acronym> in advance what to do for each kind of
signal.
</p>
<a name="index-handling-signals"></a>
<p>Normally, <acronym>BASH</acronym> is set up to let the non-erroneous signals like
<code>SIGALRM</code> be silently passed to your program
(so as not to interfere with their role in the program’s functioning)
but to stop your program immediately whenever an error signal happens.
You can change these settings with the <code>handle</code> command.
</p>
<hr size="6">
<a name="handle"></a>
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</tr></table>
<a name="Intercepting-Signals-_0028handle_002c-info-handle_0029"></a>
<h4 class="subsubsection">4.4.3.1 Intercepting Signals (‘<samp>handle</samp>’, ‘<samp>info handle</samp>’)</h4>
<dl compact="compact">
<dd><a name="index-handle"></a>
</dd>
<dt> <code>handle <var>signal</var> <var>keywords</var>…</code></dt>
<dd><p>Change the way <acronym>BASH</acronym> handles signal <var>signal</var>. <var>signal</var>
can be the number of a signal or its name (with or without the
‘<samp>SIG</samp>’ at the beginning). The <var>keywords</var> say what change to make.
<a name="index-info-signals"></a>
</p></dd>
<dt> <code>info signals</code></dt>
<dt> <code>info handle</code></dt>
<dd><p>Print a table of all the kinds of signals and how <acronym>BASH</acronym> has been told to
handle each one. You can use this to see the signal numbers of all
the defined types of signals.
</p>
<p><code>info handle</code> is an alias for <code>info signals</code>.
</p>
</dd>
</dl>
<p>The keywords allowed by the <code>handle</code> command can be abbreviated.
Their full names are:
</p>
<dl compact="compact">
<dt> <code>stop</code></dt>
<dd><p><acronym>BASH</acronym> should stop your program when this signal happens. This implies
the <code>print</code> keyword as well.
</p>
</dd>
<dt> <code>nostop</code></dt>
<dd><p><acronym>BASH</acronym> should not stop your program when this signal happens. It may
still print a message telling you that the signal has come in.
</p>
</dd>
<dt> <code>print</code></dt>
<dd><p><acronym>BASH</acronym> should print a message when this signal happens.
</p>
</dd>
<dt> <code>noprint</code></dt>
<dd><p><acronym>BASH</acronym> should not mention the occurrence of the signal at all.
</p>
</dd>
<dt> <code>stack</code></dt>
<dd><p><acronym>BASH</acronym> should print a stack trace when this signal happens.
</p>
</dd>
<dt> <code>nostack</code></dt>
<dd><p><acronym>BASH</acronym> should not print a stack trace when this signal occurs.
</p>
</dd>
</dl>
<hr size="6">
<a name="signal"></a>
<table cellpadding="1" cellspacing="1" border="0">
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</tr></table>
<a name="Sending-your-program-a-signal-_0028signal_0029"></a>
<h4 class="subsubsection">4.4.3.2 Sending your program a signal (‘<samp>signal</samp>’)</h4>
<dl compact="compact">
<dd><a name="index-signal"></a>
</dd>
<dt> <code>signal <span class="roman"><var>signal-name</var> | <var>signal-number</var></span></code></dt>
<dd><p>You can use the <code>signal</code> command send a signal to your
program. Supply either the signal name, e.g. <code>SIGINT</code>, or the
signal number <code>15</code>.
</p></dd>
</dl>
<hr size="6">
<a name="Program-Information"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#signal" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#Info" title="Next section in reading order"> > </a>]</td>
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</tr></table>
<a name="Status-and-Debugger-Settings-_0028info_002c-show_0029"></a>
<h2 class="section">4.5 Status and Debugger Settings (‘<samp>info</samp>’, ‘<samp>show</samp>’)</h2>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top"><a href="#Info">4.5.1 Showing information about the program being debugged (‘<samp>info</samp>’)</a></td><td> </td><td align="left" valign="top"> Showing information about the program being debugged
</td></tr>
<tr><td align="left" valign="top"><a href="#Show">4.5.2 Show information about the debugger (‘<samp>show</samp>’)</a></td><td> </td><td align="left" valign="top"> Show information about the debugger
</td></tr>
</table>
<p>In addition to <code>help</code>, you can use the <acronym>BASH</acronym> commands <code>info</code>
and <code>show</code> to inquire about the state of your program, or the
state of <acronym>BASH</acronym> itself. Each command supports many topics of inquiry;
here we introduce each of them in the appropriate context. The
listings under <code>info</code> and under <code>show</code> in the Index point to
all the sub-commands. See section <a href="#Command-Index">Command Index</a>.
</p>
<hr size="6">
<a name="Info"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Program-Information" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#Show" title="Next section in reading order"> > </a>]</td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Debugger-Command-Reference" title="Beginning of this chapter or previous chapter"> << </a>]</td>
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<td valign="middle" align="left">[<a href="#Top" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Showing-information-about-the-program-being-debugged-_0028info_0029"></a>
<h3 class="subsection">4.5.1 Showing information about the program being debugged (‘<samp>info</samp>’)</h3>
<p>This <code>info</code> command (abbreviated <code>i</code>) is for describing the state of
your program. For example, you can list the current <code>$1</code>, <code>$2</code>
parameters with <code>info args</code>, or list the breakpoints you have set
with <code>info breakpoints</code> or <code>info watchpoints</code>. You can get
a complete list of the <code>info</code> sub-commands with <code>help
info</code>.
</p>
<dl compact="compact">
<dd><a name="index-info-args"></a>
</dd>
<dt> <code>info args</code></dt>
<dd><p>Argument variables (e.g. $1, $2, ...) of the current stack frame.
<a name="index-info-breakpoints-1"></a>
</p></dd>
<dt> <code>info breakpoints</code></dt>
<dd><p>Status of user-settable breakpoints
<a name="index-info-display"></a>
</p></dd>
<dt> <code>info display</code></dt>
<dd><p>Show all display expressions
<a name="index-info-files"></a>
</p></dd>
<dt> <code>info files</code></dt>
<dd><p>Source files in the program
<a name="index-info-functions"></a>
</p></dd>
<dt> <code>info functions</code></dt>
<dd><p>All function names
<a name="index-info-line"></a>
</p></dd>
<dt> <code>info line</code></dt>
<dd><p>list current line number and and file name
<a name="index-info-program"></a>
</p></dd>
<dt> <code>info program</code></dt>
<dd><p>Execution status of the program.
<a name="index-info-signals-1"></a>
</p></dd>
<dt> <code>info signals</code></dt>
<dd><p>What debugger does when program gets various signals
<a name="index-info-source"></a>
</p></dd>
<dt> <code>info source</code></dt>
<dd><p>Information about the current source file
<a name="index-info-stack"></a>
</p></dd>
<dt> <code>info stack</code></dt>
<dd><p>Backtrace of the stack
<a name="index-info-terminal-1"></a>
</p></dd>
<dt> <code>info terminal</code></dt>
<dd><p>Print terminal device
<a name="index-info-variables"></a>
</p></dd>
<dt> <code>info variables</code></dt>
<dd><p>All global and static variable names
</p></dd>
</dl>
<hr size="6">
<a name="Show"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Info" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#Stack" title="Next section in reading order"> > </a>]</td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Debugger-Command-Reference" title="Beginning of this chapter or previous chapter"> << </a>]</td>
<td valign="middle" align="left">[<a href="#Program-Information" title="Up section"> Up </a>]</td>
<td valign="middle" align="left">[<a href="#Front-Ends" title="Next chapter"> >> </a>]</td>
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<td valign="middle" align="left">[<a href="#Function-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Show-information-about-the-debugger-_0028show_0029"></a>
<h3 class="subsection">4.5.2 Show information about the debugger (‘<samp>show</samp>’)</h3>
<p>In contrast to <code>info</code>, <code>show</code> is for describing the state of
<acronym>BASH</acronym> itself. You can change most of the things you can
<code>show</code>, by using the related command <code>set</code>;
</p>
<p>The distinction between <code>info</code> and <code>show</code> however is a bit
fuzzy and is kept here to try to follow the GDB interface.
For example, to list the arguments given to your script use
<code>show args</code>; <code>info args</code> does something different.
</p>
<p>Here are three miscellaneous <code>show</code> subcommands, all of which are
exceptional in lacking corresponding <code>set</code> commands:
</p>
<dl compact="compact">
<dd><a name="index-show-version"></a>
<a name="index-version-number"></a>
</dd>
<dt> <code>show version</code></dt>
<dd><p>Show what version of <acronym>BASH</acronym> is running. You should include this
information in <acronym>BASH</acronym> bug-reports. If multiple versions of
<acronym>BASH</acronym> are in use at your site, you may need to determine which
version of <acronym>BASH</acronym> you are running; as <acronym>BASH</acronym> evolves, new
commands are introduced, and old ones may wither away. Also, many
system vendors ship variant versions of <acronym>BASH</acronym>, and there are
variant versions of <acronym>BASH</acronym> in <small>GNU</small>/Linux distributions as well.
The version number is the same as the one announced when you start
<acronym>BASH</acronym>.
</p>
<a name="index-show-copying"></a>
</dd>
<dt> <code>show copying</code></dt>
<dd><p>Display information about permission for copying <acronym>BASH</acronym>.
</p>
</dd>
<dt> <code>show linetrace</code></dt>
<dd>
<p>Show if line tracing is enabled. See also <a href="#Line-Tracing">Show position information as statements are executed (‘<samp>set linetrace</samp>’)</a>.
</p>
</dd>
<dt> <code>show logging</code></dt>
<dd>
<p>Show summary information of logging variables which can be set via
<code>set logging</code>. See also <a href="#Logging">Logging output (‘<samp>set logging</samp>’, ‘<samp>set logging file</samp>’...)</a>.
</p>
</dd>
<dt> <code>show logging file</code></dt>
<dd>
<p>Show the current logging file.
</p>
</dd>
<dt> <code>show logging overwrite</code></dt>
<dd>
<p>Show whether logging overwrites or appends to the log file.
</p>
<a name="index-show-warranty"></a>
</dd>
<dt> <code>show warranty</code></dt>
<dd><p>Display the <small>GNU</small> “NO WARRANTY” statement, or a warranty,
if your version of the <acronym>BASH</acronym> debugger comes with one.
</p>
</dd>
</dl>
<hr size="6">
<a name="Stack"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Show" title="Previous section in reading order"> < </a>]</td>
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Examining-the-Stack-Frame-_0028where_002c-frame_002c-up_002c-down_0029"></a>
<h2 class="section">4.6 Examining the Stack Frame (‘<samp>where</samp>’, ‘<samp>frame</samp>’, ‘<samp>up</samp>’, ‘<samp>down</samp>’)</h2>
<p>When your script has stopped, one thing you’ll probably want to know
is where it stopped and some idea of how it got there.
</p>
<a name="index-call-stack"></a>
<p>Each time your script performs a function call (either as part of a
command substitution or not), or ‘source’s a file, information about
this action is saved. The call stack then is this a history of the
calls that got you to the point that you are currently stopped at.
</p>
<a name="index-selected-frame"></a>
<p>One of the stack frames is <em>selected</em> by the <acronym>BASH</acronym> debugger and many
the <acronym>BASH</acronym> debugger commands refer implicitly to the selected frame. In
particular, whenever you ask the <acronym>BASH</acronym> debugger to list lines without giving
a line number or location the value is found in the selected frame.
There are special the <acronym>BASH</acronym> debugger commands to select whichever frame you
are interested in. See section <a href="#Selection">Selecting a frame</a>.
</p>
<p>When your program stops, <acronym>BASH</acronym> automatically selects the
currently executing frame and describes it briefly, similar to the
<code>frame</code> command.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top"><a href="#Frames">4.6.1 Stack frames</a></td><td> </td><td align="left" valign="top"></td></tr>
<tr><td align="left" valign="top"><a href="#Backtrace">4.6.2 Backtraces (‘<samp>where</samp>’)</a></td><td> </td><td align="left" valign="top"> Backtraces (where)
</td></tr>
<tr><td align="left" valign="top"><a href="#Selection">4.6.3 Selecting a frame (‘<samp>up</samp>’, ‘<samp>down</samp>’, ‘<samp>frame</samp>’)</a></td><td> </td><td align="left" valign="top"> Selecting a frame (up, down, frame)
</td></tr>
<tr><th colspan="3" align="left" valign="top"><pre class="menu-comment">
</pre></th></tr></table>
<hr size="6">
<a name="Frames"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Stack" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#Backtrace" title="Next section in reading order"> > </a>]</td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Debugger-Command-Reference" title="Beginning of this chapter or previous chapter"> << </a>]</td>
<td valign="middle" align="left">[<a href="#Stack" title="Up section"> Up </a>]</td>
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<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Top" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Function-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Stack-frames"></a>
<h3 class="subsection">4.6.1 Stack frames</h3>
<a name="index-frame_002c-definition"></a>
<a name="index-stack-frame"></a>
<p>The call stack is divided up into contiguous pieces called <em>stack
frames</em>, or <em>frames</em> for short; each frame is the data associated
with one call to one function. The frame contains the line number of
the caller of the function, the source-file name that the line refers
to a function name (which could be the built-in name “source”)..
</p>
<a name="index-initial-frame"></a>
<a name="index-outermost-frame"></a>
<a name="index-innermost-frame"></a>
<p>When your script is started, the stack has only one frame, that of the
function <code>main</code>. This is called the <em>initial</em> frame or the
<em>outermost</em> frame. Each time a function is called, a new frame is
made. Each time a function returns, the frame for that function invocation
is eliminated. If a function is recursive, there can be many frames for
the same function. The frame for the function in which execution is
actually occurring is called the <em>innermost</em> frame. This is the most
recently created of all the stack frames that still exist.
</p>
<a name="index-frame-number"></a>
<p>the <acronym>BASH</acronym> debugger assigns numbers to all existing stack frames, starting with
zero for the innermost frame, one for the frame that called it,
and so on upward. These numbers do not really exist in your script;
they are assigned by the <acronym>BASH</acronym> debugger to give you a way of designating stack
frames in the <acronym>BASH</acronym> debugger commands.
</p>
<hr size="6">
<a name="Backtrace"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Frames" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#Selection" title="Next section in reading order"> > </a>]</td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Debugger-Command-Reference" title="Beginning of this chapter or previous chapter"> << </a>]</td>
<td valign="middle" align="left">[<a href="#Stack" title="Up section"> Up </a>]</td>
<td valign="middle" align="left">[<a href="#Front-Ends" title="Next chapter"> >> </a>]</td>
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<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Top" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Function-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Backtraces-_0028where_0029"></a>
<h3 class="subsection">4.6.2 Backtraces (‘<samp>where</samp>’)</h3>
<a name="index-backtraces"></a>
<a name="index-tracebacks"></a>
<a name="index-stack-traces"></a>
<p>A backtrace is essentially the same as the call stack: a summary of
how your script got where it is. It shows one line per frame, for
many frames, starting with the place that you sare stopped at (frame
zero), followed by its caller (frame one), and on up the stack.
</p>
<dl compact="compact">
<dd><a name="index-backtrace"></a>
<a name="index-bt-_0028backtrace_0029"></a>
</dd>
<dt> <code>backtrace</code></dt>
<dt> <code>bt</code></dt>
<dt> <code>where</code></dt>
<dt> <code>T</code></dt>
<dd><p>Print a backtrace of the entire stack: one line per frame for all
frames in the stack.
</p>
</dd>
<dt> <code>backtrace <var>n</var></code></dt>
<dt> <code>bt <var>n</var></code></dt>
<dt> <code>where <var>n</var></code></dt>
<dt> <code>T <var>n</var></code></dt>
<dd><p>Similar, but print only the innermost <var>n</var> frames.
</p>
</dd>
</dl>
<a name="index-where"></a>
<p>The names <code>where</code> and <code>T</code> are additional aliases for
<code>backtrace</code>.
</p>
<p>Each line in the backtrace shows the frame number and the function
name, the source file name and line number, as well as the function name.
</p>
<p>Here is an example of a backtrace taken a program in the
regression-tests ‘<tt>parm.sh</tt>’.
</p>
<table><tr><td> </td><td><pre class="smallexample">% ../bashdb -n -L .. parm.sh
Bourne-Again Shell Debugger, release 4.0-0.4
Copyright 2002, 2003, 2004, 2006, 2007, 2008, 2009 Rocky Bernstein
This is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
(./parm.sh:21):
21: fn1 5
bashdb<0> <b>continue fn3</b>
One-time breakpoint 1 set in file ./parm.sh, line 17.
fn2: testing 1 2 3
(./parm.sh:17):
17: fn3() {
bashdb<1> <b>where</b>
->0 in file `./parm.sh' at line 14
##1 fn3() called from file `./parm.sh' at line 14
##2 fn2("testing 1", "2 3") called from file `parm.sh' at line 5
##3 fn1("0") called from file `parm.sh' at line 9
##4 fn1("1") called from file `parm.sh' at line 9
##5 fn1("2") called from file `parm.sh' at line 9
##6 fn1("3") called from file `parm.sh' at line 9
##7 fn1("4") called from file `parm.sh' at line 9
##8 fn1("5") called from file `parm.sh' at line 21
##9 source("parm.sh") called from file `bashdb' at line 143
##10 main("-n", "-L", "..", "parm.sh") called from file `bashdb' at line 0
</pre></td></tr></table>
<p>The display for “frame” zero isn’t a frame at all, although it has
the same information minus a function name; it just indicates that
your script has stopped at the code for line <code>14</code>
of <code>./parm.sh</code>.
</p>
<hr size="6">
<a name="Selection"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Backtrace" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#List" title="Next section in reading order"> > </a>]</td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Debugger-Command-Reference" title="Beginning of this chapter or previous chapter"> << </a>]</td>
<td valign="middle" align="left">[<a href="#Stack" title="Up section"> Up </a>]</td>
<td valign="middle" align="left">[<a href="#Front-Ends" title="Next chapter"> >> </a>]</td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Top" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Function-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Selecting-a-frame-_0028up_002c-down_002c-frame_0029"></a>
<h3 class="subsection">4.6.3 Selecting a frame (‘<samp>up</samp>’, ‘<samp>down</samp>’, ‘<samp>frame</samp>’)</h3>
<p>Commands for listing source code in your script work on whichever
stack frame is selected at the moment. Here are the commands for
selecting a stack frame; all of them finish by printing a brief
description of the stack frame just selected.
</p>
<dl compact="compact">
<dd><a name="index-up-_005bn_005d"></a>
</dd>
<dt> <code>up <span class="roman">[</span><var>n</var><span class="roman">]</span></code></dt>
<dd><p>Move <var>n</var> frames up the stack. For positive numbers <var>n</var>, this
advances toward the outermost frame, to higher frame numbers, to
frames that have existed longer. Using a negative <var>n</var> is the same
as issuing a <code>down</code> command of the absolute value of the <var>n</var>.
Using zero for <var>n</var> does no frame adjustment, but since the current
position is redisplayed, it may trigger a resyncronization if there is
a front end also watching over things.
</p>
<p><var>n</var> defaults to one. You may appreviate <code>up</code> as <code>u</code>.
</p>
<a name="index-down"></a>
<a name="index-do-_0028down_0029"></a>
</dd>
<dt> <code>down <span class="roman">[</span><var>n</var><span class="roman">]</span></code></dt>
<dd><p>Move <var>n</var> frames down the stack. For positive numbers <var>n</var>, this
advances toward the innermost frame, to lower frame numbers, to frames
that were created more recently. Using a negative <var>n</var> is the same
as issuing a <code>up</code> command of the absolute value of the <var>n</var>.
Using zero for <var>n</var> does no frame adjustment, but since the current
position is redisplayed, it may trigger a resyncronization if there is
a front end also watching over things.
</p>
<p><var>n</var> defaults to one. You may abbreviate <code>down</code> as <code>do</code>.
</p></dd>
</dl>
<p>All of these commands end by printing two lines of output describing the
frame. The first line shows the frame number, the function name, the
arguments, and the source file and line number of execution in that
frame. The second line shows the text of that source line.
</p>
<p>For example:
</p>
<table><tr><td> </td><td><pre class="smallexample">bashdb<8> <b>up</b>
19: sourced_fn
bashdb<8> <b>T</b>
##0 in file `./bashtest-sourced' at line 8
->1 sourced_fn() called from file `bashtest-sourced' at line 19
##2 source() called from file `bashdb-test1' at line 23
##3 fn2() called from file `bashdb-test1' at line 33
##4 fn1() called from file `bashdb-test1' at line 42
##5 main() called from file `bashdb-test1' at line 0
</pre></td></tr></table>
<p>After such a printout, the <code>list</code> command with no arguments
prints ten lines centered on the point of execution in the frame.
See section <a href="#List">Printing source lines</a>.
</p>
<dl compact="compact">
<dd><a name="index-frame"></a>
<a name="index-current-stack-frame"></a>
</dd>
<dt> <code>frame <var>args</var></code></dt>
<dd><p>The <code>frame</code> command allows you to move from one stack frame to
another, and to print the stack frame you select. <var>args</var> is the
the stack frame number; <code>frame 0</code> then will always show the
current and most recent stack frame.
</p>
<p>If a negative number is given, counting is from the other end of the
stack frame, so <code>frame -1</code> shows the least-recent, outermost or
most “main” stack frame.
</p>
<p>Without an argument, <code>frame</code> prints the current stack
frame. Since the current position is redisplayed, it may trigger a
resyncronization if there is a front end also watching over
things.
</p></dd>
</dl>
<hr size="6">
<a name="List"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Selection" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#Edit" title="Next section in reading order"> > </a>]</td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Debugger-Command-Reference" title="Beginning of this chapter or previous chapter"> << </a>]</td>
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<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Top" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Function-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Examining-Source-Files-_0028list_0029"></a>
<h2 class="section">4.7 Examining Source Files (‘<samp>list</samp>’)</h2>
<p>the <acronym>BASH</acronym> debugger can print parts of your script’s source. When your
script stops, the <acronym>BASH</acronym> debugger spontaneously prints the line where it
stopped. Likewise, when you select a stack frame (see section <a href="#Selection">Selecting a frame</a>), the <acronym>BASH</acronym> debugger prints the line where execution in
that frame has stopped. You can print other portions of source files
by explicit command.
</p>
<p>If you use the <acronym>BASH</acronym> debugger through its <small>GNU</small> Emacs interface, you may
prefer to use Emacs facilities to view source; see <a href="#Emacs">Using the <acronym>BASH</acronym> debugger under <small>GNU</small> Emacs</a>.
</p>
<a name="index-list"></a>
<a name="index-l-_0028list_0029"></a>
<p>To print lines from a source file, use the <code>list</code> command
(abbreviated <code>l</code>). By default, ten lines are printed.
There are several ways to specify what part of the file you want to print.
</p>
<p>Here are the forms of the <code>list</code> command most commonly used:
</p>
<dl compact="compact">
<dt> <code>list <var>linenum</var></code></dt>
<dt> <code>l <var>linenum</var></code></dt>
<dd><p>Print lines centered around line number <var>linenum</var> in the
current source file.
</p>
</dd>
<dt> <code>list <var>function</var></code></dt>
<dt> <code>l <var>function</var></code></dt>
<dd><p>Print the text of <var>function</var>.
</p>
</dd>
<dt> <code>list</code></dt>
<dt> <code>l</code></dt>
<dd><p>Print more lines. If the last lines printed were printed with a
<code>list</code> command, this prints lines following the last lines
printed; however, if the last line printed was a solitary line printed
as part of displaying a stack frame (see section <a href="#Stack">Examining the Stack</a>), this prints lines centered around that line.
</p>
</dd>
<dt> <code>list -</code></dt>
<dt> <code>l -</code></dt>
<dd><p>Print lines just before the lines last printed.
</p></dd>
</dl>
<p>By default, the <acronym>BASH</acronym> debugger prints ten source lines with any of these forms of
the <code>list</code> command.
You can change this using <code>set listsize</code>:
</p>
<dl compact="compact">
<dd><a name="index-set-listsize"></a>
</dd>
<dt> <code>set listsize <var>count</var></code></dt>
<dd><p>Make the <code>list</code> command display <var>count</var> source lines (unless
the <code>list</code> argument explicitly specifies some other number).
</p>
<a name="index-show-listsize"></a>
</dd>
<dt> <code>show listsize</code></dt>
<dd><p>Display the number of lines that <code>list</code> prints.
</p>
</dd>
</dl>
<p>Repeating a <code>list</code> command with <RET> discards the argument,
so it is equivalent to typing just <code>list</code>. This is more useful
than listing the same lines again. An exception is made for an
argument of ‘<samp>-</samp>’; that argument is preserved in repetition so that
each repetition moves up in the source file.
</p>
<a name="index-linespec"></a>
<p>In general, the <code>list</code> command expects you to supply a
<em>linespecs</em>. Linespecs specify source lines; there are several ways
of writing them, but the effect is always to specify some source line.
</p>
<p>Here is a complete description of the possible arguments for <code>list</code>:
</p>
<dl compact="compact">
<dt> <code>list <var>linespec</var></code></dt>
<dd><p>Print lines centered around the line specified by <var>linespec</var>.
</p>
</dd>
<dt> <code>list <var>first</var> <var>increment</var></code></dt>
<dd><p>Print <var>increment</var> lines starting from <var>first</var>
</p>
</dd>
<dt> <code>list <var>first</var></code></dt>
<dd><p>Print lines starting with <var>first</var>.
</p>
</dd>
<dt> <code>list -</code></dt>
<dd><p>Print lines just before the lines last printed.
</p>
</dd>
<dt> <code>list .</code></dt>
<dd><p>Print lines after where the script is stopped.
</p>
</dd>
<dt> <code>list</code></dt>
<dd><p>As described in the preceding table.
</p></dd>
</dl>
<p>Here are the ways of specifying a single source line—all the
kinds of linespec.
</p>
<dl compact="compact">
<dt> <code><var>number</var></code></dt>
<dd><p>Specifies line <var>number</var> of the current source file.
When a <code>list</code> command has two linespecs, this refers to
the same source file as the first linespec.
</p>
</dd>
<dt> <code><var>filename</var>:<var>number</var></code></dt>
<dd><p>Specifies line <var>number</var> in the source file <var>filename</var>.
</p>
</dd>
<dt> <code><var>function</var></code></dt>
<dd><p>Specifies the line that function <var>function</var> is listed on.
</p>
</dd>
</dl>
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<a name="Editing-Source-files-_0028edit_0029"></a>
<h2 class="section">4.8 Editing Source files (‘<samp>edit</samp>’)</h2>
<p>To edit the lines in a source file, use the <code>edit</code> command. The
editing program of your choice is invoked with the current line set to
the active line in the program. Alternatively, you can give a line
specification to specify what part of the file you want to print if
you want to see other parts of the program.
</p>
<p>You can customize to use any editor you want by using the
<code>EDITOR</code> environment variable. The only restriction is that your
editor (say <code>ex</code>), recognizes the following command-line syntax:
</p><table><tr><td> </td><td><pre class="smallexample">ex +<var>number</var> file
</pre></td></tr></table>
<p>The optional numeric value +<var>number</var> specifies the number of the
line in the file where to start editing. For example, to configure
the <acronym>BASH</acronym> debugger to use the <code>vi</code> editor, you could use these commands
with the <code>sh</code> shell:
</p><table><tr><td> </td><td><pre class="smallexample">EDITOR=/usr/bin/vi
export EDITOR
gdb …
</pre></td></tr></table>
<p>or in the <code>csh</code> shell,
</p><table><tr><td> </td><td><pre class="smallexample">setenv EDITOR /usr/bin/vi
gdb …
</pre></td></tr></table>
<dl compact="compact">
<dd><a name="index-edit-_005bline_002dspecification_005d"></a>
</dd>
<dt> <code>edit <span class="roman">[</span><var>line specification</var><span class="roman">]</span></code></dt>
<dd><p>Edit line specification using the editor specified by the
<code>EDITOR</code> environment variable.
</p></dd>
</dl>
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<a name="Searching-source-files-_0028search_002c-reverse_002c-_002f_002e_002e_002e_002f_002c-_003f_002e_002e_003f_0029"></a>
<h2 class="section">4.9 Searching source files (‘<samp>search</samp>’, ‘<samp>reverse</samp>’, ‘<samp>/.../</samp>’, ‘<samp>?..?</samp>’)</h2>
<a name="index-searching"></a>
<a name="index-reverse_002dsearch"></a>
<p>There are two commands for searching through the current source file
for a <acronym>BASH</acronym> extended pattern-matching expression.
</p>
<dl compact="compact">
<dd><a name="index-search"></a>
<a name="index-forward"></a>
</dd>
<dt> <code>forward <var>bash-pattern</var></code></dt>
<dt> <code>search <var>bash-pattern</var></code></dt>
<dd><p>The command ‘<samp>forward <var>bash-pattern</var></samp>’ checks each line,
starting with the one following the current line, for a match for
<var>bash-pattern</var> which is an extended bash pattern-matching
expression. It lists the line that is found. You can use the synonym
‘<samp>search <var>bash-pattern</var></samp>’ or abbreviate the command name as
<code>fo</code> or <code>/<var>pat</var>/</code>.
</p>
</dd>
<dt> <code>reverse <var>bash-pattern</var></code></dt>
<dd><p>The command ‘<samp>reverse <var>bash-pattern</var></samp>’ checks each line, starting
with the one before the last line listed and going backward, for a match
for <var>bash-pattern</var>. It lists the line that is found. You can abbreviate
this command as <code>rev</code> or <code>?<var>bash-pattern</var>?</code>.
</p></dd>
</dl>
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<a name="Examining-Data-_0028print_002c-examine_002c-info-variables_0029"></a>
<h2 class="section">4.10 Examining Data (‘<samp>print</samp>’, ‘<samp>examine</samp>’, ‘<samp>info variables</samp>’)</h2>
<a name="index-printing-data"></a>
<a name="index-examining-data"></a>
<a name="index-print"></a>
<p>One way to examine string data in your script is with the <code>print</code>
command (abbreviated <code>p</code>). However a more versatile print command
is <code>x</code>; it can print variable and function definitions and can do
arithmetic computations. Finally, the most general method would be
via <code>eval echo</code>.
</p>
<dl compact="compact">
<dd><a name="index-print-1"></a>
<a name="index-p-_0028print_0029"></a>
</dd>
<dt> <code>print <var>expr</var></code></dt>
<dd>
<p>Use <code>print</code> to display strings as you would from <code>echo</code>. And
as such, variable names to be substituted have to be preceded with a
dollar sign. As with echo, filename expansion, e.g. tilde expansion,
is performed on unquoted strings. So for example if you want to print
a *, you would write ‘<samp>print "*"</samp>’, not ‘<samp>print *</samp>’. If you want
to have the special characters dollars sign appear, use a backslash.
</p>
<table><tr><td> </td><td><pre class="smallexample">bashdb<0> <b>print the value of x is $x</b>
the value of x is 22
bashdb<1> <b>p The home directory for root is ~root</b>
The home directory for root is /root
bashdb<2> <b>p '*** You may have won $$$ ***'</b>
*** You may have won $$$ ***
bashdb<3> # Note the use of the single quotes.
bashdb<3> # Compare what happens with double quotes or no quotes
</pre></td></tr></table>
</dd>
<dt> <code>print</code></dt>
<dt> <code>p</code></dt>
<dd><p>If you omit <var>expr</var>, the <acronym>BASH</acronym> debugger displays the last expression again.
</p>
</dd>
<dt> <code>x <var>variable1</var> <span class="roman">[</span><var>variable2...</var><span class="roman">]</span></code></dt>
<dt> <code>x <var>expr</var></code></dt>
<dd><a name="index-x-_0028examine_0029"></a>
<a name="index-examine"></a>
<p>This is a smarter, more versatile “print” command, and although sometimes
it might not be what you want, and you may want to resort to either
<code>print</code> or <code>eval echo...</code>.
</p>
<p>As with <code>print</code>, if you omit <var>expr</var>, the <acronym>BASH</acronym> debugger displays
the last expression again.
</p>
<p>The <code>x</code> command first checks if <var>expr</var> is variable or a list
of variables delimited by spaces. If it is, the definition(s) and
value(s) of each printed via <acronym>BASH</acronym>’s <code>declare -p</code>
command. This will show the variable’s attributes such as if it is
read only or if it is an integer. If the variable is an array, that is
show and the array values are printed.
</p>
<p>If instead <var>expr</var> is a function, the function definition is
printed via <acronym>BASH</acronym>’s <code>declare -f</code> command. If <var>expr</var>
was neither a variable nor an expression, then we try to get a value
via <code>let</code>. And if this returns an error, as a last resort we call
<code>print</code> and give what it outputs.
</p>
<p>Since <code>let</code> may be used internally and since (to my thinking)
<code>let</code> does funny things, the results may seem odd unless you
understand the sequence tried above and how <code>let</code> works. For
“example if the variable <code>foo</code> has value 5, then ‘<samp>x foo</samp>’
shows the definition of foo with value 5, and ‘<samp>x foo+5</samp>’ prints 10
as expected. So far so good. However if <code>foo</code> is has the value
‘<samp>alpha</samp>’, ‘<samp>x foo+5</samp>’ prints 5 because <code>let</code> has converted
the string ‘<samp>alpha</samp>’ into the numeric value 0. So ‘<samp>p foo+5</samp>’ will
simply print “foo+5”; if you want the value of “foo” substituted
inside a string, for example you expect “the value of foo is $foo”
to come out “the value of foo is 5”, then the right command to use
is <code>print</code> rather than <code>x</code>, making sure you add the dollar
onto the beginning of the variable.
</p>
<table><tr><td> </td><td><pre class="smallexample">bashdb<0> <b>examine x y</b>
declare -- x="22"
declare -- y="23"
bashdb<1> <b>examine x+y</b>
45
bashdb<2> <b>x fn1</b>
fn1 ()
{
echo "fn1 here";
x=5;
fn3
}
bashdb<2> <b>x FUNCNAME</b>
declare -a FUNCNAME='([0]="_Dbg_cmd_x" [1]="_Dbg_cmdloop" [2]="_Dbg_debug_trap_handler" [3]="main")'
</pre></td></tr></table>
</dd>
<dt> <code>V <span class="roman">[</span><var>!</var><span class="roman">]</span><span class="roman">[</span><var>pattern</var><span class="roman">]</span></code></dt>
<dd><a name="index-V-_0028info-variables_0029"></a>
<a name="index-info-variables-1"></a>
<p>If you want to all list variables and values or a set of
variables by pattern, use this command.
</p>
<table><tr><td> </td><td><pre class="smallexample">bashdb<0> <b>V dq*</b>
dq_args="dq_*"
dq_cmd="V"
bashdb<1> <b>V FUNCNAME</b>
FUNCNAME='([0]="_Dbg_cmd_list_variables" [1]="_Dbg_cmdloop" [2]="_Dbg_debug_trap_handler" [3]="main")'
</pre></td></tr></table>
</dd>
</dl>
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<a name="Running-Arbitrary-BASH-and-Shell-commands-_0028eval_002c-shell_0029"></a>
<h2 class="section">4.11 Running Arbitrary BASH and Shell commands (‘<samp>eval</samp>’, ‘<samp>shell</samp>’)</h2>
<p>The two most general commands and most “low-level” are <code>eval</code>
and <code>shell</code>.
</p>
<dl compact="compact">
<dt> <code>eval</code></dt>
<dt> <code>e</code></dt>
<dd><a name="index-e-_0028eval_0029"></a>
<a name="index-eval"></a>
<p>In contrast to the commands of the last section the most general way
to examine data is through <code>eval</code>. But you do much more with
this; you can change the values of variables, since, you are just
evaluating <acronym>BASH</acronym> code.
</p>
<p>If you expect output, you should arrange that in the command, such as
via <code>echo</code> or <code>printf</code>. For example, to print the value of
<var>foo</var>, you would type ‘<samp>e echo $foo</samp>’. This is bit longer than
‘<samp>p $foo</samp>’ or (when possible) ‘<samp>x foo</samp>’. However suppose you
wanted to find out how the builtin test operator ‘<samp>[</samp>’ works with
the ‘<samp>-z</samp>’ test condition. You could use <code>eval</code> to do this
such as ‘<samp>e [ -z "$foo"] && echo "yes"</samp>’.
</p>
<a name="index-shell"></a>
<a name="index-_0021_0021-_0028shell_0029"></a>
<a name="index-shell-escape"></a>
</dd>
<dt> <code>shell <var>command string</var></code></dt>
<dt> <code>!!</code></dt>
<dd>
<p>If you need to execute occasional shell commands during your
debugging session, there is no need to leave or suspend the <acronym>BASH</acronym> debugger; you can
just use the <code>shell</code> command or its alias <code>!!</code>.
</p>
<p>Invoke a shell to execute <var>command string</var>.
</p>
</dd>
</dl>
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<a name="Interfacing-to-the-OS-_0028cd_002c-pwd_0029"></a>
<h2 class="section">4.12 Interfacing to the OS (‘<samp>cd</samp>’, ‘<samp>pwd</samp>’)</h2>
<dl compact="compact">
<dd><a name="index-cd-_005bdirectory_005d"></a>
<a name="index-change-working-directory"></a>
</dd>
<dt> <code>cd</code></dt>
<dd>
<p>Set working directory to <var>directory</var> for debugger and program
being debugged. Tilde expansion, variable and filename expansion is
performed on <var>directory</var>. If no directory is given, we print out the
current directory which is really the same things as running
<code>pwd</code>.
</p>
<p>Note that <code>gdb</code> is a little different in that it peforms tilde expansion
but not filename or variable expansion and the directory argument is
not optional as it is here.
</p>
<a name="index-pwd"></a>
<a name="index-print-working-directory"></a>
</dd>
<dt> <code>pwd</code></dt>
<dd>
<p>Prints the working directory as the program sees things.
</p>
</dd>
</dl>
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<a name="Automatic-display-_0028display_002c-undisplay_0029"></a>
<h2 class="section">4.13 Automatic display (‘<samp>display</samp>’, ‘<samp>undisplay</samp>’)</h2>
<a name="index-automatic-display"></a>
<a name="index-display-of-expressions"></a>
<p>If you find that you want to print the value of an expression
frequently (to see how it changes), you might want to add it to the
<em>automatic display list</em> so that the <acronym>BASH</acronym> debugger evaluates a
statement each time your program stops. Each expression added to the
list is given a number to identify it; to remove an expression from
the list, you specify that number. The automatic display looks like
this:
</p>
<table><tr><td> </td><td><pre class="example">2 (echo $x): 38
</pre></td></tr></table>
<p>This display shows item numbers, expressions and their current values.
</p>
<dl compact="compact">
<dd><a name="index-display"></a>
</dd>
<dt> <code>display <var>expr</var></code></dt>
<dd><p>Add the expression <var>expr</var> to the list of expressions to display
each time your program stops.
</p>
</dd>
<dt> <code>display</code></dt>
<dd><p>Display the current values of the expressions on the list, just as is
done when your program stops.
</p>
<a name="index-delete-display"></a>
<a name="index-undisplay-dnums_2026"></a>
</dd>
<dt> <code>undisplay <var>dnums</var>…</code></dt>
<dt> <code>delete display <var>dnums</var>…</code></dt>
<dd><p>Remove item numbers <var>dnums</var> from the list of expressions to display.
</p>
<p><code>undisplay</code> does not repeat if you press <RET> after using it.
(Otherwise you would just get the error ‘<samp>No display number …</samp>’.)
</p>
<a name="index-disable-display"></a>
</dd>
<dt> <code>disable display <var>dnums</var>…</code></dt>
<dd><p>Disable the display of item numbers <var>dnums</var>. A disabled display
item is not printed automatically, but is not forgotten. It may be
enabled again later.
</p>
<a name="index-enable-display"></a>
</dd>
<dt> <code>enable display <var>dnums</var>…</code></dt>
<dd><p>Enable display of item numbers <var>dnums</var>. It becomes effective once
again in auto display of its expression, until you specify otherwise.
</p>
<a name="index-info-display-1"></a>
</dd>
<dt> <code>info display</code></dt>
<dd><p>Print the list of expressions previously set up to display
automatically, each one with its item number, but without showing the
values. This includes disabled expressions, which are marked as such.
It also includes expressions which would not be displayed right now
because they refer to automatic variables not currently available.
</p></dd>
</dl>
<hr size="6">
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</tr></table>
<a name="Controlling-bashdb-_0028set_002c-file_002c-prompt_002c-history_002e_002e_002e_0029"></a>
<h2 class="section">4.14 Controlling bashdb (‘<samp>set</samp>’, ‘<samp>file</samp>’, ‘<samp>prompt</samp>’, ‘<samp>history</samp>’...)</h2>
<p>You can alter the way <acronym>BASH</acronym>
interacts with you in various ways given below.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top"><a href="#Alias">4.14.1 Debugger Command Aliases (‘<samp>alias</samp>’)</a></td><td> </td><td align="left" valign="top"> Debugger Command aliases
</td></tr>
<tr><td align="left" valign="top"><a href="#Annotate">4.14.2 Annotation Level (‘<samp>set annotate</samp>’)</a></td><td> </td><td align="left" valign="top"> Annotation Level (set annotate)
</td></tr>
<tr><td align="left" valign="top"><a href="#Autoeval">4.14.3 Set/Show auto-eval (‘<samp>set autoeval</samp>’)</a></td><td> </td><td align="left" valign="top"> Evaluate unrecognized commands
</td></tr>
<tr><td align="left" valign="top"><a href="#Basename">4.14.4 File basename (‘<samp>set basename</samp>’)</a></td><td> </td><td align="left" valign="top"> Show basenames of file names only (set basename)
</td></tr>
<tr><td align="left" valign="top"><a href="#Debugger">4.14.5 Allow Debugging the debugger (‘<samp>set debugger</samp>’)</a></td><td> </td><td align="left" valign="top"> Allow debugging the debugger (set debugger)
</td></tr>
<tr><td align="left" valign="top"><a href="#File">4.14.6 Specifying a Script-File Association (‘<samp>file</samp>’)</a></td><td> </td><td align="left" valign="top"> Specifying a Script-File Associaton (set file)
</td></tr>
<tr><td align="left" valign="top"><a href="#Line-Tracing">4.14.7 Show position information as statements are executed (‘<samp>set linetrace</samp>’)</a></td><td> </td><td align="left" valign="top"> Show position information (set linetrace)
</td></tr>
<tr><td align="left" valign="top"><a href="#Logging">4.14.8 Logging output (‘<samp>set logging</samp>’, ‘<samp>set logging file</samp>’...)</a></td><td> </td><td align="left" valign="top"> Specifying where to write debugger output
</td></tr>
<tr><td align="left" valign="top"><a href="#Prompt">4.14.9 Prompt (‘<samp>set prompt</samp>’, ‘<samp>show prompt</samp>’)</a></td><td> </td><td align="left" valign="top"> Prompt (set prompt, show prompt)
</td></tr>
<tr><td align="left" valign="top"><a href="#Editing">4.14.10 Command editing (‘<samp>set editing</samp>’, ‘<samp>show editing</samp>’)</a></td><td> </td><td align="left" valign="top"> Command editing (set editing, show editing)
</td></tr>
<tr><td align="left" valign="top"><a href="#Command_002dTracing">4.14.11 Debugger Commands Tracing (‘<samp>set trace-commands</samp>’, ‘<samp>show trace-commands</samp>’)</a></td><td> </td><td align="left" valign="top"> Showing commands as they run (set/show trace-commands)
</td></tr>
<tr><td align="left" valign="top"><a href="#Command-Display">4.14.12 Command Display (‘<samp>set showcommand</samp>’)</a></td><td> </td><td align="left" valign="top"> Command display (set showcommand)
</td></tr>
<tr><td align="left" valign="top"><a href="#History">4.14.13 Command history (‘<samp>H</samp>’, ‘<samp>history</samp>’, ‘<samp>!</samp>’)</a></td><td> </td><td align="left" valign="top"> Command history (history, !, H)
</td></tr>
<tr><td align="left" valign="top"><a href="#Command-Completion">4.14.14 Command Completion (‘<samp>complete</samp>’)</a></td><td> </td><td align="left" valign="top"> Command completion (complete)
</td></tr>
</table>
<hr size="6">
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</tr></table>
<a name="Debugger-Command-Aliases-_0028alias_0029"></a>
<h3 class="subsection">4.14.1 Debugger Command Aliases (‘<samp>alias</samp>’)</h3>
<dl compact="compact">
<dd><a name="index-alias-name-command"></a>
</dd>
<dt> <code>alias <var>name</var> <var>command</var></code></dt>
<dd><p>Add <var>name</var> as an alias for <var>command</var>
</p>
<a name="index-unalias-name-command"></a>
<p>Remove <var>name</var> as an alias for <var>command</var>
</p></dd>
<dt> <code>unalias <var>name</var> <var>command</var></code></dt>
</dl>
<hr size="6">
<a name="Annotate"></a>
<table cellpadding="1" cellspacing="1" border="0">
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</tr></table>
<a name="Annotation-Level-_0028set-annotate_0029"></a>
<h3 class="subsection">4.14.2 Annotation Level (‘<samp>set annotate</samp>’)</h3>
<dl compact="compact">
<dd><a name="index-set-annotate"></a>
</dd>
<dt> <code>set annotate <var>integer</var></code></dt>
<dd><p>The annotation level controls how much information the <acronym>BASH</acronym> debugger prints
in its prompt; right new it just controls whether we show full
filenames in output or the base part of the filename without path
information. Level 0 is the normal, level 1 is for use when
the <acronym>BASH</acronym> debugger is run as a subprocess of <small>GNU</small> Emacs of <acronym>DDD</acronym>,
level 2 is the maximum annotation suitable for programs that control
the <acronym>BASH</acronym> debugger.
</p></dd>
</dl>
<hr size="6">
<a name="Autoeval"></a>
<table cellpadding="1" cellspacing="1" border="0">
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</tr></table>
<a name="Set_002fShow-auto_002deval-_0028set-autoeval_0029"></a>
<h3 class="subsection">4.14.3 Set/Show auto-eval (‘<samp>set autoeval</samp>’)</h3>
<dl compact="compact">
<dd><a name="index-set-autoeval-_005b-on-_007c-1-_007c-off-_007c-0-_005d"></a>
</dd>
<dt> <code>set autoeval <span class="roman">[</span> on | 1 | off | 0 <span class="roman">]</span></code></dt>
<dd><p>Specify that debugger input that isn’t recognized as a command should
be passed to Ruby for evaluation (using the current debugged program
namespace). Note however that we <em>first</em> check input to see if it
is a debugger command and <em>only</em> if it is not do we consider it
as Ruby code. This means for example that if you have variable called
<code>n</code> and you want to see its value, you could use <code>p n</code>,
because just entering <code>n</code> will be interpreted as the debugger
“next” command.
</p>
<p>When autoeval is set on, you’ll get a different error message when you
invalid commands are encountered. Here’s a session fragment to show
the difference
</p><table><tr><td> </td><td><pre class="smallexample">bashdb<1> <b>stepp</b>
Unknown command
bashdb<2> <b>set autoeval on</b>
autoeval is on.
bashdb<3> <b>stepp</b>
NameError Exception: undefined local variable or method `stepp' for ...
</pre></td></tr></table>
<a name="index-show-autoeval"></a>
</dd>
<dt> <code>show args</code></dt>
<dd><p>Shows whether Ruby evaluation of debugger input should occur or not.
</p></dd>
</dl>
<hr size="6">
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</tr></table>
<a name="File-basename-_0028set-basename_0029"></a>
<h3 class="subsection">4.14.4 File basename (‘<samp>set basename</samp>’)</h3>
<dl compact="compact">
<dd><a name="index-set-basename"></a>
</dd>
<dt> <code>set basename <span class="roman">[</span> on | 1 <span class="roman">]</span></code></dt>
<dd><p>When set on, source filenames are shown as the shorter “basename”
only. (Directory paths are omitted). This is useful in running the
regression tests and may useful in showing debugger examples as in
this text. You may also just want less verbose filename display.
</p>
</dd>
<dt> <code>set basename <span class="roman">[</span> off | 0 <span class="roman">]</span></code></dt>
<dd><p>Source filenames are shown as with their full path. This is the default.
</p></dd>
</dl>
<hr size="6">
<a name="Debugger"></a>
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<a name="Allow-Debugging-the-debugger-_0028set-debugger_0029"></a>
<h3 class="subsection">4.14.5 Allow Debugging the debugger (‘<samp>set debugger</samp>’)</h3>
<dl compact="compact">
<dd><a name="index-set-debugger"></a>
</dd>
<dt> <code>set debugger <span class="roman">[</span> on | 1 <span class="roman">]</span></code></dt>
<dd><p>Allow the possibility of debugging this debugger. Somewhat of an
arcane thing to do. For gurus, and even he doesn’t use it all that
much.
</p></dd>
<dt> <code>set debugger <span class="roman">[</span> off | 0 <span class="roman">]</span></code></dt>
<dd><p>Don’t allow debugging into the debugger. This is the default.
</p></dd>
</dl>
<hr size="6">
<a name="File"></a>
<table cellpadding="1" cellspacing="1" border="0">
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<a name="Specifying-a-Script_002dFile-Association-_0028file_0029"></a>
<h3 class="subsection">4.14.6 Specifying a Script-File Association (‘<samp>file</samp>’)</h3>
<p>Sometimes the <acronym>BASH</acronym> debugger gets confused about where to find the script
source file for the name reported to it by bash. To resolve relative
file names that bash supplies via <code>BASH_SOURCE</code>, the <acronym>BASH</acronym> debugger uses
the current working directory when the debugged script was started as
well as the current working directory now (which might be different
if a “cd” command was issued to change the working directory).
</p>
<p>However somethimes this doesn’t work and there is a way to
override this.
</p>
<dl compact="compact">
<dd><a name="index-file"></a>
</dd>
<dt> <code>file <var>script-file</var></code></dt>
<dd><p>Directs the <acronym>BASH</acronym> debugger to use <var>script-file</var> whenever bash would have
it refers to the filename given in <code>BASH_SOURCE</code>. The filename
specified in <code>BASH_SOURCE</code> that gets overriden is shown when is
this command is issued.
</p></dd>
</dl>
<hr size="6">
<a name="Line-Tracing"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#File" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#Logging" title="Next section in reading order"> > </a>]</td>
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</tr></table>
<a name="Show-position-information-as-statements-are-executed-_0028set-linetrace_0029"></a>
<h3 class="subsection">4.14.7 Show position information as statements are executed (‘<samp>set linetrace</samp>’)</h3>
<p><acronym>BASH</acronym> has “<code>set -x</code>” tracing to show commands as they are
run. However missing from this is file and line position
information. So the debugger compensates here for what I think is
deficiency of <acronym>BASH</acronym> by providing this information. The downside
is that this tracing is slower than the built-in tracing of
<acronym>BASH</acronym>.
</p>
<p>The status of whether line tracing is enabled can be show via
<code>show linetrace</code>.
</p>
<dl compact="compact">
<dd><a name="index-set-linetrace"></a>
</dd>
<dt> <code>set linetrace <span class="roman">[</span> on | 1 <span class="roman">]</span></code></dt>
<dd><p>Turn on line tracing.
</p></dd>
<dt> <code>set linetrace <span class="roman">[</span> off | 0 <span class="roman">]</span></code></dt>
<dd><p>Turn off line tracing.
</p></dd>
</dl>
<hr size="6">
<a name="Logging"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Line-Tracing" title="Previous section in reading order"> < </a>]</td>
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</tr></table>
<a name="Logging-output-_0028set-logging_002c-set-logging-file_002e_002e_002e_0029"></a>
<h3 class="subsection">4.14.8 Logging output (‘<samp>set logging</samp>’, ‘<samp>set logging file</samp>’...)</h3>
<p>You may want to save the output of the debugger commands to a file.
There are several commands to control the debuggers’s logging.
</p>
<dl compact="compact">
<dt> <code>set logging</code></dt>
<dd><p>Prints <code>set logging</code> usage.
<a name="index-set-logging"></a>
</p></dd>
<dt> <code>set logging <span class="roman">[</span> on | 1 <span class="roman">]</span></code></dt>
<dd><p>Enable or Disable logging.
</p></dd>
<dt> <code>set logging file <var>filename</var></code></dt>
<dd><p>Change the name of the current logfile. The default logfile is
‘<tt>bashdb.txt</tt>’.
</p></dd>
<dt> <code>set logging overwrite <span class="roman">[</span> on | 1 <span class="roman">]</span></code></dt>
<dd><p>By default, the debugger will append to the logfile. Set
<code>overwrite</code> if you want <code>set logging on</code> to overwrite the
logfile instead.
</p></dd>
<dt> <code>set logging redirect <span class="roman">[</span> on | 1 <span class="roman">]</span></code></dt>
<dd><p>By default, the debugger output will go to both the terminal and the
logfile. Set <code>redirect</code> if you want output to go only to the log
file.
</p></dd>
<dt> <code>show logging</code></dt>
<dd><p>Show the current values of the logging settings.
</p></dd>
</dl>
<hr size="6">
<a name="Prompt"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Logging" title="Previous section in reading order"> < </a>]</td>
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</tr></table>
<a name="Prompt-_0028set-prompt_002c-show-prompt_0029"></a>
<h3 class="subsection">4.14.9 Prompt (‘<samp>set prompt</samp>’, ‘<samp>show prompt</samp>’)</h3>
<a name="index-prompt"></a>
<p>The <acronym>BASH</acronym> debugger indicates its readiness to read a command by printing a
string called the <em>prompt</em>. This string is normally:
</p><table><tr><td> </td><td><pre class="example">bashdb${_Dbg_less}${#_Dbg_history[@]}${_Dbg_greater}$_Dbg_space
</pre></td></tr></table>
<p>When variables inside the the prompt string are evaluated, the above
becomes something like ‘<samp>bashdb<5></samp>’ if this is the fifth command
executed or perhaps ‘<samp>bashdb<<2>></samp>’ if you have called the debugger
from inside a debugger session and this is the second command inside
the debugger session or perhaps ‘<samp>bashdb<(6)></samp>’ if you
entered a subshell after the fifth command.
</p>
<p>You can change the prompt string with the <code>set prompt</code> command,
although it is not normally advisable to do so without understanding
the implications. If you are using the <acronym>DDD</acronym> GUI, it changes the
changes the prompt and should not do so. In certain other
circumstances (such as writing a GUI like <acronym>DDD</acronym>), it may be is useful
to change the prompt.
</p>
<p><em>Note:</em> <code>set prompt</code> does not add a space for you after the
prompt you set. This allows you to set a prompt which ends in a space
or a prompt that does not. Furthermore due to a implementation
limitation (resulting from a limitation of the bash built-in function
“read”), to put a space at the end of the prompt use the
‘<samp>$_Dbg_space</samp>’ variable.
</p>
<dl compact="compact">
<dd><a name="index-set-prompt"></a>
</dd>
<dt> <code>set prompt <var>newprompt</var></code></dt>
<dd><p>Directs the <acronym>BASH</acronym> debugger to use <var>newprompt</var> as its prompt string
henceforth.
</p>
<p><em>Warning: changing the prompt can <acronym>DDD</acronym>’s ability to
understand when the debugger is waiting for input.</em>
</p>
<a name="index-show-prompt"></a>
</dd>
<dt> <code>show prompt</code></dt>
<dd><p>Prints a line of the form: ‘<samp>bashdb's prompt is: <var>your-prompt</var></samp>’
</p></dd>
</dl>
<hr size="6">
<a name="Editing"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Prompt" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#Command_002dTracing" title="Next section in reading order"> > </a>]</td>
<td valign="middle" align="left"> </td>
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<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Command-editing-_0028set-editing_002c-show-editing_0029"></a>
<h3 class="subsection">4.14.10 Command editing (‘<samp>set editing</samp>’, ‘<samp>show editing</samp>’)</h3>
<a name="index-readline"></a>
<a name="index-command-line-editing"></a>
<p>the <acronym>BASH</acronym> debugger reads its input commands through bash which uses via the
<em>readline</em> interface. This <small>GNU</small> library provides consistent
behavior for programs which provide a command line interface to the
user. Advantages are <small>GNU</small> Emacs-style or <em>vi</em>-style inline
editing of commands, <code>csh</code>-like history substitution, and a
storage and recall of command history across debugging sessions.
</p>
<p>You may control the behavior of command line editing in <acronym>BASH</acronym> with the
command <code>set</code>.
</p>
<dl compact="compact">
<dd><a name="index-set-editing"></a>
<a name="index-editing"></a>
</dd>
<dt> <code>set editing</code></dt>
<dt> <code>set editing <span class="roman">[</span> on | 1 <span class="roman">]</span></code></dt>
<dd><p>Enable command line editing (enabled by default).
</p>
</dd>
<dt> <code>set editing <span class="roman">[</span> off | 0 <span class="roman">]</span></code></dt>
<dd><p>Disable command line editing.
</p>
<a name="index-show-editing"></a>
</dd>
<dt> <code>show editing</code></dt>
<dd><p>Show whether command line editing is enabled.
</p></dd>
</dl>
<hr size="6">
<a name="Command_002dTracing"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Editing" title="Previous section in reading order"> < </a>]</td>
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Debugger-Commands-Tracing-_0028set-trace_002dcommands_002c-show-trace_002dcommands_0029"></a>
<h3 class="subsection">4.14.11 Debugger Commands Tracing (‘<samp>set trace-commands</samp>’, ‘<samp>show trace-commands</samp>’)</h3>
<a name="index-tracing-debugger-commands"></a>
<p>If you need to debug user-defined commands or sourced files you may find it
useful to enable <em>command tracing</em>. In this mode each command will be
printed as it is executed, prefixed with one or more ‘<samp>+</samp>’ symbols, the
quantity denoting the call depth of each command.
</p>
<dl compact="compact">
<dd><a name="index-set-trace_002dcommands"></a>
<a name="index-command-scripts_002c-debugging"></a>
</dd>
<dt> <code>set trace-commands on</code></dt>
<dd><p>Enable command tracing.
</p></dd>
<dt> <code>set trace-commands off</code></dt>
<dd><p>Disable command tracing.
</p></dd>
<dt> <code>show trace-commands</code></dt>
<dd><p>Display the current state of command tracing.
</p></dd>
</dl>
<hr size="6">
<a name="Command-Display"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Command_002dTracing" title="Previous section in reading order"> < </a>]</td>
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Command-Display-_0028set-showcommand_0029"></a>
<h3 class="subsection">4.14.12 Command Display (‘<samp>set showcommand</samp>’)</h3>
<p>The debugger normally lists the line number and source line of the for
the statement to be next executed. Often this line contains one
expression or one statement and it is clear from this line what’s
going to happen. However <acronym>BASH</acronym> allows many expressions or
statements to be put on a single source line; some lines
contain several units of execution. Some examples of this
behavior are listed below:
</p>
<table><tr><td> </td><td><pre class="smallexample">x=1; y=2; x=3
(( x > 5 )) && x=5
y=`echo *`
</pre></td></tr></table>
<p>In the first line of the example above, we have three assignment
statements on a single line. In the second line of the example above
we have a statement which gets run only if a condition tests true. And
in the third line of the example above, we have a command that gets
run and then the output of that is substituted in an assignemnt
statement. If you were single stepping inside the debugger, each line
might get listed more than once before each of the actions that might
get performed. (In the case of the conditional statement, the
line gets listed only once when the condition is false.)
</p>
<p>In order to assist understanding where you are, the enhanced version
of <acronym>BASH</acronym> maintains a dynamic variable <code>BASH_COMMAND</code> that
contains piece of code next to be run (or is currently being run). The
debugger has arranged to save this and can display this information
or not. This is controlled by <code>set showcommand</code>.
</p>
<dl compact="compact">
<dd><a name="index-set-showcommand"></a>
</dd>
<dt> <code>set showcommand <span class="roman">[</span>auto | on | 1 | off | 0 <span class="roman">]</span></code></dt>
<dd><p>controls whether or not to show the saved <code>BASH_COMMAND</code> for the
command next to be executed.
</p></dd>
</dl>
<p>When the value is <code>auto</code> the following heuristic is used to
determine whether or not to display the saved <code>BASH_COMMAND</code>. If
the last time you stopped you were at the same place and the command
string has changed, then show the command. When the value <code>on</code> is
used, the debugger always shows <code>BASH_COMMAND</code> and when
<code>off</code> is used, the debugger nevers shows
<code>BASH_COMMAND</code>. Note that listing the text of the source line is
independent of whether or not the command is also listed.
</p>
<p>Some examples:
</p><table><tr><td> </td><td><pre class="smallexample">set showcommand auto <b>This is the default</b>
set showcommand on <b>Always show the next command to be executed</b>
set showcommand off <b>Never show the next command to be executed</b>
</pre></td></tr></table>
<hr size="6">
<a name="History"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Command-Display" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#Command-Completion" title="Next section in reading order"> > </a>]</td>
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Command-history-_0028H_002c-history_002c-_0021_0029"></a>
<h3 class="subsection">4.14.13 Command history (‘<samp>H</samp>’, ‘<samp>history</samp>’, ‘<samp>!</samp>’)</h3>
<p>The <acronym>BASH</acronym> debugger can keep track of the commands you type during your
debugging sessions, so that you can be certain of precisely what
happened. If the prompt has not been changed (see <a href="#Prompt">Prompt</a>), the history number that will be in use next is by default
listed in the debugger prompt. Invalid commands and history commands
are not saved on the history stack.
</p>
<dl compact="compact">
<dd><a name="index-H-_005bstart_002dnumber-_005bend_002dnumber_005d_005d"></a>
</dd>
<dt> <code>H <span class="roman">[</span><var>start-number</var> <span class="roman">[</span><var>end-number</var><span class="roman">]</span><span class="roman">]</span></code></dt>
<dt> <code>H <span class="roman">[</span><var>-count</var><span class="roman">]</span></code></dt>
<dt> <code>!<span class="roman">[</span>-<span class="roman">]</span><var>n</var>:p</code></dt>
<dd>
<p>You can list what is in the history stack with <code>H</code>. Debugger
commands in ths history stack are listed from most recent to least recent.
If no <var>start-number</var> is given we start with the most recently
executed command and end with the first entry in the history stack.
If <var>start-number</var> is given, that history number is listed first. If
<var>end-number</var> is given, that history number is listed last. If a
single negative number is given list that many history commands.
</p>
<p>An alternate form is <code>!<em>n</em>:p</code> or <code>!-<em>n</em>:p</code> where
<em>n</em> is an integer. If a minus sign is used, <em>n</em> is taken as
the count to go back from the end rather than as a absolute history
number. In contrast <code>H</code>, this form only prints a <em>single</em>
history item.
</p>
<p>Some examples:
</p><table><tr><td> </td><td><pre class="smallexample">H <b>List entire history</b>
H -2 <b>List the last two history items</b>
!-2:p <b>List a single history item starting at the same place as above</b>
H 5 <b>List history from history number 5 to the begining (number 0)</b>
H 5 0 <b>Same as above</b>
H 5 3 <b>List history from history number 5 down to history number 3</b>
!5:p <b>List a single history item 5</b>
</pre></td></tr></table>
<a name="index-history-_005b_002d_005d_005bn_005d"></a>
<a name="index-_0021_005b_002d_005dn-_0028history_0029"></a>
</dd>
<dt> <code>history <span class="roman">[</span><span class="roman">[</span>-<span class="roman">]</span><var>n</var><span class="roman">]</span></code></dt>
<dt> <code>!<span class="roman">[</span>-<span class="roman">]</span><var>n</var></code></dt>
<dd>
<p>Use this command to reexecute a given history number. If no number is
given, the last debugger command in the history is executed.
</p>
<p>An alternate form is <code>!<em>n</em></code> or <code>!-<em>n</em></code> where
<em>n</em> is an integer.
</p>
<p>If a minus sign is used in in either form, <em>n</em> is taken as the
count to go back from the end rather than as a absolute history
number.
</p>
</dd>
</dl>
<p>Use these commands to manage the the <acronym>BASH</acronym> debugger command
history facility.
</p>
<dl compact="compact">
<dd>
<a name="index-history-save"></a>
<a name="index-set-history-save"></a>
</dd>
<dt> <code>set history save</code></dt>
<dt> <code>set history save <span class="roman">[</span> on | 1 <span class="roman">]</span></code></dt>
<dd><p>Record command history in a file, whose name may be specified with the
<code>set history filename</code> command. By default, this option is enabled.
</p>
</dd>
<dt> <code>set history save <span class="roman">[</span> off | 0 <span class="roman">]</span></code></dt>
<dd><p>Stop recording command history in a file.
</p>
<a name="index-history-size"></a>
<a name="index-set-history-size"></a>
</dd>
<dt> <code>set history size <var>size</var></code></dt>
<dd><p>Set the number of commands which <acronym>BASH</acronym> keeps in its history list.
This defaults to the value of the environment variable
<code>HISTSIZE</code>, or to 256 if this variable is not set.
</p></dd>
</dl>
<dl compact="compact">
<dd>
<a name="index-show-history"></a>
</dd>
<dt> <code>show history</code></dt>
<dt> <code>show history save</code></dt>
<dt> <code>show history size</code></dt>
<dd><p>These commands display the state of the <acronym>BASH</acronym> history parameters.
<code>show history</code> by itself displays all states.
</p></dd>
</dl>
<dl compact="compact">
<dd><a name="index-shows"></a>
</dd>
<dt> <code>show commands</code></dt>
<dd><p>Display the last ten commands in the command history.
</p>
</dd>
<dt> <code>show commands <var>n</var></code></dt>
<dd><p>Print ten commands centered on command number <var>n</var>.
</p>
</dd>
<dt> <code>show commands +</code></dt>
<dd><p>Print ten commands just after the commands last printed.
</p></dd>
</dl>
<hr size="6">
<a name="Command-Completion"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#History" title="Previous section in reading order"> < </a>]</td>
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Command-Completion-_0028complete_0029"></a>
<h3 class="subsection">4.14.14 Command Completion (‘<samp>complete</samp>’)</h3>
<p>The <code>complete <var>args</var></code> command lists all the possible
completions for the beginning of a command. We can also show
completions for <code>set</code>, <code>show</code> and <code>info</code>
subcommands. Use <var>args</var> to specify the beginning of the command
you want completed. For example:
</p>
<table><tr><td> </td><td><pre class="smallexample">complete d
</pre></td></tr></table>
<p>results in:
</p>
<table><tr><td> </td><td><pre class="smallexample">d
debug
delete
disable
display
deleteall
down
</pre></td></tr></table>
<p>And
</p><table><tr><td> </td><td><pre class="smallexample">complete set a
</pre></td></tr></table>
<p>results in:
</p>
<table><tr><td> </td><td><pre class="smallexample">set args
set annotate
</pre></td></tr></table>
<p>This is intended for use by front-ends such as <small>GNU</small>
Emacs and <small>DDD</small>.
</p>
<hr size="6">
<a name="Front-Ends"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Command-Completion" title="Previous section in reading order"> < </a>]</td>
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</tr></table>
<a name="Using-the-BASH-debugger-from-a-front_002dend-user-interface"></a>
<h1 class="chapter">5. Using the <acronym>BASH</acronym> debugger from a front-end user interface</h1>
<p>There are some front-ends that can use the <acronym>BASH</acronym> debugger as a back-end
debugger.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top"><a href="#Emacs">5.1 Using the <acronym>BASH</acronym> debugger from <small>GNU</small> Emacs</a></td><td> </td><td align="left" valign="top"></td></tr>
<tr><td align="left" valign="top"><a href="#DDD">5.2 Using the <acronym>BASH</acronym> debugger from <acronym>DDD</acronym></a></td><td> </td><td align="left" valign="top"></td></tr>
</table>
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<a name="Using-the-BASH-debugger-from-GNU-Emacs"></a>
<h2 class="section">5.1 Using the <acronym>BASH</acronym> debugger from <small>GNU</small> Emacs</h2>
<a name="index-Emacs"></a>
<a name="index-GNU-Emacs"></a>
<p>A special interface allows you to use <small>GNU</small> Emacs to view (and
edit) the source files for the program you are debugging with
the <acronym>BASH</acronym> debugger. However you must be using <small>GNU</small> Emacs version 21 or
greater. (<code>M-x show-emacs-version</code> inside <small>GNU</small> Emacs will
tell you what version you are running.)
</p>
<p>To use this interface, use the command <kbd>M-x bashdb</kbd> in <small>GNU</small>
Emacs. Give the executable file you want to debug as an
argument. Make sure to use the version that comes with this package as
this is newer than that supplied with <small>GNU</small> Emacs.
</p>
<p>The <kbd>bashdb</kbd> command starts the <acronym>BASH</acronym> debugger as a subprocess of Emacs,
with input and output through a newly created Emacs buffer.
</p>
<p>Using the <acronym>BASH</acronym> debugger under Emacs is just like using the <acronym>BASH</acronym> debugger
normally except for two things:
</p>
<ul>
<li>
All “terminal” input and output goes through the GNU Emacs buffer.
</li></ul>
<p>This applies both to the <acronym>BASH</acronym> debugger commands and their output, and to the input
and output done by the program you are debugging.
</p>
<p>This is useful because it means that you can copy the text of previous
commands and input them again; you can even use parts of the output
in this way.
</p>
<p>All the facilities of GNU Emacs’ Shell mode are available for interacting
with your script. In particular, you can send signals the usual
way—for example, <kbd>C-c C-c</kbd> for an interrupt, <kbd>C-c C-z</kbd> for a
stop.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top"><a href="#GUD">5.1.1 Commands from the GUD buffer</a></td><td> </td><td align="left" valign="top"></td></tr>
<tr><td align="left" valign="top"><a href="#Emacs-Source">5.1.2 Commands from the source script</a></td><td> </td><td align="left" valign="top"></td></tr>
<tr><td align="left" valign="top"><a href="#Emacs-Shell">5.1.3 the <acronym>BASH</acronym> debugger from a <small>GNU</small> Emacs Shell</a></td><td> </td><td align="left" valign="top"></td></tr>
</table>
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Commands-from-the-GUD-buffer"></a>
<h3 class="subsection">5.1.1 Commands from the GUD buffer</h3>
<ul>
<li>
the <acronym>BASH</acronym> debugger displays source code through Emacs.
</li></ul>
<p>Each time the <acronym>BASH</acronym> debugger displays a stack frame, Emacs automatically finds the
source file for that frame and puts an arrow (‘<samp>=></samp>’) at the
left margin of the current line. Emacs uses a separate buffer for
source display, and splits the screen to show both your the <acronym>BASH</acronym> debugger session
and the source.
</p>
<p>Explicit the <acronym>BASH</acronym> debugger <code>list</code> or search commands still produce output as
usual, but you probably have no reason to use them from GNU Emacs.
</p>
<blockquote><p><em>Warning:</em> If the directory where your script resides is not your
current directory, it can be easy to confuse Emacs about the location of
the source files, in which case the auxiliary display buffer does not
appear to show your source. the <acronym>BASH</acronym> debugger can find programs by searching your
environment’s <code>PATH</code> variable, so the the <acronym>BASH</acronym> debugger input and output
session proceeds normally; but Emacs does not get enough information
back from the <acronym>BASH</acronym> debugger to locate the source files in this situation. To
avoid this problem, either start the <acronym>BASH</acronym> debugger mode from the directory where
your script resides, or specify an absolute file name when prompted for the
<kbd>M-x gdb</kbd> argument.
</p>
<p>A similar confusion can result if you use the the <acronym>BASH</acronym> debugger <code>file</code> command to
switch to debugging a program in some other location, from an existing
the <acronym>BASH</acronym> debugger buffer in Emacs.
</p></blockquote>
<p>By default, <kbd>M-x bashdb</kbd> calls the <code>bash --debugger</code>. If you
need to call the <acronym>BASH</acronym> debugger by a different name (for example, if you
keep several configurations around, with different names) you can set
the Emacs variable <code>gud-bashdb-command-name</code>; for example,
</p>
<table><tr><td> </td><td><pre class="example">(setq gud-bashdb-command-name "bash --debugger")
</pre></td></tr></table>
<p>(preceded by <kbd>M-:</kbd> or <kbd>ESC :</kbd>, or typed in the <code>*scratch*</code> buffer, or
in your ‘<tt>.emacs</tt>’ file) makes Emacs call the program named
“<code>bash-debugger</code>” instead.
</p>
<p>In the the <acronym>BASH</acronym> debugger I/O buffer, you can use the Emacs commands listed
below in addition to the standard Shell mode commands. The I/O buffer
name name is usually <code>*gud-</code><em>script-name</em><code>*</code>, where
<em>script-name</em> is the name of the script you are debugging.
</p>
<p>Many of the commands listed below are also bound to a second key
sequence which also can be used in the also be used in the source
script. These are listed in <a href="#Emacs-Source">Commands from the source script</a>.
</p>
<dl compact="compact">
<dt> <kbd>C-h m</kbd></dt>
<dd><p>Describe the features of Emacs’ the <acronym>BASH</acronym> debugger Mode.
</p>
</dd>
<dt> <kbd>C-c C-f</kbd></dt>
<dd><p>Execute until exit from the selected stack frame. The Same as the <acronym>BASH</acronym> debugger
<code>finish</code> command. The <small>GNU</small> Emacs command name is
<code>gud-finish</code> and <code>C-x C-a f C-f</code> is an alternate binding
which also can be used in the source script. See section <a href="#Finish">Finish (‘<samp>finish</samp>’)</a>.
</p>
</dd>
<dt> <kbd>C-c C-l</kbd></dt>
<dd><p>Resynchronize the current position with the source window. The
<small>GNU</small> Emacs command name is <code>gud-refresh</code> and <code>C-x C-a
C-l</code> is an alternate binding which also can be used in the source script.
</p>
</dd>
<dt> <kbd>C-c C-n</kbd></dt>
<dd><p>Execute to next source line in this function, skipping all function
calls. Same as the <acronym>BASH</acronym> debugger <code>next</code> command. The <small>GNU</small> Emacs
command name is <code>gud-next</code> and <code>C-x C-a n</code> is an
alternate binding which also can be used in the source script. See section <a href="#Next">Next (‘<samp>next</samp>’)</a>.
</p>
<p>With a numeric argument, run that many times.
See <a href="Emacs.html#Arguments">(Emacs)Arguments</a> section ‘Numeric Arguments’ in <cite>The <small>GNU</small> Emacs Manual</cite>.
</p>
</dd>
<dt> <kbd>C-c C-r</kbd></dt>
<dd><p>Continue execution of your script Same as the <acronym>BASH</acronym> debugger <code>continue</code>
command. The <small>GNU</small> Emacs command name is <code>gud-cont</code> and
<code>C-x C-a C-r</code> is an alternate binding which also can be used in the
source script. See <a href="#Continue">Continue (‘<samp>continue</samp>’)</a>.
</p>
</dd>
<dt> <kbd>C-c C-s</kbd></dt>
<dd><p>Step one source line. Same as the <acronym>BASH</acronym> debugger <code>step</code> command. The
<small>GNU</small> Emacs command name is <code>gud-step</code> and <code>C-x C-a C-s</code>
is an alternate binding which can be used in the source
script. See section <a href="#Step">Step (‘<samp>step</samp>’)</a>.
</p>
<p>With a numeric argument, run that many times.
See <a href="Emacs.html#Arguments">(Emacs)Arguments</a> section ‘Numeric Arguments’ in <cite>The <small>GNU</small> Emacs Manual</cite>.
</p>
</dd>
<dt> <kbd>C-c ></kbd></dt>
<dd><p>Go down a stack frame. Same as the <acronym>BASH</acronym> debugger <code>down</code>.
With a numeric argument, go down that many stack frames.
See <a href="Emacs.html#Arguments">(Emacs)Arguments</a> section ‘Numeric Arguments’ in <cite>The <small>GNU</small> Emacs Manual</cite>.
</p>
<p>The <small>GNU</small> Emacs command name is
<code>gud-down</code> and <code>C-x C-a ></code> is an alternate binding
which can be used in the source script.
</p>
</dd>
<dt> <kbd>C-c <</kbd></dt>
<dd><p>Go up a stack frame. With a numeric argument, go up that many
stack frames. Same the <acronym>BASH</acronym> debugger <code>up</code> command.
See <a href="Emacs.html#Arguments">(Emacs)Arguments</a> section ‘Numeric Arguments’ in <cite>The <small>GNU</small> Emacs Manual</cite>.
</p>
<p>The <small>GNU</small> Emacs command name is
<code>gud-up</code> and <code>C-x C-a <</code> is an alternate binding
which can be used in the source script.
</p>
</dd>
<dt> <kbd>C-c a</kbd></dt>
<dd><p>Shows argument variables (e.g. <code>$1</code>, <code>$2</code>) of the current
stack frame. Same as the <acronym>BASH</acronym> debugger <code>info args</code> command. The
<small>GNU</small> Emacs command name is <code>gud-args</code> and <code>C-x C-a a</code> is
an alternate binding which also can be used in the source script.
</p>
</dd>
<dt> <kbd>C-c R</kbd></dt>
<dd><p>Restart or run the script. Same as the <acronym>BASH</acronym> debugger <code>run</code> command. The
<small>GNU</small> Emacs command name is <code>gud-finish</code> and <code>C-x C-a R</code>
is an alternate binding which also can be used in the source script.
</p>
</dd>
<dt> <kbd>C-c T</kbd></dt>
<dd><p>Show stack trace. Same as the <acronym>BASH</acronym> debugger <code>where</code> command. The
<small>GNU</small> Emacs command name is <code>gud-where</code> and <code>C-x C-a T</code> is
an alternate binding which can be used in the source
script. See section <a href="#Backtrace">Backtraces (‘<samp>where</samp>’)</a>.
</p>
</dd>
</dl>
<p>In any source file, the Emacs command <kbd>C-x SPC</kbd> (<code>gud-break</code>)
tells the <acronym>BASH</acronym> debugger to set a breakpoint on the source line point is on.
</p>
<p>If you accidentally delete the source-display buffer, an easy way to get
it back is to type the command <code>frame</code> in the the <acronym>BASH</acronym> debugger buffer, to
request a frame display; when you run under Emacs, this recreates
the source buffer if necessary to show you the context of the current
frame.
</p>
<p>The source files displayed in Emacs are in ordinary Emacs buffers
which are visiting the source files in the usual way. You can edit
the files with these buffers if you wish; but keep in mind that the <acronym>BASH</acronym> debugger
communicates with Emacs in terms of line numbers. If you add or
delete lines from the text, the line numbers that the <acronym>BASH</acronym> debugger knows cease
to correspond properly with the code.
</p>
<p>See <a href="Emacs.html#Debugger-Operation">(Emacs)Debugger Operation</a> section ‘Debugger Operation’ in <cite>The <small>GNU</small> Emacs Manual</cite>.
</p>
<hr size="6">
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</tr></table>
<a name="Commands-from-the-source-script"></a>
<h3 class="subsection">5.1.2 Commands from the source script</h3>
<dl compact="compact">
<dt> <kbd>C-x SPC</kbd></dt>
<dd>
<p>tells the <acronym>BASH</acronym> debugger to set a breakpoint on the source
line point is on. (<code>gud-break</code>)
</p>
</dd>
<dt> <kbd>C-x C-a t</kbd> </dt>
<dd>
<p><code>gud-linetrace</code>
</p>
</dd>
<dt> <kbd>C-x C-a C-f</kbd></dt>
<dd><p>Restart or run the script. Same as the <acronym>BASH</acronym> debugger <code>run</code> command. The
<small>GNU</small> Emacs command name is <code>gud-finish</code>. In the corresponding
I/O buffer, <code>C-c R</code> is an alternate binding.
</p>
</dd>
<dt> <kbd>C-x C-a T</kbd> </dt>
<dd><p>Show stack trace. Same as the <acronym>BASH</acronym> debugger <code>where</code> command. In the
corresponding I/O buffer, <code>C-c T</code> is an alternate
binding. See section <a href="#Backtrace">Backtraces (‘<samp>where</samp>’)</a>.
</p>
</dd>
<dt> <kbd>C-x C-a <</kbd> </dt>
<dd>
<p>Go up a stack frame. With a numeric argument, go up that many
stack frames. Same the <acronym>BASH</acronym> debugger <code>up</code> command.
See <a href="Emacs.html#Arguments">(Emacs)Arguments</a> section ‘Numeric Arguments’ in <cite>The <small>GNU</small> Emacs Manual</cite>.
</p>
<p>The <small>GNU</small> Emacs command name is <code>gud-up</code>. In the corresponding
I/O buffer, <code>C-c <</code> is an alternate binding.
</p>
</dd>
<dt> <kbd>C-x C-a ></kbd> </dt>
<dd>
<p>Go down a stack frame. Same as the <acronym>BASH</acronym> debugger <code>down</code>.
With a numeric argument, go down that many stack frames.
See <a href="Emacs.html#Arguments">(Emacs)Arguments</a> section ‘Numeric Arguments’ in <cite>The <small>GNU</small> Emacs Manual</cite>.
</p>
<p>The <small>GNU</small> Emacs command name is <code>gud-down</code>. In the
corresponding I/O buffer, <code>C-c ></code> is an alternate binding.
</p>
</dd>
<dt> <kbd>C-x C-a C-t</kbd></dt>
<dd>
<p><code>gud-tbreak</code>
</p>
</dd>
<dt> <kbd>C-x C-a C-s</kbd></dt>
<dd>
<p>Step one source line. Same as the <acronym>BASH</acronym> debugger <code>step</code>
command. See section <a href="#Step">Step (‘<samp>step</samp>’)</a>.
</p>
<p>With a numeric argument, run that many times.
See <a href="Emacs.html#Arguments">(Emacs)Arguments</a> section ‘Numeric Arguments’ in <cite>The <small>GNU</small> Emacs Manual</cite>.
</p>
<p>The <small>GNU</small> Emacs command name is <code>gud-step</code>. In the
corresponding I/O buffer, <code>C-c C-s</code> is an alternate binding.
</p>
</dd>
<dt> <kbd>C-x C-a C-e</kbd></dt>
<dd>
<p><code>gud-statement</code>
</p>
</dd>
<dt> <kbd>C-x C-a R</kbd> </dt>
<dd><p>Restart or run the script. Same as the <acronym>BASH</acronym> debugger <code>run</code> command. The
<small>GNU</small> Emacs command name is <code>gud-run</code>. In the corresponding I/O
buffer, <code>C-c R</code> is an alternate binding.
</p>
</dd>
<dt> <kbd>C-x C-a C-d</kbd></dt>
<dd><p>Delete breakpoint. <code>gud-remove</code>
</p>
</dd>
<dt> <kbd>C-x C-a C-p</kbd></dt>
<dd>
<p><code>gud-print</code>
</p>
</dd>
<dt> <kbd>C-x C-a C-n</kbd></dt>
<dd>
<p>Execute to next source line in this function, skipping all function
calls. Same as the <acronym>BASH</acronym> debugger <code>next</code> command. With a numeric
argument, run that many times. See <a href="Emacs.html#Arguments">(Emacs)Arguments</a> section ‘Numeric Arguments’ in <cite>The <small>GNU</small> Emacs Manual</cite>.
</p>
<p>The <small>GNU</small> Emacs command name is <code>gud-next</code>. In the
corresponding I/O buffer, <code>C-c C-n</code> is an alternate binding.
</p>
</dd>
<dt> <kbd>C-x C-a f C-f</kbd></dt>
<dd>
<p><code>gud-finish</code>
</p>
</dd>
<dt> <kbd>C-x C-a C-r</kbd></dt>
<dd><p>Continue execution of your script Same as the <acronym>BASH</acronym> debugger <code>continue</code>
command. The <small>GNU</small> Emacs command name is <code>gud-cont</code>. In the
corresponding I/O buffer, <code>C-c C-r</code> is an alternate binding. See
<a href="#Continue">Continue (‘<samp>continue</samp>’)</a>.
</p>
</dd>
<dt> <kbd>C-x C-a C-b</kbd></dt>
<dd>
<p><code>gud-break</code>
</p>
</dd>
<dt> <kbd>C-x C-a a</kbd> </dt>
<dd>
<p><code>gud-args</code>
Shows argument variables (e.g. <code>$1</code>, <code>$2</code>) of the current
stack frame. Same as the <acronym>BASH</acronym> debugger <code>info args</code> command. The
<small>GNU</small> Emacs command name is <code>gud-args</code>. In the corresponding
I/O buffer, <code>C-c a</code> is an alternate binding which also can be
used in the source script.
</p>
</dd>
<dt> <kbd>C-x C-a C-l</kbd></dt>
<dd><p>Move to current position in this source window. The <small>GNU</small> Emacs
command name is <code>gud-refresh</code>. In the corresponding I/O buffer,
<code>C-c C-l</code> is an alternate binding.
</p>
</dd>
</dl>
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</tr></table>
<a name="the-BASH-debugger-from-a-GNU-Emacs-Shell"></a>
<h3 class="subsection">5.1.3 the <acronym>BASH</acronym> debugger from a <small>GNU</small> Emacs Shell</h3>
<p>It is also possible in GNU emacs to use a regular (“comint”) shell
and set a mode to watch for the <acronym>BASH</acronym> debugger prompts. See <a href="Emacs.html#Interactive-Shell">(Emacs)Interactive Shell</a> section ‘Shell’ in <cite>The <small>GNU</small> Emacs Manual</cite>.
</p>
<p>To run bash in a shell in Emacs but track source lines this, issue the
the command (from M-x) <code>turn-on-bashdbtrack</code>. There is some
overhead involved in scanning output, so if you are not debugging bash
programs you probably want to turn this off which can be done via the
M-x <code>turn-off-bashdbtrack</code> command.
</p>
<hr size="6">
<a name="DDD"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Emacs-Shell" title="Previous section in reading order"> < </a>]</td>
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<td valign="middle" align="left"> </td>
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</tr></table>
<a name="Using-the-BASH-debugger-from-DDD"></a>
<h2 class="section">5.2 Using the <acronym>BASH</acronym> debugger from <acronym>DDD</acronym></h2>
<a name="index-DDD"></a>
<p>the <acronym>BASH</acronym> debugger support is rather new in <acronym>DDD</acronym>. As a programming
language, the <acronym>BASH</acronym> debugger is not feature rich: there are no record
structures or hash tables (yet), no pointers, package variable scoping
or methods. So much of the data display and visualization features of
<acronym>DDD</acronym> are disabled.
</p>
<p>As with any scripting or interpreted language (e.g. Perl), one can’t
step by a single machine-language instruction. So the ddd Stepi/Nexti
commands are disabled.
</p>
<p>Some <acronym>BASH</acronym> settings are essential for <acronym>DDD</acronym> to work
correctly. These settings with their correct values are:
</p>
<table><tr><td> </td><td><pre class="example">set annotate 1
set prompt set prompt bashdb$_Dbg_less$_Dbg_greater$_Dbg_space
</pre></td></tr></table>
<p><acronym>DDD</acronym> sets these values automatically when invoking
<acronym>BASH</acronym>; if these values are changed, there may be some
malfunctions.
</p>
<p>Pay special attention when the prompt has extra angle brackets (a
nested shell) or has any parenthesis (is in a subshell). Quitting may
merely exit out of one of these nested (sub)shells rather than leave
the program.
</p>
<hr size="6">
<a name="BASH-Debugger-Bugs"></a>
<table cellpadding="1" cellspacing="1" border="0">
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Reporting-Bugs"></a>
<h1 class="chapter">6. Reporting Bugs</h1>
<a name="index-bugs"></a>
<a name="index-reporting-bugs"></a>
<p>Your bug reports play an essential role in making the <acronym>BASH</acronym>
debugger reliable.
</p>
<p>Reporting a bug may help you by bringing a solution to your problem, or it
may not. But in any case the principal function of a bug report is to help
the entire community by making the next version of the <acronym>BASH</acronym> debugger work better. Bug
reports are your contribution to the maintenance of the <acronym>BASH</acronym> debugger.
</p>
<p>In order for a bug report to serve its purpose, you must include the
information that enables us to fix the bug.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top"><a href="#Bug-Criteria">6.1 Have you found a bug?</a></td><td> </td><td align="left" valign="top"></td></tr>
<tr><td align="left" valign="top"><a href="#Bug-Reporting">6.2 How to report bugs</a></td><td> </td><td align="left" valign="top"></td></tr>
</table>
<hr size="6">
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Have-you-found-a-bug_003f"></a>
<h2 class="section">6.1 Have you found a bug?</h2>
<a name="index-bug-criteria"></a>
<p>If you are not sure whether you have found a bug, here are some guidelines:
</p>
<ul>
<li><a name="index-fatal-signal"></a>
<a name="index-debugger-crash"></a>
<a name="index-crash-of-debugger"></a>
</li><li>
If the debugger gets a fatal signal, for any input whatever, that is a
the <acronym>BASH</acronym> debugger bug. Reliable debuggers never crash.
<a name="index-error-on-valid-input"></a>
</li><li>
If the <acronym>BASH</acronym> debugger produces an error message for valid input, that is a
bug. (Note that if you’re cross debugging, the problem may also be
somewhere in the connection to the target.)
<a name="index-invalid-input"></a>
</li><li>
If the <acronym>BASH</acronym> debugger does not produce an error message for invalid input,
that is a bug. However, you should note that your idea of
“invalid input” might be our idea of “an extension” or “support
for traditional practice”.
</li><li>
If you are an experienced user of debugging tools, your suggestions
for improvement of the <acronym>BASH</acronym> debugger are welcome in any case.
</li></ul>
<hr size="6">
<a name="Bug-Reporting"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Bug-Criteria" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#History-and-Acknowledgments" title="Next section in reading order"> > </a>]</td>
<td valign="middle" align="left"> </td>
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<td valign="middle" align="left">[<a href="#BASH-Debugger-Bugs" title="Up section"> Up </a>]</td>
<td valign="middle" align="left">[<a href="#History-and-Acknowledgments" title="Next chapter"> >> </a>]</td>
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="How-to-report-bugs"></a>
<h2 class="section">6.2 How to report bugs</h2>
<a name="index-bug-reports"></a>
<a name="index-BASH-debugger-bugs_002c-reporting"></a>
<p>Bug reports can sent via the sourceforge bug tracking mechansim at
<a href="http://sourceforge.net/tracker/?group_id=61395&atid=497159">http://sourceforge.net/tracker/?group_id=61395&atid=497159</a>. Of
course patches are very much welcome too. Those can also be sent via
the same mechanism.
</p>
<p>The fundamental principle of reporting bugs usefully is this:
<strong>report all the facts</strong>. If you are not sure whether to state a
fact or leave it out, state it!
</p>
<p>Often people omit facts because they think they know what causes the
problem and assume that some details do not matter. Thus, you might
assume that the name of the variable you use in an example does not matter.
Well, probably it does not, but one cannot be sure. Perhaps the bug is a
stray memory reference which happens to fetch from the location where that
name is stored in memory; perhaps, if the name were different, the contents
of that location would fool the debugger into doing the right thing despite
the bug. Play it safe and give a specific, complete example. That is the
easiest thing for you to do, and the most helpful.
</p>
<p>Keep in mind that the purpose of a bug report is to enable us to fix the
bug. It may be that the bug has been reported previously, but neither
you nor we can know that unless your bug report is complete and
self-contained.
</p>
<p>Sometimes people give a few sketchy facts and ask, “Does this ring a
bell?” Those bug reports are useless, and we urge everyone to
<em>refuse to respond to them</em> except to chide the sender to report
bugs properly.
</p>
<p>To enable us to fix the bug, you should include all these things:
</p>
<ul>
<li>
The version of the <acronym>BASH</acronym> debugger. the <acronym>BASH</acronym> debugger announces it if you start
with no arguments; you can also print it at any time using <code>version</code>
command.
<p>Without this, we will not know whether there is any point in looking for
the bug in the current version of the <acronym>BASH</acronym> debugger.
</p>
</li><li>
The type of machine you are using, and the operating system name and
version number.
</li><li>
What compiler (and its version) was used to compile BASH—e.g.
“gcc 3.4”.
</li><li>
The command arguments you gave the compiler to compile your example and
observe the bug. For example, did you use ‘<samp>-O</samp>’? To guarantee
you will not omit something important, list them all. A copy of the
Makefile (or the output from make) is sufficient.
<p>If we were to try to guess the arguments, we would probably guess wrong
and then we might not encounter the bug.
</p>
</li><li>
A complete input script, and all necessary source files, that will
reproduce the bug.
</li><li>
A description of what behavior you observe that you believe is
incorrect. For example, “It gets a fatal signal.”
<p>Of course, if the bug is that the <acronym>BASH</acronym> debugger gets a fatal signal, then we
will certainly notice it. But if the bug is incorrect output, we might
not notice unless it is glaringly wrong. You might as well not give us
a chance to make a mistake.
</p>
<p>Even if the problem you experience is a fatal signal, you should still
say so explicitly. Suppose something strange is going on, such as, your
copy of the <acronym>BASH</acronym> debugger is out of synch, or you have encountered a bug in
the C library on your system. (This has happened!) Your copy might
crash and ours would not. If you told us to expect a crash, then when
ours fails to crash, we would know that the bug was not happening for
us. If you had not told us to expect a crash, then we would not be able
to draw any conclusion from our observations.
</p>
</li><li>
If you wish to suggest changes to the the <acronym>BASH</acronym> debugger source, send us context
diffs. If you even discuss something in the the <acronym>BASH</acronym> debugger source, refer to
it by context, not by line number.
<p>The line numbers in our development sources will not match those in your
sources. Your line numbers would convey no useful information to us.
</p>
</li></ul>
<p>Here are some things that are not necessary:
</p>
<ul>
<li>
A description of the envelope of the bug.
<p>Often people who encounter a bug spend a lot of time investigating
which changes to the input file will make the bug go away and which
changes will not affect it.
</p>
<p>This is often time consuming and not very useful, because the way we
will find the bug is by running a single example under the debugger
with breakpoints, not by pure deduction from a series of examples.
We recommend that you save your time for something else.
</p>
<p>Of course, if you can find a simpler example to report <em>instead</em>
of the original one, that is a convenience for us. Errors in the
output will be easier to spot, running under the debugger will take
less time, and so on.
</p>
<p>However, simplification is not vital; if you do not want to do this,
report the bug anyway and send us the entire test case you used.
</p>
</li><li>
A patch for the bug.
<p>A patch for the bug does help us if it is a good one. But do not omit
the necessary information, such as the test case, on the assumption that
a patch is all we need. We might see problems with your patch and decide
to fix the problem another way, or we might not understand it at all.
</p>
<p>Sometimes with a program as complicated as the <acronym>BASH</acronym> debugger it is very hard to
construct an example that will make the program follow a certain path
through the code. If you do not send us the example, we will not be able
to construct one, so we will not be able to verify that the bug is fixed.
</p>
<p>And if we cannot understand what bug you are trying to fix, or why your
patch should be an improvement, we will not install it. A test case will
help us to understand.
</p>
</li><li>
A guess about what the bug is or what it depends on.
<p>Such guesses are usually wrong. Even we cannot guess right about such
things without first using the debugger to find the facts.
</p></li></ul>
<hr size="6">
<a name="History-and-Acknowledgments"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Bug-Reporting" title="Previous section in reading order"> < </a>]</td>
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="History-and-Acknowledgments-1"></a>
<h1 class="chapter">7. History and Acknowledgments</h1>
<p>The suggestion for a debugger for a Bourne-like shell came from the book
“Learning the Korn Shell”, by Bill Rosenblatt Copyright (C) 1993 by
O’Reilly and Associates, Inc. Others such as Cigy Cyriac, Chet Ramey,
Rocky Bernstein, and Gary V. Vaughan expanded and improved on that.
</p>
<p>However Bourne-Shell debuggers rely on a signal mechanism
(<code>SIGDEBUG</code>) to call a debugger routine. In the Korn shell as
well as <small>BASH</small> in versions prior to 2.05, there was a fundamental
flaw: the routine that you registered in the trap, got called
<em>after</em> the statement was executed. It takes little imagination
to realize that this is a bit too late to find and correct errors,
especially if the offending command happens to do serious damage like
remove filesystems or reboot a server. As a horrible hack, these
debuggers added one to the line number that was just executed on the
wishful thinking that this would then be the line of next statement to
execute. Sometimes this was correct, but it was too often wrong, such
as in loops and conditionals, comments, or commands that are continued
on the next line.
</p>
<p>Another failing of these debuggers was the inability to debug into
functions or into sourced files, provide a stack trace, dynamically
skip a statement to be run, unconditionally trace into a function or
subshell, or stop when a subroutine, sourced file, or subshell
completed. In truth, the crux of the problem lay in debugging support
in BASH. Given that there was limited bash debugging support, it is
not surprising that these debuggers could not do any of the things
listed above and could debug only a single shell in a single source
file: lines could be listed only from a single text, breakpoints were
set into the text which was in fact a copy of the script name
prepended with debugger routines.
</p>
<p>In version 2.04 of BASH, Rocky Bernstein started hacking on BASH to
add call-stack information, source file information, allow for
debugging into functions and for reporting line numbers in functions
as relative to the file rather than the beginning of a function whose
origin line number was not accessible from BASH. He started changing
the user commands in bashdb to be like other more-advanced debuggers,
in particular <code>perl5db</code> and <code>gdb</code>. However he gave up on
this project when realizing that stopping before a line was crucial. A
patch for this was nontrivial and wildly changed
semantics. Furthermore the chance of getting his other patches into
BASH was was not going to happen in version 2.04.
</p>
<p>In version 2.05, the fundamental necessary change to the semantics of
<code>SIGDEBUG</code> trap handling (suggested at least two years earlier)
was made. Also, version 2.05 changed the line-number reporting in a
function to be relative to the beginning of the file rather than the
beginning of a function—sometimes. Rocky then picked up where he
left off and this then became this debugger. A complete rewrite of the
debugger, some of which started in 2.04 was undertaken. Debugger
internals were changed to support multiple file names, save and
restore the calling environment (such as variables <code>$1</code> and
<code>$?</code>) and install debugger signal handlers. Work was also done on
the BASH in conjunction with the debugger to save stack trace
information, provide a means for stopping after a routine finished,
debugging into a subshell and so on. And a number of changes were made
to BASH just to improve the accuracy of the line number reporting
which is crucial in a debugger.
</p>
<p>This documentation was modified from the GNU Debugger (GDB) Reference
manual.
</p>
<blockquote><p>Additions to this section are particularly welcome. If you or your
friends (or enemies, to be evenhanded) have been unfairly omitted from
this list, we would like to add your names!
</p></blockquote>
<p>The following have contributed directly or indrectly to bashdb:
</p>
<p>Rocky Bernstein (initial full-featured bashdb with stack tracing and
multi-file support)
</p>
<p>Masatake YAMATO (help to merge Rocky’s hack to the official bash source tree)
</p>
<p>Bill Rosenblatt (kshdb),
Michael Loukides (kshdb),
Cigy Cyriac (proto bashdb),
Chet Ramey (proto bashdb),
and
Gary V. Vaughan (proto bashdb).
</p>
<p>Authors of per5ldb:
</p>
<p>Ray Lischner,
Johan Vromans,
and
Ilya Zakharevich.
</p>
<p>Authors of GDB:
</p>
<p>Richard Stallman,
Andrew Cagney,
Jim Blandy,
Jason Molenda,
Stan Shebs,
Fred Fish,
Stu Grossman,
John Gilmore,
Jim Kingdon,
and
Randy Smith (to name just a few).
</p>
<p>Authors of GUD:
</p>
<p>Eric S. Raymond.
</p>
<hr size="6">
<a name="Copying"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#History-and-Acknowledgments" title="Previous section in reading order"> < </a>]</td>
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</tr></table>
<a name="GNU-GENERAL-PUBLIC-LICENSE"></a>
<h1 class="appendix">A. GNU GENERAL PUBLIC LICENSE</h1>
<p align="center"> Version 2, June 1991
</p>
<table><tr><td> </td><td><pre class="display">Copyright © 1989, 1991 Free Software Foundation, Inc.
59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
On Debian systems the full text of the latest General Public License (GPL) can
be found at /usr/share/common-licenses/GPL.
</pre></td></tr></table>
<hr size="6">
<a name="GNU-Free-Documentation-License"></a>
<table cellpadding="1" cellspacing="1" border="0">
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<a name="GNU-Free-Documentation-License-1"></a>
<h1 class="appendix">B. GNU Free Documentation License</h1>
<p align="center"> Version 1.1, March 2000
</p>
<table><tr><td> </td><td><pre class="display">On Debian systems the full text of the latest Free Documentation License (FDL) can
be found at /usr/share/common-licenses/FDL.
</pre></td></tr></table>
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<h1 class="unnumbered">Function Index</h1>
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<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
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<a name="Command-Index-1"></a>
<h1 class="unnumbered">Command Index</h1>
<table><tr><th valign="top">Jump to: </th><td><a href="#Command-Index-1_ky_symbol-1" class="summary-letter"><b>!</b></a>
<a href="#Command-Index-1_ky_symbol-2" class="summary-letter"><b>#</b></a>
<br>
<a href="#Command-Index-1_ky_letter-A" class="summary-letter"><b>A</b></a>
<a href="#Command-Index-1_ky_letter-B" class="summary-letter"><b>B</b></a>
<a href="#Command-Index-1_ky_letter-C" class="summary-letter"><b>C</b></a>
<a href="#Command-Index-1_ky_letter-D" class="summary-letter"><b>D</b></a>
<a href="#Command-Index-1_ky_letter-E" class="summary-letter"><b>E</b></a>
<a href="#Command-Index-1_ky_letter-F" class="summary-letter"><b>F</b></a>
<a href="#Command-Index-1_ky_letter-H" class="summary-letter"><b>H</b></a>
<a href="#Command-Index-1_ky_letter-I" class="summary-letter"><b>I</b></a>
<a href="#Command-Index-1_ky_letter-K" class="summary-letter"><b>K</b></a>
<a href="#Command-Index-1_ky_letter-L" class="summary-letter"><b>L</b></a>
<a href="#Command-Index-1_ky_letter-N" class="summary-letter"><b>N</b></a>
<a href="#Command-Index-1_ky_letter-P" class="summary-letter"><b>P</b></a>
<a href="#Command-Index-1_ky_letter-Q" class="summary-letter"><b>Q</b></a>
<a href="#Command-Index-1_ky_letter-R" class="summary-letter"><b>R</b></a>
<a href="#Command-Index-1_ky_letter-S" class="summary-letter"><b>S</b></a>
<a href="#Command-Index-1_ky_letter-T" class="summary-letter"><b>T</b></a>
<a href="#Command-Index-1_ky_letter-U" class="summary-letter"><b>U</b></a>
<a href="#Command-Index-1_ky_letter-V" class="summary-letter"><b>V</b></a>
<a href="#Command-Index-1_ky_letter-W" class="summary-letter"><b>W</b></a>
<a href="#Command-Index-1_ky_letter-X" class="summary-letter"><b>X</b></a>
</td></tr></table>
<table border="0" class="index-ky">
<tr><td></td><th align="left">Index Entry</th><th align="left"> Section</th></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Command-Index-1_ky_symbol-1">!</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-_0021_0021-_0028shell_0029"><code>!! <span class="roman">(<code>shell</code>)</span></code></a></td><td valign="top"><a href="#Evaluation_002fExecution">4.11 Running Arbitrary BASH and Shell commands (‘<samp>eval</samp>’, ‘<samp>shell</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_0021_005b_002d_005dn-_0028history_0029"><code>!<span class="roman">[</span>-<span class="roman">]</span><var>n</var> <span class="roman">(<code>history</code>)</span></code></a></td><td valign="top"><a href="#History">4.14.13 Command history (‘<samp>H</samp>’, ‘<samp>history</samp>’, ‘<samp>!</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Command-Index-1_ky_symbol-2">#</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-_0023-_0028a-comment_0029"><code># <span class="roman">(a comment)</span></code></a></td><td valign="top"><a href="#Command-Syntax">4.1 Command syntax</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Command-Index-1_ky_letter-A">A</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-alias-name-command"><code>alias <var>name</var> <var>command</var></code></a></td><td valign="top"><a href="#Alias">4.14.1 Debugger Command Aliases (‘<samp>alias</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Command-Index-1_ky_letter-B">B</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-b-_0028break_0029"><code>b <span class="roman">(<code>break</code>)</span></code></a></td><td valign="top"><a href="#Set-Breaks">4.4.1.1 Setting breakpoints (‘<samp>break</samp>’ ‘<samp>tbreak</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-backtrace"><code>backtrace</code></a></td><td valign="top"><a href="#Backtrace">4.6.2 Backtraces (‘<samp>where</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-break"><code>break</code></a></td><td valign="top"><a href="#Set-Breaks">4.4.1.1 Setting breakpoints (‘<samp>break</samp>’ ‘<samp>tbreak</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-bt-_0028backtrace_0029"><code>bt <span class="roman">(<code>backtrace</code>)</span></code></a></td><td valign="top"><a href="#Backtrace">4.6.2 Backtraces (‘<samp>where</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Command-Index-1_ky_letter-C">C</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-c-_0028continue_0029"><code>c <span class="roman">(<code>continue</code>)</span></code></a></td><td valign="top"><a href="#Continue">4.4.2.5 Continue (‘<samp>continue</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-cd-_005bdirectory_005d"><code>cd <span class="roman">[</span><var>directory</var><span class="roman">]</span></code></a></td><td valign="top"><a href="#Interfacing-to-the-OS">4.12 Interfacing to the OS (‘<samp>cd</samp>’, ‘<samp>pwd</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-clear"><code>clear</code></a></td><td valign="top"><a href="#Delete-Breaks">4.4.1.4 Deleting breakpoints (‘<samp>clear</samp>’, ‘<samp>delete</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-commands"><code>commands</code></a></td><td valign="top"><a href="#Break-Commands">4.4.1.3 Breakpoint command lists (‘<samp>commands</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-condition"><code>condition</code></a></td><td valign="top"><a href="#Conditions">4.4.1.6 Break conditions (‘<samp>condition</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-continue"><code>continue</code></a></td><td valign="top"><a href="#Continue">4.4.2.5 Continue (‘<samp>continue</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Command-Index-1_ky_letter-D">D</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-d-_0028clear_0029"><code>d <span class="roman">(<code>clear</code>)</span></code></a></td><td valign="top"><a href="#Delete-Breaks">4.4.1.4 Deleting breakpoints (‘<samp>clear</samp>’, ‘<samp>delete</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-de-_0028delete_0029"><code>de <span class="roman">(<code>delete</code>)</span></code></a></td><td valign="top"><a href="#Delete-Breaks">4.4.1.4 Deleting breakpoints (‘<samp>clear</samp>’, ‘<samp>delete</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-debug"><code>debug</code></a></td><td valign="top"><a href="#Debug">4.4.2.6 Debug (‘<samp>debug</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-delete"><code>delete</code></a></td><td valign="top"><a href="#Delete-Breaks">4.4.1.4 Deleting breakpoints (‘<samp>clear</samp>’, ‘<samp>delete</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-delete-display"><code>delete display</code></a></td><td valign="top"><a href="#Auto-Display">4.13 Automatic display (‘<samp>display</samp>’, ‘<samp>undisplay</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-dis-_0028disable_0029"><code>dis <span class="roman">(<code>disable</code>)</span></code></a></td><td valign="top"><a href="#Disabling">4.4.1.5 Disabling breakpoints (‘<samp>disable</samp>’, ‘<samp>enable</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-disable"><code>disable</code></a></td><td valign="top"><a href="#Disabling">4.4.1.5 Disabling breakpoints (‘<samp>disable</samp>’, ‘<samp>enable</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-disable-breakpoints"><code>disable breakpoints</code></a></td><td valign="top"><a href="#Disabling">4.4.1.5 Disabling breakpoints (‘<samp>disable</samp>’, ‘<samp>enable</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-disable-display"><code>disable display</code></a></td><td valign="top"><a href="#Auto-Display">4.13 Automatic display (‘<samp>display</samp>’, ‘<samp>undisplay</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-display"><code>display</code></a></td><td valign="top"><a href="#Auto-Display">4.13 Automatic display (‘<samp>display</samp>’, ‘<samp>undisplay</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-do-_0028down_0029"><code>do <span class="roman">(<code>down</code>)</span></code></a></td><td valign="top"><a href="#Selection">4.6.3 Selecting a frame (‘<samp>up</samp>’, ‘<samp>down</samp>’, ‘<samp>frame</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-down"><code>down</code></a></td><td valign="top"><a href="#Selection">4.6.3 Selecting a frame (‘<samp>up</samp>’, ‘<samp>down</samp>’, ‘<samp>frame</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Command-Index-1_ky_letter-E">E</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-e-_0028eval_0029"><code>e <span class="roman">(<code>eval</code>)</span></code></a></td><td valign="top"><a href="#Evaluation_002fExecution">4.11 Running Arbitrary BASH and Shell commands (‘<samp>eval</samp>’, ‘<samp>shell</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-edit-_005bline_002dspecification_005d"><code>edit <span class="roman">[</span><var>line-specification</var><span class="roman">]</span></code></a></td><td valign="top"><a href="#Edit">4.8 Editing Source files (‘<samp>edit</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-enable"><code>enable</code></a></td><td valign="top"><a href="#Disabling">4.4.1.5 Disabling breakpoints (‘<samp>disable</samp>’, ‘<samp>enable</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-enable-breakpoints"><code>enable breakpoints</code></a></td><td valign="top"><a href="#Disabling">4.4.1.5 Disabling breakpoints (‘<samp>disable</samp>’, ‘<samp>enable</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-enable-display"><code>enable display</code></a></td><td valign="top"><a href="#Auto-Display">4.13 Automatic display (‘<samp>display</samp>’, ‘<samp>undisplay</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-end"><code>end</code></a></td><td valign="top"><a href="#Break-Commands">4.4.1.3 Breakpoint command lists (‘<samp>commands</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-eval"><code>eval</code></a></td><td valign="top"><a href="#Evaluation_002fExecution">4.11 Running Arbitrary BASH and Shell commands (‘<samp>eval</samp>’, ‘<samp>shell</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-examine"><code>examine</code></a></td><td valign="top"><a href="#Data">4.10 Examining Data (‘<samp>print</samp>’, ‘<samp>examine</samp>’, ‘<samp>info variables</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Command-Index-1_ky_letter-F">F</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-file"><code>file</code></a></td><td valign="top"><a href="#File">4.14.6 Specifying a Script-File Association (‘<samp>file</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-finish"><code>finish</code></a></td><td valign="top"><a href="#Finish">4.4.2.3 Finish (‘<samp>finish</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-forward"><code>forward</code></a></td><td valign="top"><a href="#Search">4.9 Searching source files (‘<samp>search</samp>’, ‘<samp>reverse</samp>’, ‘<samp>/.../</samp>’, ‘<samp>?..?</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-frame"><code>frame</code></a></td><td valign="top"><a href="#Selection">4.6.3 Selecting a frame (‘<samp>up</samp>’, ‘<samp>down</samp>’, ‘<samp>frame</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Command-Index-1_ky_letter-H">H</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-h-_0028help_0029"><code>h <span class="roman">(<code>help</code>)</span></code></a></td><td valign="top"><a href="#Help">4.2 Getting help (‘<samp>help</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-H-_005bstart_002dnumber-_005bend_002dnumber_005d_005d"><code>H <span class="roman">[</span><var>start-number</var> <span class="roman">[</span><var>end-number</var><span class="roman">]</span><span class="roman">]</span></code></a></td><td valign="top"><a href="#History">4.14.13 Command history (‘<samp>H</samp>’, ‘<samp>history</samp>’, ‘<samp>!</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-handle"><code>handle</code></a></td><td valign="top"><a href="#handle">4.4.3.1 Intercepting Signals (‘<samp>handle</samp>’, ‘<samp>info handle</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-history-_005b_002d_005d_005bn_005d"><code>history <span class="roman">[</span>-<span class="roman">]</span><span class="roman">[</span><var>n</var><span class="roman">]</span></code></a></td><td valign="top"><a href="#History">4.14.13 Command history (‘<samp>H</samp>’, ‘<samp>history</samp>’, ‘<samp>!</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Command-Index-1_ky_letter-I">I</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-i-_0028info_0029"><code>i <span class="roman">(<code>info</code>)</span></code></a></td><td valign="top"><a href="#Help">4.2 Getting help (‘<samp>help</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-info"><code>info</code></a></td><td valign="top"><a href="#Help">4.2 Getting help (‘<samp>help</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-info-args"><code>info args</code></a></td><td valign="top"><a href="#Info">4.5.1 Showing information about the program being debugged (‘<samp>info</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-info-breakpoints"><code>info breakpoints</code></a></td><td valign="top"><a href="#Set-Breaks">4.4.1.1 Setting breakpoints (‘<samp>break</samp>’ ‘<samp>tbreak</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-info-breakpoints-1"><code>info breakpoints</code></a></td><td valign="top"><a href="#Info">4.5.1 Showing information about the program being debugged (‘<samp>info</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-info-display"><code>info display</code></a></td><td valign="top"><a href="#Info">4.5.1 Showing information about the program being debugged (‘<samp>info</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-info-display-1"><code>info display</code></a></td><td valign="top"><a href="#Auto-Display">4.13 Automatic display (‘<samp>display</samp>’, ‘<samp>undisplay</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-info-files"><code>info files</code></a></td><td valign="top"><a href="#Info">4.5.1 Showing information about the program being debugged (‘<samp>info</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-info-functions"><code>info functions</code></a></td><td valign="top"><a href="#Info">4.5.1 Showing information about the program being debugged (‘<samp>info</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-info-line"><code>info line</code></a></td><td valign="top"><a href="#Info">4.5.1 Showing information about the program being debugged (‘<samp>info</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-info-program"><code>info program</code></a></td><td valign="top"><a href="#Info">4.5.1 Showing information about the program being debugged (‘<samp>info</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-info-signals"><code>info signals</code></a></td><td valign="top"><a href="#handle">4.4.3.1 Intercepting Signals (‘<samp>handle</samp>’, ‘<samp>info handle</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-info-signals-1"><code>info signals</code></a></td><td valign="top"><a href="#Info">4.5.1 Showing information about the program being debugged (‘<samp>info</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-info-source"><code>info source</code></a></td><td valign="top"><a href="#Info">4.5.1 Showing information about the program being debugged (‘<samp>info</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-info-stack"><code>info stack</code></a></td><td valign="top"><a href="#Info">4.5.1 Showing information about the program being debugged (‘<samp>info</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-info-terminal"><code>info terminal</code></a></td><td valign="top"><a href="#Input_002fOutput">3.4 Your script’s input and output</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-info-terminal-1"><code>info terminal</code></a></td><td valign="top"><a href="#Info">4.5.1 Showing information about the program being debugged (‘<samp>info</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-info-variables"><code>info variables</code></a></td><td valign="top"><a href="#Info">4.5.1 Showing information about the program being debugged (‘<samp>info</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-info-variables-1"><code>info variables</code></a></td><td valign="top"><a href="#Data">4.10 Examining Data (‘<samp>print</samp>’, ‘<samp>examine</samp>’, ‘<samp>info variables</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Command-Index-1_ky_letter-K">K</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-k-_0028kill_0029"><code>k <span class="roman">(<code>kill</code>)</span></code></a></td><td valign="top"><a href="#Quit">4.3 Quitting the BASH debugger (‘<samp>quit</samp>’, ‘<samp>kill</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Command-Index-1_ky_letter-L">L</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-l-_0028list_0029"><code>l <span class="roman">(<code>list</code>)</span></code></a></td><td valign="top"><a href="#List">4.7 Examining Source Files (‘<samp>list</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-list"><code>list</code></a></td><td valign="top"><a href="#List">4.7 Examining Source Files (‘<samp>list</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Command-Index-1_ky_letter-N">N</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-n-_0028next_0029"><code>n <span class="roman">(<code>next</code>)</span></code></a></td><td valign="top"><a href="#Next">4.4.2.2 Next (‘<samp>next</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-next"><code>next</code></a></td><td valign="top"><a href="#Next">4.4.2.2 Next (‘<samp>next</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Command-Index-1_ky_letter-P">P</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-p-_0028print_0029"><code>p <span class="roman">(<code>print</code>)</span></code></a></td><td valign="top"><a href="#Data">4.10 Examining Data (‘<samp>print</samp>’, ‘<samp>examine</samp>’, ‘<samp>info variables</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-print"><code>print</code></a></td><td valign="top"><a href="#Data">4.10 Examining Data (‘<samp>print</samp>’, ‘<samp>examine</samp>’, ‘<samp>info variables</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-print-1"><code>print</code></a></td><td valign="top"><a href="#Data">4.10 Examining Data (‘<samp>print</samp>’, ‘<samp>examine</samp>’, ‘<samp>info variables</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-pwd"><code>pwd</code></a></td><td valign="top"><a href="#Interfacing-to-the-OS">4.12 Interfacing to the OS (‘<samp>cd</samp>’, ‘<samp>pwd</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Command-Index-1_ky_letter-Q">Q</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-q-_0028quit_0029"><code>q <span class="roman">(<code>quit</code>)</span></code></a></td><td valign="top"><a href="#Quit">4.3 Quitting the BASH debugger (‘<samp>quit</samp>’, ‘<samp>kill</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-quit-_005bexpression-_005bsubshell_002dlevels_005d_005d"><code>quit <span class="roman">[</span><var>expression</var> <span class="roman">[</span><var>subshell-levels</var><span class="roman">]</span><span class="roman">]</span></code></a></td><td valign="top"><a href="#Quit">4.3 Quitting the BASH debugger (‘<samp>quit</samp>’, ‘<samp>kill</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Command-Index-1_ky_letter-R">R</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-R-_0028restart_0029"><code>R <span class="roman">(<code>restart</code>)</span></code></a></td><td valign="top"><a href="#Starting">3.1 Starting your script</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-restart-_005bargs_005d"><code>restart <span class="roman">[</span><var>args</var><span class="roman">]</span></code></a></td><td valign="top"><a href="#Starting">3.1 Starting your script</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-RET-_0028repeat-last-command_0029"><code>RET <span class="roman">(repeat last command)</span></code></a></td><td valign="top"><a href="#Command-Syntax">4.1 Command syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-return"><code>return</code></a></td><td valign="top"><a href="#Returning">4.4.2.7 Returning from a function, sourced file, or subshell (‘<samp>return</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-reverse_002dsearch"><code>reverse-search</code></a></td><td valign="top"><a href="#Search">4.9 Searching source files (‘<samp>search</samp>’, ‘<samp>reverse</samp>’, ‘<samp>/.../</samp>’, ‘<samp>?..?</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-run-_0028restart_0029"><code>run <span class="roman">(<code>restart</code>)</span></code></a></td><td valign="top"><a href="#Starting">3.1 Starting your script</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Command-Index-1_ky_letter-S">S</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-s-_0028step_0029"><code>s <span class="roman">(<code>step</code>)</span></code></a></td><td valign="top"><a href="#Step">4.4.2.1 Step (‘<samp>step</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-search"><code>search</code></a></td><td valign="top"><a href="#Search">4.9 Searching source files (‘<samp>search</samp>’, ‘<samp>reverse</samp>’, ‘<samp>/.../</samp>’, ‘<samp>?..?</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-set-annotate"><code>set annotate</code></a></td><td valign="top"><a href="#Annotate">4.14.2 Annotation Level (‘<samp>set annotate</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-set-args"><code>set args</code></a></td><td valign="top"><a href="#Arguments">3.3 Your script’s arguments</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-set-autoeval-_005b-on-_007c-1-_007c-off-_007c-0-_005d"><code>set autoeval <span class="roman">[</span> on | 1 | off | 0 <span class="roman">]</span></code></a></td><td valign="top"><a href="#Autoeval">4.14.3 Set/Show auto-eval (‘<samp>set autoeval</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-set-basename"><code>set basename</code></a></td><td valign="top"><a href="#Basename">4.14.4 File basename (‘<samp>set basename</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-set-debugger"><code>set debugger</code></a></td><td valign="top"><a href="#Debugger">4.14.5 Allow Debugging the debugger (‘<samp>set debugger</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-set-editing"><code>set editing</code></a></td><td valign="top"><a href="#Editing">4.14.10 Command editing (‘<samp>set editing</samp>’, ‘<samp>show editing</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-set-history-save"><code>set history save</code></a></td><td valign="top"><a href="#History">4.14.13 Command history (‘<samp>H</samp>’, ‘<samp>history</samp>’, ‘<samp>!</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-set-history-size"><code>set history size</code></a></td><td valign="top"><a href="#History">4.14.13 Command history (‘<samp>H</samp>’, ‘<samp>history</samp>’, ‘<samp>!</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-set-linetrace"><code>set linetrace</code></a></td><td valign="top"><a href="#Line-Tracing">4.14.7 Show position information as statements are executed (‘<samp>set linetrace</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-set-listsize"><code>set listsize</code></a></td><td valign="top"><a href="#List">4.7 Examining Source Files (‘<samp>list</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-set-logging"><code>set logging</code></a></td><td valign="top"><a href="#Logging">4.14.8 Logging output (‘<samp>set logging</samp>’, ‘<samp>set logging file</samp>’...)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-set-prompt"><code>set prompt</code></a></td><td valign="top"><a href="#Prompt">4.14.9 Prompt (‘<samp>set prompt</samp>’, ‘<samp>show prompt</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-set-showcommand"><code>set showcommand</code></a></td><td valign="top"><a href="#Command-Display">4.14.12 Command Display (‘<samp>set showcommand</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-set-trace_002dcommands"><code>set trace-commands</code></a></td><td valign="top"><a href="#Command_002dTracing">4.14.11 Debugger Commands Tracing (‘<samp>set trace-commands</samp>’, ‘<samp>show trace-commands</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-shell"><code>shell</code></a></td><td valign="top"><a href="#Evaluation_002fExecution">4.11 Running Arbitrary BASH and Shell commands (‘<samp>eval</samp>’, ‘<samp>shell</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-show-args"><code>show args</code></a></td><td valign="top"><a href="#Arguments">3.3 Your script’s arguments</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-show-autoeval"><code>show autoeval</code></a></td><td valign="top"><a href="#Autoeval">4.14.3 Set/Show auto-eval (‘<samp>set autoeval</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-show-copying"><code>show copying</code></a></td><td valign="top"><a href="#Show">4.5.2 Show information about the debugger (‘<samp>show</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-show-editing"><code>show editing</code></a></td><td valign="top"><a href="#Editing">4.14.10 Command editing (‘<samp>set editing</samp>’, ‘<samp>show editing</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-show-history"><code>show history</code></a></td><td valign="top"><a href="#History">4.14.13 Command history (‘<samp>H</samp>’, ‘<samp>history</samp>’, ‘<samp>!</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-show-listsize"><code>show listsize</code></a></td><td valign="top"><a href="#List">4.7 Examining Source Files (‘<samp>list</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-show-prompt"><code>show prompt</code></a></td><td valign="top"><a href="#Prompt">4.14.9 Prompt (‘<samp>set prompt</samp>’, ‘<samp>show prompt</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-show-version"><code>show version</code></a></td><td valign="top"><a href="#Show">4.5.2 Show information about the debugger (‘<samp>show</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-show-warranty"><code>show warranty</code></a></td><td valign="top"><a href="#Show">4.5.2 Show information about the debugger (‘<samp>show</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-shows"><code>shows</code></a></td><td valign="top"><a href="#History">4.14.13 Command history (‘<samp>H</samp>’, ‘<samp>history</samp>’, ‘<samp>!</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-signal"><code>signal</code></a></td><td valign="top"><a href="#signal">4.4.3.2 Sending your program a signal (‘<samp>signal</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-silent"><code>silent</code></a></td><td valign="top"><a href="#Break-Commands">4.4.1.3 Breakpoint command lists (‘<samp>commands</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-skip"><code>skip</code></a></td><td valign="top"><a href="#Skip">4.4.2.4 Skip (‘<samp>skip</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-source"><code>source</code></a></td><td valign="top"><a href="#Command-Files">3.2 Command files</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-step"><code>step</code></a></td><td valign="top"><a href="#Step">4.4.2.1 Step (‘<samp>step</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Command-Index-1_ky_letter-T">T</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-tbreak"><code>tbreak</code></a></td><td valign="top"><a href="#Set-Breaks">4.4.1.1 Setting breakpoints (‘<samp>break</samp>’ ‘<samp>tbreak</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-tty"><code>tty</code></a></td><td valign="top"><a href="#Input_002fOutput">3.4 Your script’s input and output</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Command-Index-1_ky_letter-U">U</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-unalias-name-command"><code>unalias <var>name</var> <var>command</var></code></a></td><td valign="top"><a href="#Alias">4.14.1 Debugger Command Aliases (‘<samp>alias</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-undisplay-dnums_2026"><code>undisplay <var>dnums</var>…</code></a></td><td valign="top"><a href="#Auto-Display">4.13 Automatic display (‘<samp>display</samp>’, ‘<samp>undisplay</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-up-_005bn_005d"><code>up <span class="roman">[</span><var>n</var><span class="roman">]</span></code></a></td><td valign="top"><a href="#Selection">4.6.3 Selecting a frame (‘<samp>up</samp>’, ‘<samp>down</samp>’, ‘<samp>frame</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Command-Index-1_ky_letter-V">V</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-V-_0028info-variables_0029"><code>V <span class="roman">(<code>info variables</code>)</span></code></a></td><td valign="top"><a href="#Data">4.10 Examining Data (‘<samp>print</samp>’, ‘<samp>examine</samp>’, ‘<samp>info variables</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Command-Index-1_ky_letter-W">W</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-watch"><code>watch</code></a></td><td valign="top"><a href="#Set-Watchpoints">4.4.1.2 Setting watchpoints (‘<samp>watch</samp>’, ‘<samp>watche</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-where"><code>where</code></a></td><td valign="top"><a href="#Backtrace">4.6.2 Backtraces (‘<samp>where</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Command-Index-1_ky_letter-X">X</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-x-_0028examine_0029"><code>x <span class="roman">(<code>examine</code>)</span></code></a></td><td valign="top"><a href="#Data">4.10 Examining Data (‘<samp>print</samp>’, ‘<samp>examine</samp>’, ‘<samp>info variables</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
</table>
<table><tr><th valign="top">Jump to: </th><td><a href="#Command-Index-1_ky_symbol-1" class="summary-letter"><b>!</b></a>
<a href="#Command-Index-1_ky_symbol-2" class="summary-letter"><b>#</b></a>
<br>
<a href="#Command-Index-1_ky_letter-A" class="summary-letter"><b>A</b></a>
<a href="#Command-Index-1_ky_letter-B" class="summary-letter"><b>B</b></a>
<a href="#Command-Index-1_ky_letter-C" class="summary-letter"><b>C</b></a>
<a href="#Command-Index-1_ky_letter-D" class="summary-letter"><b>D</b></a>
<a href="#Command-Index-1_ky_letter-E" class="summary-letter"><b>E</b></a>
<a href="#Command-Index-1_ky_letter-F" class="summary-letter"><b>F</b></a>
<a href="#Command-Index-1_ky_letter-H" class="summary-letter"><b>H</b></a>
<a href="#Command-Index-1_ky_letter-I" class="summary-letter"><b>I</b></a>
<a href="#Command-Index-1_ky_letter-K" class="summary-letter"><b>K</b></a>
<a href="#Command-Index-1_ky_letter-L" class="summary-letter"><b>L</b></a>
<a href="#Command-Index-1_ky_letter-N" class="summary-letter"><b>N</b></a>
<a href="#Command-Index-1_ky_letter-P" class="summary-letter"><b>P</b></a>
<a href="#Command-Index-1_ky_letter-Q" class="summary-letter"><b>Q</b></a>
<a href="#Command-Index-1_ky_letter-R" class="summary-letter"><b>R</b></a>
<a href="#Command-Index-1_ky_letter-S" class="summary-letter"><b>S</b></a>
<a href="#Command-Index-1_ky_letter-T" class="summary-letter"><b>T</b></a>
<a href="#Command-Index-1_ky_letter-U" class="summary-letter"><b>U</b></a>
<a href="#Command-Index-1_ky_letter-V" class="summary-letter"><b>V</b></a>
<a href="#Command-Index-1_ky_letter-W" class="summary-letter"><b>W</b></a>
<a href="#Command-Index-1_ky_letter-X" class="summary-letter"><b>X</b></a>
</td></tr></table>
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<td valign="middle" align="left">[<a href="#Function-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
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<a name="Variable-Index-1"></a>
<h1 class="unnumbered">Variable Index</h1>
<hr size="6">
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<table cellpadding="1" cellspacing="1" border="0">
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<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Function-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
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<a name="General-Index-1"></a>
<h1 class="unnumbered">General Index</h1>
<table><tr><th valign="top">Jump to: </th><td><a href="#General-Index-1_cp_symbol-1" class="summary-letter"><b>$</b></a>
<a href="#General-Index-1_cp_symbol-2" class="summary-letter"><b>-</b></a>
<a href="#General-Index-1_cp_symbol-3" class="summary-letter"><b>.</b></a>
<br>
<a href="#General-Index-1_cp_letter-A" class="summary-letter"><b>A</b></a>
<a href="#General-Index-1_cp_letter-B" class="summary-letter"><b>B</b></a>
<a href="#General-Index-1_cp_letter-C" class="summary-letter"><b>C</b></a>
<a href="#General-Index-1_cp_letter-D" class="summary-letter"><b>D</b></a>
<a href="#General-Index-1_cp_letter-E" class="summary-letter"><b>E</b></a>
<a href="#General-Index-1_cp_letter-F" class="summary-letter"><b>F</b></a>
<a href="#General-Index-1_cp_letter-G" class="summary-letter"><b>G</b></a>
<a href="#General-Index-1_cp_letter-H" class="summary-letter"><b>H</b></a>
<a href="#General-Index-1_cp_letter-I" class="summary-letter"><b>I</b></a>
<a href="#General-Index-1_cp_letter-L" class="summary-letter"><b>L</b></a>
<a href="#General-Index-1_cp_letter-N" class="summary-letter"><b>N</b></a>
<a href="#General-Index-1_cp_letter-O" class="summary-letter"><b>O</b></a>
<a href="#General-Index-1_cp_letter-P" class="summary-letter"><b>P</b></a>
<a href="#General-Index-1_cp_letter-R" class="summary-letter"><b>R</b></a>
<a href="#General-Index-1_cp_letter-S" class="summary-letter"><b>S</b></a>
<a href="#General-Index-1_cp_letter-T" class="summary-letter"><b>T</b></a>
<a href="#General-Index-1_cp_letter-V" class="summary-letter"><b>V</b></a>
<a href="#General-Index-1_cp_letter-W" class="summary-letter"><b>W</b></a>
</td></tr></table>
<table border="0" class="index-cp">
<tr><td></td><th align="left">Index Entry</th><th align="left"> Section</th></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="General-Index-1_cp_symbol-1">$</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-_0024PS4"><code>$PS4</code></a></td><td valign="top"><a href="#Interactive-Line-Tracing-Session">1.2 Interactive Line Tracing Session</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_0024_005f-and-info-breakpoints"><code>$_</code> and <code>info breakpoints</code></a></td><td valign="top"><a href="#Set-Breaks">4.4.1.1 Setting breakpoints (‘<samp>break</samp>’ ‘<samp>tbreak</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="General-Index-1_cp_symbol-2">-</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-_002d_002dannotate"><code>--annotate</code></a></td><td valign="top"><a href="#Options-for-the-bashdb-script">2.1.1 Command-line options for <code>bashdb</code> script</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_002d_002dbasename"><code>--basename</code></a></td><td valign="top"><a href="#Options-for-the-bashdb-script">2.1.1 Command-line options for <code>bashdb</code> script</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_002d_002dcommand"><code>--command</code></a></td><td valign="top"><a href="#Options-for-the-bashdb-script">2.1.1 Command-line options for <code>bashdb</code> script</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_002d_002deval_002dcommand-cmdfile"><code>--eval-command</code> <var>cmdfile</var></a></td><td valign="top"><a href="#Options-for-the-bashdb-script">2.1.1 Command-line options for <code>bashdb</code> script</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_002d_002dhelp"><code>--help</code></a></td><td valign="top"><a href="#Options-for-the-bashdb-script">2.1.1 Command-line options for <code>bashdb</code> script</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_002d_002dlibrary"><code>--library</code></a></td><td valign="top"><a href="#Options-for-the-bashdb-script">2.1.1 Command-line options for <code>bashdb</code> script</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_002d_002dno_002dinit"><code>--no-init</code></a></td><td valign="top"><a href="#Options-for-the-bashdb-script">2.1.1 Command-line options for <code>bashdb</code> script</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_002d_002dnx"><code>--nx</code></a></td><td valign="top"><a href="#Options-for-the-bashdb-script">2.1.1 Command-line options for <code>bashdb</code> script</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_002d_002dquiet"><code>--quiet</code></a></td><td valign="top"><a href="#Options-for-the-bashdb-script">2.1.1 Command-line options for <code>bashdb</code> script</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_002d_002dtempdir"><code>--tempdir</code></a></td><td valign="top"><a href="#Options-for-the-bashdb-script">2.1.1 Command-line options for <code>bashdb</code> script</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_002d_002dterminal"><code>--terminal</code></a></td><td valign="top"><a href="#Options-for-the-bashdb-script">2.1.1 Command-line options for <code>bashdb</code> script</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_002d_002dtty"><code>--tty</code></a></td><td valign="top"><a href="#Options-for-the-bashdb-script">2.1.1 Command-line options for <code>bashdb</code> script</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_002dA"><code>-A</code></a></td><td valign="top"><a href="#Options-for-the-bashdb-script">2.1.1 Command-line options for <code>bashdb</code> script</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_002dB"><code>-B</code></a></td><td valign="top"><a href="#Options-for-the-bashdb-script">2.1.1 Command-line options for <code>bashdb</code> script</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_002dc"><code>-c</code></a></td><td valign="top"><a href="#Options-for-the-bashdb-script">2.1.1 Command-line options for <code>bashdb</code> script</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_002dh"><code>-h</code></a></td><td valign="top"><a href="#Options-for-the-bashdb-script">2.1.1 Command-line options for <code>bashdb</code> script</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_002dL"><code>-L</code></a></td><td valign="top"><a href="#Options-for-the-bashdb-script">2.1.1 Command-line options for <code>bashdb</code> script</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_002dn"><code>-n</code></a></td><td valign="top"><a href="#Options-for-the-bashdb-script">2.1.1 Command-line options for <code>bashdb</code> script</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_002dq"><code>-q</code></a></td><td valign="top"><a href="#Options-for-the-bashdb-script">2.1.1 Command-line options for <code>bashdb</code> script</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_002dT"><code>-T</code></a></td><td valign="top"><a href="#Options-for-the-bashdb-script">2.1.1 Command-line options for <code>bashdb</code> script</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_002dt"><code>-t</code></a></td><td valign="top"><a href="#Options-for-the-bashdb-script">2.1.1 Command-line options for <code>bashdb</code> script</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_002dV"><code>-V</code></a></td><td valign="top"><a href="#Options-for-the-bashdb-script">2.1.1 Command-line options for <code>bashdb</code> script</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_002dx"><code>-x</code></a></td><td valign="top"><a href="#Options-for-the-bashdb-script">2.1.1 Command-line options for <code>bashdb</code> script</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="General-Index-1_cp_symbol-3">.</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-_002ebashdbinit">‘<tt>.bashdbinit</tt>’</a></td><td valign="top"><a href="#Command-Files">3.2 Command files</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="General-Index-1_cp_letter-A">A</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-arguments-_0028to-your-script_0029">arguments (to your script)</a></td><td valign="top"><a href="#Arguments">3.3 Your script’s arguments</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-automatic-display">automatic display</a></td><td valign="top"><a href="#Auto-Display">4.13 Automatic display (‘<samp>display</samp>’, ‘<samp>undisplay</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="General-Index-1_cp_letter-B">B</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-backtraces">backtraces</a></td><td valign="top"><a href="#Backtrace">4.6.2 Backtraces (‘<samp>where</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-BASH-debugger-bugs_002c-reporting">BASH debugger bugs, reporting</a></td><td valign="top"><a href="#Bug-Reporting">6.2 How to report bugs</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-bashdb_002eini">‘<tt>bashdb.ini</tt>’</a></td><td valign="top"><a href="#Command-Files">3.2 Command files</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-breakpoint-conditions">breakpoint conditions</a></td><td valign="top"><a href="#Conditions">4.4.1.6 Break conditions (‘<samp>condition</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-breakpoint-numbers">breakpoint numbers</a></td><td valign="top"><a href="#Breakpoints">4.4.1 Breakpoints, watchpoints (‘<samp>break</samp>’, ‘<samp>tbreak</samp>’, ‘<samp>watch</samp>’, ‘<samp>watche</samp>’...)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-breakpoint-on-variable-modification">breakpoint on variable modification</a></td><td valign="top"><a href="#Breakpoints">4.4.1 Breakpoints, watchpoints (‘<samp>break</samp>’, ‘<samp>tbreak</samp>’, ‘<samp>watch</samp>’, ‘<samp>watche</samp>’...)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-breakpoints">breakpoints</a></td><td valign="top"><a href="#Breakpoints">4.4.1 Breakpoints, watchpoints (‘<samp>break</samp>’, ‘<samp>tbreak</samp>’, ‘<samp>watch</samp>’, ‘<samp>watche</samp>’...)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-bug-criteria">bug criteria</a></td><td valign="top"><a href="#Bug-Criteria">6.1 Have you found a bug?</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-bug-reports">bug reports</a></td><td valign="top"><a href="#Bug-Reporting">6.2 How to report bugs</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-bugs">bugs</a></td><td valign="top"><a href="#BASH-Debugger-Bugs">6. Reporting Bugs</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="General-Index-1_cp_letter-C">C</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-call-stack">call stack</a></td><td valign="top"><a href="#Stack">4.6 Examining the Stack Frame (‘<samp>where</samp>’, ‘<samp>frame</samp>’, ‘<samp>up</samp>’, ‘<samp>down</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-change-working-directory">change working directory</a></td><td valign="top"><a href="#Interfacing-to-the-OS">4.12 Interfacing to the OS (‘<samp>cd</samp>’, ‘<samp>pwd</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-clearing-breakpoints_002c-watchpoints">clearing breakpoints, watchpoints</a></td><td valign="top"><a href="#Delete-Breaks">4.4.1.4 Deleting breakpoints (‘<samp>clear</samp>’, ‘<samp>delete</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-command-files">command files</a></td><td valign="top"><a href="#Command-Files">3.2 Command files</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-command-line-editing">command line editing</a></td><td valign="top"><a href="#Editing">4.14.10 Command editing (‘<samp>set editing</samp>’, ‘<samp>show editing</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-command-scripts_002c-debugging">command scripts, debugging</a></td><td valign="top"><a href="#Command_002dTracing">4.14.11 Debugger Commands Tracing (‘<samp>set trace-commands</samp>’, ‘<samp>show trace-commands</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-comment">comment</a></td><td valign="top"><a href="#Command-Syntax">4.1 Command syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-conditional-breakpoints">conditional breakpoints</a></td><td valign="top"><a href="#Conditions">4.4.1.6 Break conditions (‘<samp>condition</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-continuing">continuing</a></td><td valign="top"><a href="#Resuming-Execution">4.4.2 Resuming Execution (‘<samp>step</samp>’, ‘<samp>next</samp>’, ‘<samp>finish</samp>’, ‘<samp>skip</samp>’, ‘<samp>continue</samp>’, ‘<samp>debug</samp>’, ‘<samp>return</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-controlling-terminal">controlling terminal</a></td><td valign="top"><a href="#Input_002fOutput">3.4 Your script’s input and output</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-crash-of-debugger">crash of debugger</a></td><td valign="top"><a href="#Bug-Criteria">6.1 Have you found a bug?</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-current-stack-frame">current stack frame</a></td><td valign="top"><a href="#Selection">4.6.3 Selecting a frame (‘<samp>up</samp>’, ‘<samp>down</samp>’, ‘<samp>frame</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="General-Index-1_cp_letter-D">D</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-DDD">DDD</a></td><td valign="top"><a href="#DDD">5.2 Using the <acronym>BASH</acronym> debugger from <acronym>DDD</acronym></a></td></tr>
<tr><td></td><td valign="top"><a href="#index-debugger-crash">debugger crash</a></td><td valign="top"><a href="#Bug-Criteria">6.1 Have you found a bug?</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-delete-breakpoints">delete breakpoints</a></td><td valign="top"><a href="#Delete-Breaks">4.4.1.4 Deleting breakpoints (‘<samp>clear</samp>’, ‘<samp>delete</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-deleting-breakpoints_002c-watchpoints">deleting breakpoints, watchpoints</a></td><td valign="top"><a href="#Delete-Breaks">4.4.1.4 Deleting breakpoints (‘<samp>clear</samp>’, ‘<samp>delete</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-display-of-expressions">display of expressions</a></td><td valign="top"><a href="#Auto-Display">4.13 Automatic display (‘<samp>display</samp>’, ‘<samp>undisplay</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="General-Index-1_cp_letter-E">E</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-editing">editing</a></td><td valign="top"><a href="#Editing">4.14.10 Command editing (‘<samp>set editing</samp>’, ‘<samp>show editing</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-Emacs">Emacs</a></td><td valign="top"><a href="#Emacs">5.1 Using the <acronym>BASH</acronym> debugger from <small>GNU</small> Emacs</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-error-on-valid-input">error on valid input</a></td><td valign="top"><a href="#Bug-Criteria">6.1 Have you found a bug?</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-examining-data">examining data</a></td><td valign="top"><a href="#Data">4.10 Examining Data (‘<samp>print</samp>’, ‘<samp>examine</samp>’, ‘<samp>info variables</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="General-Index-1_cp_letter-F">F</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-fatal-signal">fatal signal</a></td><td valign="top"><a href="#Bug-Criteria">6.1 Have you found a bug?</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-fatal-signals">fatal signals</a></td><td valign="top"><a href="#Signals">4.4.3 Signals (‘<samp>handle</samp>’, ‘<samp>info handle</samp>’, ‘<samp>signal</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-frame-number">frame number</a></td><td valign="top"><a href="#Frames">4.6.1 Stack frames</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-frame_002c-definition">frame, definition</a></td><td valign="top"><a href="#Frames">4.6.1 Stack frames</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="General-Index-1_cp_letter-G">G</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-GNU-Emacs"><small>GNU</small> Emacs</a></td><td valign="top"><a href="#Emacs">5.1 Using the <acronym>BASH</acronym> debugger from <small>GNU</small> Emacs</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="General-Index-1_cp_letter-H">H</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-handling-signals">handling signals</a></td><td valign="top"><a href="#Signals">4.4.3 Signals (‘<samp>handle</samp>’, ‘<samp>info handle</samp>’, ‘<samp>signal</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-history-save">history save</a></td><td valign="top"><a href="#History">4.14.13 Command history (‘<samp>H</samp>’, ‘<samp>history</samp>’, ‘<samp>!</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-history-size">history size</a></td><td valign="top"><a href="#History">4.14.13 Command history (‘<samp>H</samp>’, ‘<samp>history</samp>’, ‘<samp>!</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="General-Index-1_cp_letter-I">I</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-I_002fO">I/O</a></td><td valign="top"><a href="#Input_002fOutput">3.4 Your script’s input and output</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-init-file">init file</a></td><td valign="top"><a href="#Command-Files">3.2 Command files</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-init-file-name">init file name</a></td><td valign="top"><a href="#Command-Files">3.2 Command files</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-initial-frame">initial frame</a></td><td valign="top"><a href="#Frames">4.6.1 Stack frames</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-innermost-frame">innermost frame</a></td><td valign="top"><a href="#Frames">4.6.1 Stack frames</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-interrupt">interrupt</a></td><td valign="top"><a href="#Quitting-the-BASH-debugger">2.2 Quitting the BASH debugger</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-invalid-input">invalid input</a></td><td valign="top"><a href="#Bug-Criteria">6.1 Have you found a bug?</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="General-Index-1_cp_letter-L">L</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-latest-breakpoint">latest breakpoint</a></td><td valign="top"><a href="#Set-Breaks">4.4.1.1 Setting breakpoints (‘<samp>break</samp>’ ‘<samp>tbreak</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-linespec">linespec</a></td><td valign="top"><a href="#List">4.7 Examining Source Files (‘<samp>list</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="General-Index-1_cp_letter-N">N</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-numbers-for-breakpoints">numbers for breakpoints</a></td><td valign="top"><a href="#Breakpoints">4.4.1 Breakpoints, watchpoints (‘<samp>break</samp>’, ‘<samp>tbreak</samp>’, ‘<samp>watch</samp>’, ‘<samp>watche</samp>’...)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-numbers-for-watchpoints">numbers for watchpoints</a></td><td valign="top"><a href="#Breakpoints">4.4.1 Breakpoints, watchpoints (‘<samp>break</samp>’, ‘<samp>tbreak</samp>’, ‘<samp>watch</samp>’, ‘<samp>watche</samp>’...)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="General-Index-1_cp_letter-O">O</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-one_002dtime-breakpoints">one-time breakpoints</a></td><td valign="top"><a href="#Conditions">4.4.1.6 Break conditions (‘<samp>condition</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-online-documentation">online documentation</a></td><td valign="top"><a href="#Help">4.2 Getting help (‘<samp>help</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-outermost-frame">outermost frame</a></td><td valign="top"><a href="#Frames">4.6.1 Stack frames</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="General-Index-1_cp_letter-P">P</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-print-working-directory">print working directory</a></td><td valign="top"><a href="#Interfacing-to-the-OS">4.12 Interfacing to the OS (‘<samp>cd</samp>’, ‘<samp>pwd</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-printing-data">printing data</a></td><td valign="top"><a href="#Data">4.10 Examining Data (‘<samp>print</samp>’, ‘<samp>examine</samp>’, ‘<samp>info variables</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-prompt">prompt</a></td><td valign="top"><a href="#Prompt">4.14.9 Prompt (‘<samp>set prompt</samp>’, ‘<samp>show prompt</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="General-Index-1_cp_letter-R">R</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-readline">readline</a></td><td valign="top"><a href="#Editing">4.14.10 Command editing (‘<samp>set editing</samp>’, ‘<samp>show editing</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-redirection">redirection</a></td><td valign="top"><a href="#Input_002fOutput">3.4 Your script’s input and output</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-repeating-next_002fstep-commands">repeating next/step commands</a></td><td valign="top"><a href="#Command-Syntax">4.1 Command syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-reporting-bugs">reporting bugs</a></td><td valign="top"><a href="#BASH-Debugger-Bugs">6. Reporting Bugs</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-resuming-execution">resuming execution</a></td><td valign="top"><a href="#Resuming-Execution">4.4.2 Resuming Execution (‘<samp>step</samp>’, ‘<samp>next</samp>’, ‘<samp>finish</samp>’, ‘<samp>skip</samp>’, ‘<samp>continue</samp>’, ‘<samp>debug</samp>’, ‘<samp>return</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-returning-from-a-function_002c-sourced-file-or-subshell">returning from a function, sourced file or subshell</a></td><td valign="top"><a href="#Returning">4.4.2.7 Returning from a function, sourced file, or subshell (‘<samp>return</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-running">running</a></td><td valign="top"><a href="#Starting">3.1 Starting your script</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="General-Index-1_cp_letter-S">S</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-searching">searching</a></td><td valign="top"><a href="#Search">4.9 Searching source files (‘<samp>search</samp>’, ‘<samp>reverse</samp>’, ‘<samp>/.../</samp>’, ‘<samp>?..?</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-selected-frame">selected frame</a></td><td valign="top"><a href="#Stack">4.6 Examining the Stack Frame (‘<samp>where</samp>’, ‘<samp>frame</samp>’, ‘<samp>up</samp>’, ‘<samp>down</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-setting-watchpoints">setting watchpoints</a></td><td valign="top"><a href="#Set-Watchpoints">4.4.1.2 Setting watchpoints (‘<samp>watch</samp>’, ‘<samp>watche</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-shell-escape">shell escape</a></td><td valign="top"><a href="#Evaluation_002fExecution">4.11 Running Arbitrary BASH and Shell commands (‘<samp>eval</samp>’, ‘<samp>shell</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-signals">signals</a></td><td valign="top"><a href="#Signals">4.4.3 Signals (‘<samp>handle</samp>’, ‘<samp>info handle</samp>’, ‘<samp>signal</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-stack-frame">stack frame</a></td><td valign="top"><a href="#Frames">4.6.1 Stack frames</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-stack-traces">stack traces</a></td><td valign="top"><a href="#Backtrace">4.6.2 Backtraces (‘<samp>where</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-starting">starting</a></td><td valign="top"><a href="#Starting">3.1 Starting your script</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-stepping">stepping</a></td><td valign="top"><a href="#Resuming-Execution">4.4.2 Resuming Execution (‘<samp>step</samp>’, ‘<samp>next</samp>’, ‘<samp>finish</samp>’, ‘<samp>skip</samp>’, ‘<samp>continue</samp>’, ‘<samp>debug</samp>’, ‘<samp>return</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="General-Index-1_cp_letter-T">T</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-terminal">terminal</a></td><td valign="top"><a href="#Input_002fOutput">3.4 Your script’s input and output</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-tracebacks">tracebacks</a></td><td valign="top"><a href="#Backtrace">4.6.2 Backtraces (‘<samp>where</samp>’)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-tracing-debugger-commands">tracing debugger commands</a></td><td valign="top"><a href="#Command_002dTracing">4.14.11 Debugger Commands Tracing (‘<samp>set trace-commands</samp>’, ‘<samp>show trace-commands</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="General-Index-1_cp_letter-V">V</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-version-number">version number</a></td><td valign="top"><a href="#Show">4.5.2 Show information about the debugger (‘<samp>show</samp>’)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="General-Index-1_cp_letter-W">W</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-watchpoints">watchpoints</a></td><td valign="top"><a href="#Breakpoints">4.4.1 Breakpoints, watchpoints (‘<samp>break</samp>’, ‘<samp>tbreak</samp>’, ‘<samp>watch</samp>’, ‘<samp>watche</samp>’...)</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-watchpoints-numbers">watchpoints numbers</a></td><td valign="top"><a href="#Breakpoints">4.4.1 Breakpoints, watchpoints (‘<samp>break</samp>’, ‘<samp>tbreak</samp>’, ‘<samp>watch</samp>’, ‘<samp>watche</samp>’...)</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
</table>
<table><tr><th valign="top">Jump to: </th><td><a href="#General-Index-1_cp_symbol-1" class="summary-letter"><b>$</b></a>
<a href="#General-Index-1_cp_symbol-2" class="summary-letter"><b>-</b></a>
<a href="#General-Index-1_cp_symbol-3" class="summary-letter"><b>.</b></a>
<br>
<a href="#General-Index-1_cp_letter-A" class="summary-letter"><b>A</b></a>
<a href="#General-Index-1_cp_letter-B" class="summary-letter"><b>B</b></a>
<a href="#General-Index-1_cp_letter-C" class="summary-letter"><b>C</b></a>
<a href="#General-Index-1_cp_letter-D" class="summary-letter"><b>D</b></a>
<a href="#General-Index-1_cp_letter-E" class="summary-letter"><b>E</b></a>
<a href="#General-Index-1_cp_letter-F" class="summary-letter"><b>F</b></a>
<a href="#General-Index-1_cp_letter-G" class="summary-letter"><b>G</b></a>
<a href="#General-Index-1_cp_letter-H" class="summary-letter"><b>H</b></a>
<a href="#General-Index-1_cp_letter-I" class="summary-letter"><b>I</b></a>
<a href="#General-Index-1_cp_letter-L" class="summary-letter"><b>L</b></a>
<a href="#General-Index-1_cp_letter-N" class="summary-letter"><b>N</b></a>
<a href="#General-Index-1_cp_letter-O" class="summary-letter"><b>O</b></a>
<a href="#General-Index-1_cp_letter-P" class="summary-letter"><b>P</b></a>
<a href="#General-Index-1_cp_letter-R" class="summary-letter"><b>R</b></a>
<a href="#General-Index-1_cp_letter-S" class="summary-letter"><b>S</b></a>
<a href="#General-Index-1_cp_letter-T" class="summary-letter"><b>T</b></a>
<a href="#General-Index-1_cp_letter-V" class="summary-letter"><b>V</b></a>
<a href="#General-Index-1_cp_letter-W" class="summary-letter"><b>W</b></a>
</td></tr></table>
<hr size="6">
<a name="SEC_Foot"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Top" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Function-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<h1>Footnotes</h1>
<h3><a name="FOOT1" href="#DOCF1">(1)</a></h3>
<p>Recall that
variables in <acronym>BASH</acronym> don’t need to be declared before they are
referred to and that the default value would be the a null value which
here prints as an empty string.
</p><h3><a name="FOOT2" href="#DOCF2">(2)</a></h3>
<p>And in the interest of full disclosure, although
this was not shown in the example it is possible to add the <code>--</code>
<em>after</em> the script name to be debugged but before the first
program option with a dash.
</p><h3><a name="FOOT3" href="#DOCF3">(3)</a></h3>
<p>The DJGPP
port of the <acronym>BASH</acronym> debugger uses the name ‘<tt>bashdb.ini</tt>’ instead, due to the
limitations of file names imposed by DOS filesystems.
</p><h3><a name="FOOT4" href="#DOCF4">(4)</a></h3>
<p>On
DOS/Windows systems, the home directory is the one pointed to by the
<code>HOME</code> environment variable.
</p><hr size="1">
<a name="SEC_Contents"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Top" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Function-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<h1>Table of Contents</h1>
<div class="contents">
<ul class="toc">
<li><a name="toc-Summary-of-the-BASH-Debugger" href="#Summary">1. Summary of the BASH Debugger</a>
<ul class="toc">
<li><a name="toc-A-Sample-BASH-Debugger-Session" href="#Sample-Session">1.1 A Sample BASH Debugger Session</a></li>
<li><a name="toc-Interactive-Line-Tracing-Session-1" href="#Interactive-Line-Tracing-Session">1.2 Interactive Line Tracing Session</a></li>
</ul></li>
<li><a name="toc-Getting-in-and-out" href="#Invocation">2. Getting in and out</a>
<ul class="toc">
<li><a name="toc-Starting-the-BASH-debugger-1" href="#Starting-the-BASH-debugger">2.1 Starting the BASH debugger</a>
<ul class="toc">
<li><a name="toc-Command_002dline-options-for-bashdb-script" href="#Options-for-the-bashdb-script">2.1.1 Command-line options for <code>bashdb</code> script</a></li>
</ul></li>
<li><a name="toc-Quitting-the-BASH-debugger-1" href="#Quitting-the-BASH-debugger">2.2 Quitting the BASH debugger</a></li>
<li><a name="toc-Calling-the-BASH-debugger-from-inside-your-program" href="#Calling-from-Program">2.3 Calling the BASH debugger from inside your program</a>
<ul class="toc">
<li><a name="toc-Debugging-a-Running-Shell-Script" href="#Debugging-a-Running-Shell-Script">2.3.1 Debugging a Running Shell Script</a>
<ul class="toc">
<li><a name="toc-Explicit-Debugging-Calls_002e" href="#Explicit-Debugging-Calls_002e">2.3.1.1 Explicit Debugging Calls.</a></li>
</ul></li>
<li><a name="toc-Program_002dControlled-Line-Tracing-1" href="#Program_002dControlled-Line-Tracing">2.3.2 Program-Controlled Line Tracing</a></li>
</ul>
</li>
</ul></li>
<li><a name="toc-Script-Setup-inside-the-BASH-Debugger" href="#Running">3. Script Setup inside the BASH Debugger</a>
<ul class="toc">
<li><a name="toc-Starting-your-script" href="#Starting">3.1 Starting your script</a></li>
<li><a name="toc-Command-files" href="#Command-Files">3.2 Command files</a></li>
<li><a name="toc-Your-script_0027s-arguments" href="#Arguments">3.3 Your script’s arguments</a></li>
<li><a name="toc-Your-script_0027s-input-and-output" href="#Input_002fOutput">3.4 Your script’s input and output</a></li>
<li><a name="toc-Script_002fDebugger-Interaction-1" href="#Script_002fDebugger-Interaction">3.5 Script/Debugger Interaction</a></li>
</ul></li>
<li><a name="toc-BASH-Debugger-Command-Reference" href="#Debugger-Command-Reference">4. BASH Debugger Command Reference</a>
<ul class="toc">
<li><a name="toc-Command-syntax" href="#Command-Syntax">4.1 Command syntax</a></li>
<li><a name="toc-Getting-help-_0028help_0029" href="#Help">4.2 Getting help (‘<samp>help</samp>’)</a></li>
<li><a name="toc-Quitting-the-BASH-debugger-_0028quit_002c-kill_0029" href="#Quit">4.3 Quitting the BASH debugger (‘<samp>quit</samp>’, ‘<samp>kill</samp>’)</a></li>
<li><a name="toc-Stopping-and-Resuming-Execution" href="#Stopping">4.4 Stopping and Resuming Execution</a>
<ul class="toc">
<li><a name="toc-Breakpoints_002c-watchpoints-_0028break_002c-tbreak_002c-watch_002c-watche_002e_002e_002e_0029" href="#Breakpoints">4.4.1 Breakpoints, watchpoints (‘<samp>break</samp>’, ‘<samp>tbreak</samp>’, ‘<samp>watch</samp>’, ‘<samp>watche</samp>’...)</a>
<ul class="toc">
<li><a name="toc-Setting-breakpoints-_0028break-tbreak_0029" href="#Set-Breaks">4.4.1.1 Setting breakpoints (‘<samp>break</samp>’ ‘<samp>tbreak</samp>’)</a></li>
<li><a name="toc-Setting-watchpoints-_0028watch_002c-watche_0029" href="#Set-Watchpoints">4.4.1.2 Setting watchpoints (‘<samp>watch</samp>’, ‘<samp>watche</samp>’)</a></li>
<li><a name="toc-Breakpoint-command-lists-_0028commands_0029" href="#Break-Commands">4.4.1.3 Breakpoint command lists (‘<samp>commands</samp>’)</a></li>
<li><a name="toc-Deleting-breakpoints-_0028clear_002c-delete_0029" href="#Delete-Breaks">4.4.1.4 Deleting breakpoints (‘<samp>clear</samp>’, ‘<samp>delete</samp>’)</a></li>
<li><a name="toc-Disabling-breakpoints-_0028disable_002c-enable_0029" href="#Disabling">4.4.1.5 Disabling breakpoints (‘<samp>disable</samp>’, ‘<samp>enable</samp>’)</a></li>
<li><a name="toc-Break-conditions-_0028condition_0029" href="#Conditions">4.4.1.6 Break conditions (‘<samp>condition</samp>’)</a></li>
</ul></li>
<li><a name="toc-Resuming-Execution-_0028step_002c-next_002c-finish_002c-skip_002c-continue_002c-debug_002c-return_0029" href="#Resuming-Execution">4.4.2 Resuming Execution (‘<samp>step</samp>’, ‘<samp>next</samp>’, ‘<samp>finish</samp>’, ‘<samp>skip</samp>’, ‘<samp>continue</samp>’, ‘<samp>debug</samp>’, ‘<samp>return</samp>’)</a>
<ul class="toc">
<li><a name="toc-Step-_0028step_0029" href="#Step">4.4.2.1 Step (‘<samp>step</samp>’)</a></li>
<li><a name="toc-Next-_0028next_0029" href="#Next">4.4.2.2 Next (‘<samp>next</samp>’)</a></li>
<li><a name="toc-Finish-_0028finish_0029" href="#Finish">4.4.2.3 Finish (‘<samp>finish</samp>’)</a></li>
<li><a name="toc-Skip-_0028skip_0029" href="#Skip">4.4.2.4 Skip (‘<samp>skip</samp>’)</a></li>
<li><a name="toc-Continue-_0028continue_0029" href="#Continue">4.4.2.5 Continue (‘<samp>continue</samp>’)</a></li>
<li><a name="toc-Debug-_0028debug_0029" href="#Debug">4.4.2.6 Debug (‘<samp>debug</samp>’)</a></li>
<li><a name="toc-Returning-from-a-function_002c-sourced-file_002c-or-subshell-_0028return_0029" href="#Returning">4.4.2.7 Returning from a function, sourced file, or subshell (‘<samp>return</samp>’)</a></li>
</ul></li>
<li><a name="toc-Signals-_0028handle_002c-info-handle_002c-signal_0029" href="#Signals">4.4.3 Signals (‘<samp>handle</samp>’, ‘<samp>info handle</samp>’, ‘<samp>signal</samp>’)</a>
<ul class="toc">
<li><a name="toc-Intercepting-Signals-_0028handle_002c-info-handle_0029" href="#handle">4.4.3.1 Intercepting Signals (‘<samp>handle</samp>’, ‘<samp>info handle</samp>’)</a></li>
<li><a name="toc-Sending-your-program-a-signal-_0028signal_0029" href="#signal">4.4.3.2 Sending your program a signal (‘<samp>signal</samp>’)</a></li>
</ul>
</li>
</ul></li>
<li><a name="toc-Status-and-Debugger-Settings-_0028info_002c-show_0029" href="#Program-Information">4.5 Status and Debugger Settings (‘<samp>info</samp>’, ‘<samp>show</samp>’)</a>
<ul class="toc">
<li><a name="toc-Showing-information-about-the-program-being-debugged-_0028info_0029" href="#Info">4.5.1 Showing information about the program being debugged (‘<samp>info</samp>’)</a></li>
<li><a name="toc-Show-information-about-the-debugger-_0028show_0029" href="#Show">4.5.2 Show information about the debugger (‘<samp>show</samp>’)</a></li>
</ul></li>
<li><a name="toc-Examining-the-Stack-Frame-_0028where_002c-frame_002c-up_002c-down_0029" href="#Stack">4.6 Examining the Stack Frame (‘<samp>where</samp>’, ‘<samp>frame</samp>’, ‘<samp>up</samp>’, ‘<samp>down</samp>’)</a>
<ul class="toc">
<li><a name="toc-Stack-frames" href="#Frames">4.6.1 Stack frames</a></li>
<li><a name="toc-Backtraces-_0028where_0029" href="#Backtrace">4.6.2 Backtraces (‘<samp>where</samp>’)</a></li>
<li><a name="toc-Selecting-a-frame-_0028up_002c-down_002c-frame_0029" href="#Selection">4.6.3 Selecting a frame (‘<samp>up</samp>’, ‘<samp>down</samp>’, ‘<samp>frame</samp>’)</a></li>
</ul></li>
<li><a name="toc-Examining-Source-Files-_0028list_0029" href="#List">4.7 Examining Source Files (‘<samp>list</samp>’)</a></li>
<li><a name="toc-Editing-Source-files-_0028edit_0029" href="#Edit">4.8 Editing Source files (‘<samp>edit</samp>’)</a></li>
<li><a name="toc-Searching-source-files-_0028search_002c-reverse_002c-_002f_002e_002e_002e_002f_002c-_003f_002e_002e_003f_0029" href="#Search">4.9 Searching source files (‘<samp>search</samp>’, ‘<samp>reverse</samp>’, ‘<samp>/.../</samp>’, ‘<samp>?..?</samp>’)</a></li>
<li><a name="toc-Examining-Data-_0028print_002c-examine_002c-info-variables_0029" href="#Data">4.10 Examining Data (‘<samp>print</samp>’, ‘<samp>examine</samp>’, ‘<samp>info variables</samp>’)</a></li>
<li><a name="toc-Running-Arbitrary-BASH-and-Shell-commands-_0028eval_002c-shell_0029" href="#Evaluation_002fExecution">4.11 Running Arbitrary BASH and Shell commands (‘<samp>eval</samp>’, ‘<samp>shell</samp>’)</a></li>
<li><a name="toc-Interfacing-to-the-OS-_0028cd_002c-pwd_0029" href="#Interfacing-to-the-OS">4.12 Interfacing to the OS (‘<samp>cd</samp>’, ‘<samp>pwd</samp>’)</a></li>
<li><a name="toc-Automatic-display-_0028display_002c-undisplay_0029" href="#Auto-Display">4.13 Automatic display (‘<samp>display</samp>’, ‘<samp>undisplay</samp>’)</a></li>
<li><a name="toc-Controlling-bashdb-_0028set_002c-file_002c-prompt_002c-history_002e_002e_002e_0029" href="#Controlling-bashdb">4.14 Controlling bashdb (‘<samp>set</samp>’, ‘<samp>file</samp>’, ‘<samp>prompt</samp>’, ‘<samp>history</samp>’...)</a>
<ul class="toc">
<li><a name="toc-Debugger-Command-Aliases-_0028alias_0029" href="#Alias">4.14.1 Debugger Command Aliases (‘<samp>alias</samp>’)</a></li>
<li><a name="toc-Annotation-Level-_0028set-annotate_0029" href="#Annotate">4.14.2 Annotation Level (‘<samp>set annotate</samp>’)</a></li>
<li><a name="toc-Set_002fShow-auto_002deval-_0028set-autoeval_0029" href="#Autoeval">4.14.3 Set/Show auto-eval (‘<samp>set autoeval</samp>’)</a></li>
<li><a name="toc-File-basename-_0028set-basename_0029" href="#Basename">4.14.4 File basename (‘<samp>set basename</samp>’)</a></li>
<li><a name="toc-Allow-Debugging-the-debugger-_0028set-debugger_0029" href="#Debugger">4.14.5 Allow Debugging the debugger (‘<samp>set debugger</samp>’)</a></li>
<li><a name="toc-Specifying-a-Script_002dFile-Association-_0028file_0029" href="#File">4.14.6 Specifying a Script-File Association (‘<samp>file</samp>’)</a></li>
<li><a name="toc-Show-position-information-as-statements-are-executed-_0028set-linetrace_0029" href="#Line-Tracing">4.14.7 Show position information as statements are executed (‘<samp>set linetrace</samp>’)</a></li>
<li><a name="toc-Logging-output-_0028set-logging_002c-set-logging-file_002e_002e_002e_0029" href="#Logging">4.14.8 Logging output (‘<samp>set logging</samp>’, ‘<samp>set logging file</samp>’...)</a></li>
<li><a name="toc-Prompt-_0028set-prompt_002c-show-prompt_0029" href="#Prompt">4.14.9 Prompt (‘<samp>set prompt</samp>’, ‘<samp>show prompt</samp>’)</a></li>
<li><a name="toc-Command-editing-_0028set-editing_002c-show-editing_0029" href="#Editing">4.14.10 Command editing (‘<samp>set editing</samp>’, ‘<samp>show editing</samp>’)</a></li>
<li><a name="toc-Debugger-Commands-Tracing-_0028set-trace_002dcommands_002c-show-trace_002dcommands_0029" href="#Command_002dTracing">4.14.11 Debugger Commands Tracing (‘<samp>set trace-commands</samp>’, ‘<samp>show trace-commands</samp>’)</a></li>
<li><a name="toc-Command-Display-_0028set-showcommand_0029" href="#Command-Display">4.14.12 Command Display (‘<samp>set showcommand</samp>’)</a></li>
<li><a name="toc-Command-history-_0028H_002c-history_002c-_0021_0029" href="#History">4.14.13 Command history (‘<samp>H</samp>’, ‘<samp>history</samp>’, ‘<samp>!</samp>’)</a></li>
<li><a name="toc-Command-Completion-_0028complete_0029" href="#Command-Completion">4.14.14 Command Completion (‘<samp>complete</samp>’)</a></li>
</ul>
</li>
</ul></li>
<li><a name="toc-Using-the-BASH-debugger-from-a-front_002dend-user-interface" href="#Front-Ends">5. Using the <acronym>BASH</acronym> debugger from a front-end user interface</a>
<ul class="toc">
<li><a name="toc-Using-the-BASH-debugger-from-GNU-Emacs" href="#Emacs">5.1 Using the <acronym>BASH</acronym> debugger from <small>GNU</small> Emacs</a>
<ul class="toc">
<li><a name="toc-Commands-from-the-GUD-buffer" href="#GUD">5.1.1 Commands from the GUD buffer</a></li>
<li><a name="toc-Commands-from-the-source-script" href="#Emacs-Source">5.1.2 Commands from the source script</a></li>
<li><a name="toc-the-BASH-debugger-from-a-GNU-Emacs-Shell" href="#Emacs-Shell">5.1.3 the <acronym>BASH</acronym> debugger from a <small>GNU</small> Emacs Shell</a></li>
</ul></li>
<li><a name="toc-Using-the-BASH-debugger-from-DDD" href="#DDD">5.2 Using the <acronym>BASH</acronym> debugger from <acronym>DDD</acronym></a></li>
</ul></li>
<li><a name="toc-Reporting-Bugs" href="#BASH-Debugger-Bugs">6. Reporting Bugs</a>
<ul class="toc">
<li><a name="toc-Have-you-found-a-bug_003f" href="#Bug-Criteria">6.1 Have you found a bug?</a></li>
<li><a name="toc-How-to-report-bugs" href="#Bug-Reporting">6.2 How to report bugs</a></li>
</ul></li>
<li><a name="toc-History-and-Acknowledgments-1" href="#History-and-Acknowledgments">7. History and Acknowledgments</a></li>
<li><a name="toc-GNU-GENERAL-PUBLIC-LICENSE" href="#Copying">A. GNU GENERAL PUBLIC LICENSE</a></li>
<li><a name="toc-GNU-Free-Documentation-License-1" href="#GNU-Free-Documentation-License">B. GNU Free Documentation License</a></li>
<li><a name="toc-Function-Index-1" href="#Function-Index">Function Index</a></li>
<li><a name="toc-Command-Index-1" href="#Command-Index">Command Index</a></li>
<li><a name="toc-Variable-Index-1" href="#Variable-Index">Variable Index</a></li>
<li><a name="toc-General-Index-1" href="#General-Index">General Index</a></li>
</ul>
</div>
<hr size="1">
<a name="SEC_About"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Top" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Function-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<h1>About This Document</h1>
<p>
This document was generated by <em>OM</em> on <em>January 9, 2010</em> using <a href="http://www.nongnu.org/texi2html/"><em>texi2html 1.82</em></a>.
</p>
<p>
The buttons in the navigation panels have the following meaning:
</p>
<table border="1">
<tr>
<th> Button </th>
<th> Name </th>
<th> Go to </th>
<th> From 1.2.3 go to</th>
</tr>
<tr>
<td align="center"> [ < ] </td>
<td align="center">Back</td>
<td>Previous section in reading order</td>
<td>1.2.2</td>
</tr>
<tr>
<td align="center"> [ > ] </td>
<td align="center">Forward</td>
<td>Next section in reading order</td>
<td>1.2.4</td>
</tr>
<tr>
<td align="center"> [ << ] </td>
<td align="center">FastBack</td>
<td>Beginning of this chapter or previous chapter</td>
<td>1</td>
</tr>
<tr>
<td align="center"> [ Up ] </td>
<td align="center">Up</td>
<td>Up section</td>
<td>1.2</td>
</tr>
<tr>
<td align="center"> [ >> ] </td>
<td align="center">FastForward</td>
<td>Next chapter</td>
<td>2</td>
</tr>
<tr>
<td align="center"> [Top] </td>
<td align="center">Top</td>
<td>Cover (top) of document</td>
<td> </td>
</tr>
<tr>
<td align="center"> [Contents] </td>
<td align="center">Contents</td>
<td>Table of contents</td>
<td> </td>
</tr>
<tr>
<td align="center"> [Index] </td>
<td align="center">Index</td>
<td>Index</td>
<td> </td>
</tr>
<tr>
<td align="center"> [ ? ] </td>
<td align="center">About</td>
<td>About (help)</td>
<td> </td>
</tr>
</table>
<p>
where the <strong> Example </strong> assumes that the current position is at <strong> Subsubsection One-Two-Three </strong> of a document of the following structure:
</p>
<ul>
<li> 1. Section One
<ul>
<li>1.1 Subsection One-One
<ul>
<li>...</li>
</ul>
</li>
<li>1.2 Subsection One-Two
<ul>
<li>1.2.1 Subsubsection One-Two-One</li>
<li>1.2.2 Subsubsection One-Two-Two</li>
<li>1.2.3 Subsubsection One-Two-Three
<strong><== Current Position </strong></li>
<li>1.2.4 Subsubsection One-Two-Four</li>
</ul>
</li>
<li>1.3 Subsection One-Three
<ul>
<li>...</li>
</ul>
</li>
<li>1.4 Subsection One-Four</li>
</ul>
</li>
</ul>
<hr size="1">
<p>
<font size="-1">
This document was generated by <em>OM</em> on <em>January 9, 2010</em> using <a href="http://www.nongnu.org/texi2html/"><em>texi2html 1.82</em></a>.
</font>
<br>
</p>
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