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<html><title>Programming Ruby: The Pragmatic Programmer's Guide</title><head><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><STYLE TYPE="text/css"><!--
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   </STYLE><table bgcolor="#a03030" cellpadding="3" border="0" cellspacing="0"><tr><td colspan="3"><table bgcolor="#902020" cellpadding="20"><tr><td><h1 class="header">Programming Ruby</h1><h3 class="subheader">The Pragmatic Programmer's Guide</h3></td></tr></table></td></tr><tr><td width="33%" align="left"><a class="subheader" href="ref_c_symbol.html">Previous &lt;</a></td><td width="33%" align="center" valign="middle"><a class="subheader" href="builtins.html">Contents ^</a><br></td><td width="33%" align="right"><a class="subheader" href="ref_c_threadgroup.html">Next ></a><br></td></tr></table></head><body bgcolor="white">
<!--
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<table><tr><td height="20"><img src="dot.gif" width="1" height="20"></td></tr></table><table border="0" width="100%" bgcolor="660066" cellpadding="10"><tr><td valign="center"><font color="white" size="7">class Thread</font></td><td><table border="0"><tr><td><font color="white">
                Parent:
              </font></td><td><font color="white">Object</font></td></tr><tr><td><font color="white">
                Version:
              </font></td><td><font color="white">
               1.6
              </font></td></tr></table></td></tr></table><p></p><H3>Index:</H3><a href="#abort_on_exception">abort_on_exception</a> <a href="#abort_on_exception_eq">abort_on_exception=</a> <a href="#critical">critical</a> <a href="#critical_eq">critical=</a> <a href="#current">current</a> <a href="#exit">exit</a> <a href="#fork">fork</a> <a href="#kill">kill</a> <a href="#list">list</a> <a href="#main">main</a> <a href="#new">new</a> <a href="#pass">pass</a> <a href="#start">start</a> <a href="#stop">stop</a> <a href="#_ob_cb"><i>[ ]</i></a> <a href="#_ob_cb_eq"><i>[ ]=</i></a> <a href="#abort_on_exception"><i>abort_on_exception</i></a> <a href="#abort_on_exception_eq"><i>abort_on_exception=</i></a> <a href="#alive_qm"><i>alive?</i></a> <a href="#exit"><i>exit</i></a> <a href="#join"><i>join</i></a> <a href="#key_qm"><i>key?</i></a> <a href="#kill"><i>kill</i></a> <a href="#priority"><i>priority</i></a> <a href="#priority_eq"><i>priority=</i></a> <a href="#raise"><i>raise</i></a> <a href="#run"><i>run</i></a> <a href="#safe_level"><i>safe_level</i></a> <a href="#status"><i>status</i></a> <a href="#stop_qm"><i>stop?</i></a> <a href="#value"><i>value</i></a> <a href="#wakeup"><i>wakeup</i></a> <p></p><hr>
<P></P>
  <code>Thread</code> encapsulates the behavior of a thread of execution,
  including the main thread of the Ruby script. See the tutorial in
  Chapter 11, beginning on page 113.
<P></P>
  In the descriptions that follow, the
  parameter <i>aSymbol</i> refers to a symbol, which is either a
  quoted string or a <code>Symbol</code> (such as <code>:name</code>).<table border="0" width="100%" cellpadding="10"><tr><td valign="center" colspan="2" bgcolor="990066"><font color="white" size="6">class methods
       </font></td></tr><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="abort_on_exception"><b>abort_on_exception</b></a></font></td><td bgcolor="#ffaaaa">
        Thread.abort_on_exception
        -> <code>true</code> or <code>false</code>
      </td></tr><td></td><td>
              Returns the status of the global ``abort on exception''
      condition.  The default is <code>false</code>.      
      When set to <code>true</code>, will cause all threads to abort (the
      process will <code>exit(0)</code>) if an
      exception is raised in any thread. See also <a href="ref_c_thread.html#abort_on_exception_eq"><code>Thread::abort_on_exception=</code></a>.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="abort_on_exception_eq"><b>abort_on_exception=</b></a></font></td><td bgcolor="#ffaaaa">
        Thread.abort_on_exception= 
        <i>aBoolean</i>-> <code>true</code> or <code>false</code>
      </td></tr><td></td><td>
<P></P>
      When set to <code>true</code>, all threads will abort if an
      exception is raised. Returns the new state.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
Thread.abort_on_exception&nbsp;=&nbsp;true
t1&nbsp;=&nbsp;Thread.new&nbsp;do
&nbsp;&nbsp;puts&nbsp;&nbsp;"In&nbsp;second&nbsp;thread"
&nbsp;&nbsp;raise&nbsp;"Raise&nbsp;exception"
end
t1.join
print&nbsp;"not&nbsp;reached\n"
</pre></td></tr></table>

<em>produces:</em>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
In&nbsp;second&nbsp;thread
prog.rb:4:&nbsp;Raise&nbsp;exception&nbsp;(RuntimeError)
	from&nbsp;prog.rb:2:in&nbsp;`initialize'
	from&nbsp;prog.rb:2:in&nbsp;`new'
	from&nbsp;prog.rb:2
</pre></td></tr></table>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="critical"><b>critical</b></a></font></td><td bgcolor="#ffaaaa">
        Thread.critical
        -> <code>true</code> or <code>false</code>
      </td></tr><td></td><td>
<P></P>
      Returns the status of the global ``thread critical''
      condition. 
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="critical_eq"><b>critical=</b></a></font></td><td bgcolor="#ffaaaa">
        Thread.critical= <i>aBoolean</i>
        -> <code>true</code> or <code>false</code>
      </td></tr><td></td><td>
<P></P>
      Sets the status of the global ``thread critical''
      condition and returns it.
      When set to <code>true</code>, prohibits scheduling of any existing
      thread.  Does not block new threads from being created and run.
      Certain thread operations (such as stopping or killing a thread,
      sleeping in the current thread, and raising an exception) may
      cause a thread to be scheduled even when in a critical section.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
count=0
Thread.new&nbsp;{&nbsp;while&nbsp;true;&nbsp;sleep(1);&nbsp;print&nbsp;"a&nbsp;";&nbsp;count+=1;&nbsp;end&nbsp;}
while&nbsp;count&nbsp;&lt;&nbsp;3&nbsp;do&nbsp;end&nbsp;#&nbsp;no-op&nbsp;wait
Thread.critical&nbsp;=&nbsp;true
puts&nbsp;"no&nbsp;more&nbsp;a's&nbsp;will&nbsp;come&nbsp;out."
</pre></td></tr></table>

<em>produces:</em>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
a&nbsp;a&nbsp;a&nbsp;no&nbsp;more&nbsp;a's&nbsp;will&nbsp;come&nbsp;out.
</pre></td></tr></table>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="current"><b>current</b></a></font></td><td bgcolor="#ffaaaa">
        Thread.current
        -> <i>aThread</i>
      </td></tr><td></td><td>
<P></P>
      Returns the currently executing thread.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
  <td valign="top"><code>Thread.current</code></td>
  <td valign="top"></td>
  <td valign="top"><code>#&lt;Thread:0x40196528&nbsp;run></code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="exit"><b>exit</b></a></font></td><td bgcolor="#ffaaaa">
        Thread.exit
      </td></tr><td></td><td>
<P></P>
      Terminates the currently running thread and schedules another
      thread to be run.  If this thread is already marked to be
      killed, <code>exit</code> returns the <code>Thread</code>.  If this is the main thread, or
      the last thread, exit the process.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="fork"><b>fork</b></a></font></td><td bgcolor="#ffaaaa">
        Thread.fork { block }
-> <i>aThread</i>
      </td></tr><td></td><td>
<P></P>
      Synonym for <a href="ref_c_thread.html#new"><code>Thread::new</code></a>.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="kill"><b>kill</b></a></font></td><td bgcolor="#ffaaaa">
        Thread.kill( <i>aThread</i> )
      </td></tr><td></td><td>
<P></P>
      Causes the given thread to exit (see <a href="ref_c_thread.html#exit"><code>Thread::exit</code></a>).
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>count&nbsp;=&nbsp;0</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>a&nbsp;=&nbsp;Thread.new&nbsp;{&nbsp;while&nbsp;true&nbsp;do&nbsp;&nbsp;count&nbsp;+=&nbsp;1&nbsp;end&nbsp;}</code></td>
</tr>
<tr>
  <td valign="top"><code>sleep(1)</code></td>
  <td valign="top"></td>
  <td valign="top"><code>1</code></td>
</tr>
<tr>
  <td valign="top"><code>Thread.kill(a)</code></td>
  <td valign="top"></td>
  <td valign="top"><code>#&lt;Thread:0x4018d52c&nbsp;dead></code></td>
</tr>
<tr>
  <td valign="top"><code>count</code></td>
  <td valign="top"></td>
  <td valign="top"><code>911276</code></td>
</tr>
<tr>
  <td valign="top"><code>a.alive?</code></td>
  <td valign="top"></td>
  <td valign="top"><code>false</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="list"><b>list</b></a></font></td><td bgcolor="#ffaaaa">
        Thread.list -> <i>anArray</i>
      </td></tr><td></td><td>
<P></P>
      Returns an array of <code>Thread</code> objects for all threads that are
      either runnable or stopped.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>Thread.new&nbsp;{&nbsp;sleep(200)&nbsp;}</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>Thread.new&nbsp;{&nbsp;1000000.times&nbsp;{|i|&nbsp;i*i&nbsp;}&nbsp;}</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>Thread.new&nbsp;{&nbsp;Thread.stop&nbsp;}</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>l&nbsp;=&nbsp;Thread.list</code></td>
</tr>
<tr>
  <td valign="top"><code>l</code></td>
  <td valign="top"></td>
  <td valign="top"><code>[#&lt;Thread:0x4018d658&nbsp;sleep>,&nbsp;#&lt;Thread:0x4018d6d0&nbsp;run>,&nbsp;#&lt;Thread:0x4018d70c&nbsp;sleep>,&nbsp;#&lt;Thread:0x40196528&nbsp;run>]</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="main"><b>main</b></a></font></td><td bgcolor="#ffaaaa">
        Thread.main
        -> <i>aThread</i>
      </td></tr><td></td><td>
<P></P>
      Returns the main thread for the process.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
  <td valign="top"><code>Thread.main</code></td>
  <td valign="top"></td>
  <td valign="top"><code>#&lt;Thread:0x40196528&nbsp;run></code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="new"><b>new</b></a></font></td><td bgcolor="#ffaaaa">
        Thread.new( <i>[</i><i>arg</i><i>]<sup>*</sup></i> ) {| args | block }
<P></P>
        -> <i>aThread</i>
      </td></tr><td></td><td>
<P></P>
      Creates a new thread to execute the instructions given in
      <i>block</i>, and begins running it. Any arguments passed to
      <a href="ref_c_thread.html#new"><code>Thread::new</code></a> are passed into the block.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
x&nbsp;=&nbsp;Thread.new&nbsp;{&nbsp;sleep&nbsp;.1;&nbsp;print&nbsp;"x";&nbsp;print&nbsp;"y";&nbsp;print&nbsp;"z"&nbsp;}
a&nbsp;=&nbsp;Thread.new&nbsp;{&nbsp;print&nbsp;"a";&nbsp;print&nbsp;"b";&nbsp;sleep&nbsp;.2;&nbsp;print&nbsp;"c"&nbsp;}
x.join&nbsp;#&nbsp;Let&nbsp;the&nbsp;threads&nbsp;finish&nbsp;before
a.join&nbsp;#&nbsp;main&nbsp;thread&nbsp;exits...
</pre></td></tr></table>

<em>produces:</em>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
abxyzc
</pre></td></tr></table>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="pass"><b>pass</b></a></font></td><td bgcolor="#ffaaaa">
        Thread.pass
      </td></tr><td></td><td>
<P></P>
      Invokes the thread scheduler to pass execution to another
      thread.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
a&nbsp;=&nbsp;Thread.new&nbsp;{&nbsp;print&nbsp;"a";&nbsp;Thread.pass;
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;print&nbsp;"b";&nbsp;Thread.pass;
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;print&nbsp;"c"&nbsp;}
b&nbsp;=&nbsp;Thread.new&nbsp;{&nbsp;print&nbsp;"x";&nbsp;Thread.pass;
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;print&nbsp;"y";&nbsp;Thread.pass;
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;print&nbsp;"z"&nbsp;}
a.join
b.join
</pre></td></tr></table>

<em>produces:</em>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
axbycz
</pre></td></tr></table>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="start"><b>start</b></a></font></td><td bgcolor="#ffaaaa">
        Thread.start( <i>[</i><i>args</i><i>]<sup>*</sup></i> ) {| args | block }
<P></P>
        -> <i>aThread</i>
      </td></tr><td></td><td>
<P></P>
      Basically the same as <a href="ref_c_thread.html#new"><code>Thread::new</code></a>. However, if class
      <code>Thread</code> is subclassed, then calling <code>start</code> in that
      subclass will not invoke the subclass's <code>initialize</code> method.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="stop"><b>stop</b></a></font></td><td bgcolor="#ffaaaa">
        Thread.stop
      </td></tr><td></td><td>
<P></P>
      Stops execution of the current thread, putting it into a
      ``sleep'' state, and schedules execution of another thread.
      Resets the ``critical'' condition to <code>false</code>.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
a&nbsp;=&nbsp;Thread.new&nbsp;{&nbsp;print&nbsp;"a";&nbsp;Thread.stop;&nbsp;print&nbsp;"c"&nbsp;}
Thread.pass
print&nbsp;"b"
a.run
a.join
</pre></td></tr></table>

<em>produces:</em>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
abc
</pre></td></tr></table>

<P></P>
      </td></table>
<P></P>
  <table border="0" width="100%" cellpadding="10"><tr><td valign="center" colspan="2" bgcolor="990066"><font color="white" size="6">instance methods
       </font></td></tr><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="_ob_cb"><b>[ ]</b></a></font></td><td bgcolor="#ffaaaa">
<P></P>
        <i>thr</i>[ <i>aSymbol</i> ] -> <i>anObject</i> or <code>nil</code>
      </td></tr><td></td><td>
<P></P>
      Attribute Reference---Returns the value of a thread-local
      variable, using either a symbol or a string name.  If the
      specified variable does not exist, returns <code>nil</code>.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
a&nbsp;=&nbsp;Thread.new&nbsp;{&nbsp;Thread.current["name"]&nbsp;=&nbsp;"A";&nbsp;Thread.stop&nbsp;}
b&nbsp;=&nbsp;Thread.new&nbsp;{&nbsp;Thread.current[:name]&nbsp;&nbsp;=&nbsp;"B";&nbsp;Thread.stop&nbsp;}
c&nbsp;=&nbsp;Thread.new&nbsp;{&nbsp;Thread.current["name"]&nbsp;=&nbsp;"C";&nbsp;Thread.stop&nbsp;}
Thread.list.each&nbsp;{|x|&nbsp;print&nbsp;x.inspect,&nbsp;x[:name],&nbsp;"\n"&nbsp;}
</pre></td></tr></table>

<em>produces:</em>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
#&lt;Thread:0x4018d3ec&nbsp;sleep>C
#&lt;Thread:0x4018d43c&nbsp;sleep>B
#&lt;Thread:0x4018d4a0&nbsp;sleep>A
#&lt;Thread:0x40196528&nbsp;run>nil
</pre></td></tr></table>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="_ob_cb_eq"><b>[ ]=</b></a></font></td><td bgcolor="#ffaaaa">
<P></P>
        <i>thr</i>[ <i>aSymbol</i> ]  = <i>anObject</i>-> <i>anObject</i>
<P></P>
      </td></tr><td></td><td>
              Attribute Assignment---Sets or creates the value of a thread-local
      variable, using either a symbol or a string. See also
      <a href="ref_c_thread.html#_ob_cb"><code>Thread#[]</code></a>.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="abort_on_exception"><b>abort_on_exception</b></a></font></td><td bgcolor="#ffaaaa">
        <i>thr</i>.abort_on_exception
        -> <code>true</code> or <code>false</code>
      </td></tr><td></td><td>
              Returns the status of the ``abort on exception''
      condition for <i>thr</i>.  The default is <code>false</code>.
      See also <a href="ref_c_thread.html#abort_on_exception_eq"><code>Thread::abort_on_exception=</code></a>.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="abort_on_exception_eq"><b>abort_on_exception=</b></a></font></td><td bgcolor="#ffaaaa">
        <i>thr</i>.abort_on_exception= 
        <code>true</code> or <code>false</code>-> <code>true</code> or <code>false</code>
      </td></tr><td></td><td>
<P></P>
            When set to <code>true</code>, causes all threads (including the main
      program) to abort if an exception is raised in <i>thr</i>.
      The process will effectively <code>exit(0)</code>.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="alive_qm"><b>alive?</b></a></font></td><td bgcolor="#ffaaaa">
        <i>thr</i>.alive?
        -> <code>true</code> or <code>false</code>
      </td></tr><td></td><td>
<P></P>
      Returns <code>true</code> if <i>thr</i> is running or sleeping.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
  <td valign="top"><code>Thread.current.alive?</code></td>
  <td valign="top"></td>
  <td valign="top"><code>true</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="exit"><b>exit</b></a></font></td><td bgcolor="#ffaaaa">
        <i>thr</i>.exit -> <i>thr</i> or <code>nil</code>
      </td></tr><td></td><td>
<P></P>
      Terminates <i>thr</i> and schedules another
      thread to be run.  If this thread is already marked to be
      killed, <code>exit</code> returns the <code>Thread</code>.  If this is the main thread, or
      the last thread, exits the process.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="join"><b>join</b></a></font></td><td bgcolor="#ffaaaa">
        <i>thr</i>.join
        -> <i>thr</i>
      </td></tr><td></td><td>
<P></P>
      The calling thread will suspend execution and run <i>thr</i>. Does
      not return until
      <i>thr</i> exits.  Any threads not joined will be killed when the
      main program exits.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
a&nbsp;=&nbsp;Thread.new&nbsp;{&nbsp;print&nbsp;"a";&nbsp;sleep(10);&nbsp;print&nbsp;"b";&nbsp;print&nbsp;"c"&nbsp;}
x&nbsp;=&nbsp;Thread.new&nbsp;{&nbsp;print&nbsp;"x";&nbsp;Thread.pass;&nbsp;print&nbsp;"y";&nbsp;print&nbsp;"z"&nbsp;}
x.join&nbsp;#&nbsp;Let&nbsp;x&nbsp;thread&nbsp;finish,&nbsp;a&nbsp;will&nbsp;be&nbsp;killed&nbsp;on&nbsp;exit.
</pre></td></tr></table>

<em>produces:</em>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
axyz
</pre></td></tr></table>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="key_qm"><b>key?</b></a></font></td><td bgcolor="#ffaaaa">
                <i>thr</i>.key?( <i>aSymbol</i> ) -> <code>true</code> or <code>false</code><br>
      </td></tr><td></td><td>
<P></P>
      Returns <code>true</code> if the given string (or symbol) exists as a 
      thread-local variable.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>me&nbsp;=&nbsp;Thread.current</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>me[:oliver]&nbsp;=&nbsp;"a"</code></td>
</tr>
<tr>
  <td valign="top"><code>me.key?(:oliver)</code></td>
  <td valign="top"></td>
  <td valign="top"><code>true</code></td>
</tr>
<tr>
  <td valign="top"><code>me.key?(:stanley)</code></td>
  <td valign="top"></td>
  <td valign="top"><code>false</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="kill"><b>kill</b></a></font></td><td bgcolor="#ffaaaa">
        <i>thr</i>.kill
      </td></tr><td></td><td>
<P></P>
      Synonym for <a href="ref_c_thread.html#exit"><code>Thread#exit</code></a>.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="priority"><b>priority</b></a></font></td><td bgcolor="#ffaaaa">
        <i>thr</i>.priority
        -> <i>anInteger</i>
      </td></tr><td></td><td>
<P></P>
            Returns the priority of <i>thr</i>.  Default is zero; 
      higher-priority threads will run before lower-priority threads.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
  <td valign="top"><code>Thread.current.priority</code></td>
  <td valign="top"></td>
  <td valign="top"><code>0</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="priority_eq"><b>priority=</b></a></font></td><td bgcolor="#ffaaaa">
        <i>thr</i>.priority= <i>anInteger</i>
        -> <i>thr</i>
      </td></tr><td></td><td>
<P></P>
            Sets the priority of <i>thr</i> to <i>anInteger</i>.
      Higher-priority threads will run before lower-priority threads.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
count1&nbsp;=&nbsp;count2&nbsp;=&nbsp;0
a&nbsp;=&nbsp;Thread.new&nbsp;do
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;loop&nbsp;{&nbsp;count1&nbsp;+=&nbsp;1&nbsp;}
&nbsp;&nbsp;&nbsp;&nbsp;end
a.priority&nbsp;=&nbsp;-1
</pre></td></tr></table>

<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>b&nbsp;=&nbsp;Thread.new&nbsp;do</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;loop&nbsp;{&nbsp;count2&nbsp;+=&nbsp;1&nbsp;}</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>&nbsp;&nbsp;&nbsp;&nbsp;end</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>b.priority&nbsp;=&nbsp;-2</code></td>
</tr>
<tr>
  <td valign="top"><code>sleep&nbsp;1</code></td>
  <td valign="top"></td>
  <td valign="top"><code>1</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>Thread.critical&nbsp;=&nbsp;1</code></td>
</tr>
<tr>
  <td valign="top"><code>count1</code></td>
  <td valign="top"></td>
  <td valign="top"><code>619920</code></td>
</tr>
<tr>
  <td valign="top"><code>count2</code></td>
  <td valign="top"></td>
  <td valign="top"><code>11586</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="raise"><b>raise</b></a></font></td><td bgcolor="#ffaaaa">
        <i>thr</i>.raise( <i>anException</i> )
      </td></tr><td></td><td>
<P></P>
      Raises an exception (see <a href="ref_m_kernel.html#raise"><code>Kernel::raise</code></a>
      on page 425 for details) from <i>thr</i>.
      The caller does not have to be <i>thr</i>.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
Thread.abort_on_exception&nbsp;=&nbsp;true
a&nbsp;=&nbsp;Thread.new&nbsp;{&nbsp;sleep(200)&nbsp;}
a.raise("Gotcha")
</pre></td></tr></table>

<em>produces:</em>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
prog.rb:3:&nbsp;Gotcha&nbsp;(RuntimeError)
	from&nbsp;prog.rb:2:in&nbsp;`initialize'
	from&nbsp;prog.rb:2:in&nbsp;`new'
	from&nbsp;prog.rb:2
</pre></td></tr></table>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="run"><b>run</b></a></font></td><td bgcolor="#ffaaaa">
        <i>thr</i>.run -> <i>thr</i>
      </td></tr><td></td><td>
<P></P>
      Wakes up <i>thr</i>, making it eligible for scheduling. If not
      in a critical section, then invokes the scheduler.  
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
a&nbsp;=&nbsp;Thread.new&nbsp;{&nbsp;puts&nbsp;"a";&nbsp;Thread.stop;&nbsp;puts&nbsp;"c"&nbsp;}
Thread.pass
puts&nbsp;"Got&nbsp;here"
a.run
a.join
</pre></td></tr></table>

<em>produces:</em>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
a
Got&nbsp;here
c
</pre></td></tr></table>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="safe_level"><b>safe_level</b></a></font></td><td bgcolor="#ffaaaa">
        <i>thr</i>.safe_level
        -> <i>anInteger</i>
      </td></tr><td></td><td>
<P></P>
      Returns the safe level in effect for <i>thr</i>.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
  <td valign="top"><code>Thread.current.safe_level</code></td>
  <td valign="top"></td>
  <td valign="top"><code>0</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="status"><b>status</b></a></font></td><td bgcolor="#ffaaaa">
        <i>thr</i>.status
        -> <i>aString</i>, <code>false</code> or <code>nil</code>
      </td></tr><td></td><td>
<P></P>
      Returns the status of <i>thr</i>: ``<code>sleep</code>'' if <i>thr</i> is sleeping 
      or waiting on I/O, ``<code>run</code>'' if <i>thr</i> is executing,
      <code>false</code> if <i>thr</i> terminated normally, and <code>nil</code> if
      <i>thr</i> terminated with an exception.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>a&nbsp;=&nbsp;Thread.new&nbsp;{&nbsp;raise("die&nbsp;now")&nbsp;}</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>b&nbsp;=&nbsp;Thread.new&nbsp;{&nbsp;Thread.stop&nbsp;}</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>c&nbsp;=&nbsp;Thread.new&nbsp;{&nbsp;Thread.exit&nbsp;}</code></td>
</tr>
<tr>
  <td valign="top"><code>a.status</code></td>
  <td valign="top"></td>
  <td valign="top"><code>nil</code></td>
</tr>
<tr>
  <td valign="top"><code>b.status</code></td>
  <td valign="top"></td>
  <td valign="top"><code>"sleep"</code></td>
</tr>
<tr>
  <td valign="top"><code>c.status</code></td>
  <td valign="top"></td>
  <td valign="top"><code>false</code></td>
</tr>
<tr>
  <td valign="top"><code>Thread.current.status</code></td>
  <td valign="top"></td>
  <td valign="top"><code>"run"</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="stop_qm"><b>stop?</b></a></font></td><td bgcolor="#ffaaaa">
        <i>thr</i>.stop?
        -> <code>true</code> or <code>false</code>
      </td></tr><td></td><td>
<P></P>
      Returns <code>true</code> if <i>thr</i> is dead or sleeping.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>a&nbsp;=&nbsp;Thread.new&nbsp;{&nbsp;Thread.stop&nbsp;}</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>b&nbsp;=&nbsp;Thread.current</code></td>
</tr>
<tr>
  <td valign="top"><code>a.stop?</code></td>
  <td valign="top"></td>
  <td valign="top"><code>true</code></td>
</tr>
<tr>
  <td valign="top"><code>b.stop?</code></td>
  <td valign="top"></td>
  <td valign="top"><code>false</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="value"><b>value</b></a></font></td><td bgcolor="#ffaaaa">
        <i>thr</i>.value
        -> <i>anObject</i>
      </td></tr><td></td><td>
<P></P>
      Waits for <i>thr</i> to complete (via <a href="ref_c_thread.html#join"><code>Thread#join</code></a>) and
      returns its value.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>a&nbsp;=&nbsp;Thread.new&nbsp;{&nbsp;2+2&nbsp;}</code></td>
</tr>
<tr>
  <td valign="top"><code>a.value</code></td>
  <td valign="top"></td>
  <td valign="top"><code>4</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="wakeup"><b>wakeup</b></a></font></td><td bgcolor="#ffaaaa">
        <i>thr</i>.wakeup
        -> <i>thr</i>
      </td></tr><td></td><td>
<P></P>
      Marks <i>thr</i> as eligible for scheduling (it may still remain
      blocked on I/O, however). Does not invoke the scheduler (see
      <a href="ref_c_thread.html#run"><code>Thread#run</code></a>).
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
c&nbsp;=&nbsp;Thread.new&nbsp;{&nbsp;Thread.stop;&nbsp;puts&nbsp;"hey!"&nbsp;}
c.wakeup
</pre></td></tr></table>

<em>produces:</em>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
hey!
</pre></td></tr></table>

<P></P>
      </td></table>
<P></P>

<p></p><hr><table bgcolor="#a03030" cellpadding="10" border="0" cellspacing="0"><tr><td width="33%" align="left"><a class="subheader" href="ref_c_symbol.html">Previous &lt;</a></td><td width="33%" align="center" valign="middle"><a class="subheader" href="builtins.html">Contents ^</a><br></td><td width="33%" align="right"><a class="subheader" href="ref_c_threadgroup.html">Next ></a><br></td></tr></table><p></p><font size="-1">Extracted from the book "Programming Ruby -
     The Pragmatic Programmer's Guide"</font><br><font size="-3">
      Copyright
      &#169;
      2000 Addison Wesley Longman, Inc. Released under the terms of the
      <a href="http://www.opencontent.org/openpub/">Open Publication License</a> V1.0.
        <br>
      This reference is available for
        <a href="http://www.pragmaticprogrammer.com/ruby/downloads/book.html">download</a>.
   </font></body></html>