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<a name="Debug-Mode"></a>
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<p>
Next: <a href="Call-Stack.html#Call-Stack" accesskey="n" rel="next">Call Stack</a>, Previous: <a href="Breakpoints.html#Breakpoints" accesskey="p" rel="prev">Breakpoints</a>, Up: <a href="Debugging.html#Debugging" accesskey="u" rel="up">Debugging</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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<hr>
<a name="Debug-Mode-1"></a>
<h3 class="section">13.4 Debug Mode</h3>
<p>There are three additional support functions that allow the user to
find out where in the execution of a script Octave entered the debug
mode, and to print the code in the script surrounding the point where
Octave entered debug mode.
</p>
<a name="XREFdbwhere"></a><dl>
<dt><a name="index-dbwhere"></a>Command: <em></em> <strong>dbwhere</strong></dt>
<dd><p>In debugging mode, report the current file and line number where
execution is stopped.
</p>
<p><strong>See also:</strong> <a href="Breakpoints.html#XREFdbstatus">dbstatus</a>, <a href="Leaving-Debug-Mode.html#XREFdbcont">dbcont</a>, <a href="#XREFdbstep">dbstep</a>, <a href="Call-Stack.html#XREFdbup">dbup</a>.
</p></dd></dl>
<a name="XREFdbtype"></a><dl>
<dt><a name="index-dbtype"></a>Command: <em></em> <strong>dbtype</strong></dt>
<dt><a name="index-dbtype-1"></a>Command: <em></em> <strong>dbtype</strong> <em><var>lineno</var></em></dt>
<dt><a name="index-dbtype-2"></a>Command: <em></em> <strong>dbtype</strong> <em><var>startl:endl</var></em></dt>
<dt><a name="index-dbtype-3"></a>Command: <em></em> <strong>dbtype</strong> <em><var>startl:end</var></em></dt>
<dt><a name="index-dbtype-4"></a>Command: <em></em> <strong>dbtype</strong> <em><var>func</var></em></dt>
<dt><a name="index-dbtype-5"></a>Command: <em></em> <strong>dbtype</strong> <em><var>func</var> <var>lineno</var></em></dt>
<dt><a name="index-dbtype-6"></a>Command: <em></em> <strong>dbtype</strong> <em><var>func</var> <var>startl:endl</var></em></dt>
<dt><a name="index-dbtype-7"></a>Command: <em></em> <strong>dbtype</strong> <em><var>func</var> <var>startl:end</var></em></dt>
<dd><p>Display a script file with line numbers.
</p>
<p>When called with no arguments in debugging mode, display the script file
currently being debugged. An optional range specification can be used to
list only a portion of the file. The special keyword <code>"end"</code> is a
valid line number specification for the last line of the file.
</p>
<p>When called with the name of a function, list that script file with line
numbers.
</p>
<p><strong>See also:</strong> <a href="#XREFdbwhere">dbwhere</a>, <a href="Breakpoints.html#XREFdbstatus">dbstatus</a>, <a href="Breakpoints.html#XREFdbstop">dbstop</a>.
</p></dd></dl>
<a name="XREFdblist"></a><dl>
<dt><a name="index-dblist"></a>Command: <em></em> <strong>dblist</strong></dt>
<dt><a name="index-dblist-1"></a>Command: <em></em> <strong>dblist</strong> <em><var>n</var></em></dt>
<dd><p>In debugging mode, list <var>n</var> lines of the function being debugged
centered around the current line to be executed. If unspecified <var>n</var>
defaults to 10 (+/- 5 lines)
</p>
<p><strong>See also:</strong> <a href="#XREFdbwhere">dbwhere</a>, <a href="#XREFdbtype">dbtype</a>.
</p></dd></dl>
<p>You may also use <code>isdebugmode</code> to determine whether the debugger is
currently active.
</p>
<a name="XREFisdebugmode"></a><dl>
<dt><a name="index-isdebugmode"></a>Built-in Function: <em></em> <strong>isdebugmode</strong> <em>()</em></dt>
<dd><p>Return true if in debugging mode, otherwise false.
</p>
<p><strong>See also:</strong> <a href="#XREFdbwhere">dbwhere</a>, <a href="Call-Stack.html#XREFdbstack">dbstack</a>, <a href="Breakpoints.html#XREFdbstatus">dbstatus</a>.
</p></dd></dl>
<p>Debug mode also allows single line stepping through a function using
the command <code>dbstep</code>.
</p>
<a name="XREFdbstep"></a><dl>
<dt><a name="index-dbstep"></a>Command: <em></em> <strong>dbstep</strong></dt>
<dt><a name="index-dbstep-1"></a>Command: <em></em> <strong>dbstep</strong> <em><var>n</var></em></dt>
<dt><a name="index-dbstep-2"></a>Command: <em></em> <strong>dbstep</strong> <em>in</em></dt>
<dt><a name="index-dbstep-3"></a>Command: <em></em> <strong>dbstep</strong> <em>out</em></dt>
<dt><a name="index-dbnext"></a>Command: <em></em> <strong>dbnext</strong> <em>…</em></dt>
<dd><p>In debugging mode, execute the next <var>n</var> lines of code.
If <var>n</var> is omitted, execute the next single line of code.
If the next line of code is itself defined in terms of an m-file remain in
the existing function.
</p>
<p>Using <code>dbstep in</code> will cause execution of the next line to step into
any m-files defined on the next line. Using <code>dbstep out</code> will cause
execution to continue until the current function returns.
</p>
<p><code>dbnext</code> is an alias for <code>dbstep</code>.
</p>
<p><strong>See also:</strong> <a href="Leaving-Debug-Mode.html#XREFdbcont">dbcont</a>, <a href="Leaving-Debug-Mode.html#XREFdbquit">dbquit</a>.
</p></dd></dl>
<p>When in debug mode the <tt class="key">RETURN</tt> key will execute the last entered command.
This is useful, for example, after hitting a breakpoint and entering
<code>dbstep</code> once. After that, one can advance line by line through the code
with only a single key stroke.
</p>
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