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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_m_objectspace.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"></td></tr></table></head><body bgcolor="white">
<!--
    Copyright (c) 2001 by Addison Wesley Longman.  This
    material may be distributed only subject to the terms and
    conditions set forth in the Open Publication License, v1.0 or
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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">module Process</font></td></tr></table><p></p><H3>Index:</H3><a href="#egid">egid</a> <a href="#egid_eq">egid=</a> <a href="#euid">euid</a> <a href="#euid_eq">euid=</a> <a href="#exit_oh">exit!</a> <a href="#fork">fork</a> <a href="#getpgid">getpgid</a> <a href="#getpgrp">getpgrp</a> <a href="#getpriority">getpriority</a> <a href="#gid">gid</a> <a href="#gid_eq">gid=</a> <a href="#kill">kill</a> <a href="#pid">pid</a> <a href="#ppid">ppid</a> <a href="#setpgid">setpgid</a> <a href="#setpgrp">setpgrp</a> <a href="#setpriority">setpriority</a> <a href="#setsid">setsid</a> <a href="#uid">uid</a> <a href="#uid_eq">uid=</a> <a href="#wait">wait</a> <a href="#wait2">wait2</a> <a href="#waitpid">waitpid</a> <a href="#waitpid2">waitpid2</a> <p></p><hr>
<P></P>
  The <code>Process</code> module is a collection of methods used to manipulate 
  processes.
<P></P>
  <table border="0" width="100%" cellpadding="10"><tr><td valign="center" colspan="3" bgcolor="990066"><font color="white" size="6">
         constants
       </font></td></tr></table><table border="2" cellpadding="5">
<tr>
  <td valign="top"><tr>
       <td><a name="PRIO_PGRP"><code>PRIO_PGRP</code></a></td>
       <td>1</td>
       <td>Process Group priority.</td>
     </tr>
<P></P>
  <tr>
       <td><a name="PRIO_PROCESS"><code>PRIO_PROCESS</code></a></td>
       <td>0</td>
       <td>Process priority.</td>
     </tr>
<P></P>
  <tr>
       <td><a name="PRIO_USER"><code>PRIO_USER</code></a></td>
       <td>2</td>
       <td>User priority.</td>
     </tr>
<P></P>
  <tr>
       <td><a name="WNOHANG"><code>WNOHANG</code></a></td>
       <td>1</td>
       <td>Do not block if no child has exited. Not
    available on all platforms.</td>
     </tr>
<P></P>
  <tr>
       <td><a name="WUNTRACED"><code>WUNTRACED</code></a></td>
       <td>2</td>
       <td>Return stopped children as well. Not
    available on all platforms.</td>
     </tr>
</td>
</tr>
</table><p></p>
<P></P>
  <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="egid"><b>egid</b></a></font></td><td bgcolor="#ffaaaa">
        Process.egid 
        -> <i>aFixnum</i>
      </td></tr><td></td><td>
<P></P>
      Returns the effective group id for this process.
<P></P>

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

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="egid_eq"><b>egid=</b></a></font></td><td bgcolor="#ffaaaa">
        Process.egid= <i>aFixnum</i>
        -> <i>aFixnum</i>
      </td></tr><td></td><td>
<P></P>
            Sets the effective group id for this process.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="euid"><b>euid</b></a></font></td><td bgcolor="#ffaaaa">
        Process.euid 
        -> <i>aFixnum</i>
      </td></tr><td></td><td>
<P></P>
      Returns the effective user id for this process.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
  <td valign="top"><code>Process.euid</code></td>
  <td valign="top"></td>
  <td valign="top"><code>501</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="euid_eq"><b>euid=</b></a></font></td><td bgcolor="#ffaaaa">
        Process.euid= <i>aFixnum</i>
      </td></tr><td></td><td>
<P></P>
      Sets the effective user id for this process.  
      Not available on all platforms.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="exit_oh"><b>exit!</b></a></font></td><td bgcolor="#ffaaaa">
        Process.exit!( <i>aFixnum</i>=-1 )
      </td></tr><td></td><td>
<P></P>
            Exits the process immediately.      
      No exit handlers are run.
      <i>aFixnum</i> is returned to the underlying system as the exit
      status. 
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
Process.exit!(0)
</pre></td></tr></table>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="fork"><b>fork</b></a></font></td><td bgcolor="#ffaaaa">
        Process.fork <i>[</i>{ block }
<i>]</i>
        -> <i>aFixnum</i> or <code>nil</code>
      </td></tr><td></td><td>
<P></P>
      See <a href="ref_m_kernel.html#fork"><code>Kernel::fork</code></a> on page 420.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="getpgid"><b>getpgid</b></a></font></td><td bgcolor="#ffaaaa">
        Process.getpgid( <i>anInteger</i> )
        -> <i>anInteger</i>
      </td></tr><td></td><td>
<P></P>
      Returns the process group id for the given process id.
      Not available on all platforms.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
  <td valign="top"><code>Process.getpgid(Process.ppid())</code></td>
  <td valign="top"></td>
  <td valign="top"><code>13790</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="getpgrp"><b>getpgrp</b></a></font></td><td bgcolor="#ffaaaa">
        Process.getpgrp
        -> <i>anInteger</i>
      </td></tr><td></td><td>
<P></P>
      Returns the process group id for this process.
      Not available on all platforms.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
  <td valign="top"><code>Process.getpgid(0)</code></td>
  <td valign="top"></td>
  <td valign="top"><code>13790</code></td>
</tr>
<tr>
  <td valign="top"><code>Process.getpgrp</code></td>
  <td valign="top"></td>
  <td valign="top"><code>13790</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="getpriority"><b>getpriority</b></a></font></td><td bgcolor="#ffaaaa">
        Process.getpriority( <i>aKind</i>,
        <i>anInteger</i> ) -> <i>aFixnum</i>
      </td></tr><td></td><td>
<P></P>
      Gets the      
      scheduling priority for specified process, process group, or
      user.  <i>aKind</i> indicates the kind of entity to find:
      one of <a href="ref_m_process.html#PRIO_PGRP"><code>Process::PRIO_PGRP</code></a>,
      <a href="ref_m_process.html#PRIO_USER"><code>Process::PRIO_USER</code></a>, or <a href="ref_m_process.html#PRIO_PROCESS"><code>Process::PRIO_PROCESS</code></a>.
      <i>anInteger</i> is an id indicating the particular process,
      process group, or user (an id of 0 means <em>current</em>).
      Lower priorities are more favorable for
      scheduling.  Not available on all platforms.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
  <td valign="top"><code>Process.getpriority(Process::PRIO_USER,&nbsp;0)</code></td>
  <td valign="top"></td>
  <td valign="top"><code>0</code></td>
</tr>
<tr>
  <td valign="top"><code>Process.getpriority(Process::PRIO_PROCESS,&nbsp;0)</code></td>
  <td valign="top"></td>
  <td valign="top"><code>19</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="gid"><b>gid</b></a></font></td><td bgcolor="#ffaaaa">
        Process.gid 
        -> <i>aFixnum</i>
      </td></tr><td></td><td>
<P></P>
      Returns the group id for this process.
<P></P>

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

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="gid_eq"><b>gid=</b></a></font></td><td bgcolor="#ffaaaa">
        Process.gid= <i>aFixnum</i>
        -> <i>aFixnum</i>
      </td></tr><td></td><td>
<P></P>
            Sets the group id for this process.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="kill"><b>kill</b></a></font></td><td bgcolor="#ffaaaa">
        Process.kill( <i>aSignal</i>, 
        <i>[</i><i>aPid</i><i>]<sup>+</sup></i> ) -> <i>aFixnum</i>
      </td></tr><td></td><td>
<P></P>
      Sends the given signal to the specified process id(s),      
      or to the
      current process if <i>aPid</i> is zero.  <i>aSignal</i> may be an
      integer signal number or a POSIX signal name (either with or
      without a <code>SIG</code> prefix).  If <i>aSignal</i> is negative (or
      starts with a ``<code>-</code>'' sign), kills process groups instead
      of processes.  Not all signals are available on all platforms.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
trap("SIGHUP")&nbsp;{&nbsp;close_then_exit&nbsp;}
Process.kill("SIGHUP",&nbsp;0)
</pre></td></tr></table>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="pid"><b>pid</b></a></font></td><td bgcolor="#ffaaaa">
        Process.pid -> <i>aFixnum</i>
      </td></tr><td></td><td>
<P></P>
      Returns the process id of this process.
      Not available on all platforms.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
  <td valign="top"><code>Process.pid</code></td>
  <td valign="top"></td>
  <td valign="top"><code>16488</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="ppid"><b>ppid</b></a></font></td><td bgcolor="#ffaaaa">
        Process.ppid -> <i>aFixnum</i>
      </td></tr><td></td><td>
<P></P>
      Returns the process id of the parent of this process.
      Always returns 0 on NT.
      Not available on all platforms.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
print&nbsp;"I&nbsp;am&nbsp;",&nbsp;Process.pid,&nbsp;"\n"
Process.fork&nbsp;{&nbsp;print&nbsp;"Dad&nbsp;is&nbsp;",&nbsp;Process.ppid,&nbsp;"\n"&nbsp;}
</pre></td></tr></table>

<em>produces:</em>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
I&nbsp;am&nbsp;16490
Dad&nbsp;is&nbsp;16490
</pre></td></tr></table>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="setpgid"><b>setpgid</b></a></font></td><td bgcolor="#ffaaaa">
        Process.setpgid( <i>aPid</i>, <i>anInteger</i> )
        -> 0
      </td></tr><td></td><td>
<P></P>
            Sets the process group id of <i>aPid</i> (0 indicates this
      process) to <i>anInteger</i>.
      Not available on all platforms.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="setpgrp"><b>setpgrp</b></a></font></td><td bgcolor="#ffaaaa">
        Process.setpgrp
        -> 0
      </td></tr><td></td><td>
<P></P>
      Equivalent to <code>setpgid(0,0)</code>.
      Not available on all platforms.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="setpriority"><b>setpriority</b></a></font></td><td bgcolor="#ffaaaa">
        Process.setpriority( <i>kind</i>,
        <i>anInteger</i>, <i>anIntPriority</i> )
        -> 0
      </td></tr><td></td><td>
<P></P>
      See <a href="ref_m_process.html#getpriority"><code>Process#getpriority</code></a>.      
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
  <td valign="top"><code>Process.setpriority(Process::PRIO_USER,&nbsp;0,&nbsp;19)</code></td>
  <td valign="top"></td>
  <td valign="top"><code>0</code></td>
</tr>
<tr>
  <td valign="top"><code>Process.setpriority(Process::PRIO_PROCESS,&nbsp;0,&nbsp;19)</code></td>
  <td valign="top"></td>
  <td valign="top"><code>0</code></td>
</tr>
<tr>
  <td valign="top"><code>Process.getpriority(Process::PRIO_USER,&nbsp;0)</code></td>
  <td valign="top"></td>
  <td valign="top"><code>19</code></td>
</tr>
<tr>
  <td valign="top"><code>Process.getpriority(Process::PRIO_PROCESS,&nbsp;0)</code></td>
  <td valign="top"></td>
  <td valign="top"><code>19</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="setsid"><b>setsid</b></a></font></td><td bgcolor="#ffaaaa">
        Process.setsid
        -> <i>aFixnum</i>
      </td></tr><td></td><td>
<P></P>
      Establishes this process as a new session and process group      
      leader, with no controlling tty.
      Returns the session id.
      Not available on all platforms.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
  <td valign="top"><code>Process.setsid</code></td>
  <td valign="top"></td>
  <td valign="top"><code>16495</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="uid"><b>uid</b></a></font></td><td bgcolor="#ffaaaa">
        Process.uid
        -> <i>aFixnum</i>
      </td></tr><td></td><td>
<P></P>
      Returns the user id of this process.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
  <td valign="top"><code>Process.uid</code></td>
  <td valign="top"></td>
  <td valign="top"><code>501</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="uid_eq"><b>uid=</b></a></font></td><td bgcolor="#ffaaaa">
        Process.uid= <i>anInteger</i>
        -> <i>aNumeric</i>
      </td></tr><td></td><td>
<P></P>
      Sets the (integer) user id for this process.
      Not available on all platforms.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="wait"><b>wait</b></a></font></td><td bgcolor="#ffaaaa">
        Process.wait
        -> <i>aFixnum</i>
      </td></tr><td></td><td>
<P></P>
      Waits for any child process to exit and returns the process id
      of that child.      
      Raises a <code>SystemError</code> if there are no child processes.
      Not available on all platforms.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
  <td valign="top"><code>Process.fork&nbsp;{&nbsp;exit&nbsp;1;&nbsp;}</code></td>
  <td valign="top"></td>
  <td valign="top"><code>16500</code></td>
</tr>
<tr>
  <td valign="top"><code>Process.wait</code></td>
  <td valign="top"></td>
  <td valign="top"><code>16500</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="wait2"><b>wait2</b></a></font></td><td bgcolor="#ffaaaa">
        Process.wait2
        -> <i>anArray</i>
      </td></tr><td></td><td>
<P></P>
      Waits for any child process to exit and returns an array
      containing the process id and the exit status
      of that child.
      Raises a <code>SystemError</code> if there are no child processes.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
  <td valign="top"><code>Process.fork&nbsp;{&nbsp;exit&nbsp;1&nbsp;}</code></td>
  <td valign="top"></td>
  <td valign="top"><code>16503</code></td>
</tr>
<tr>
  <td valign="top"><code>Process.wait2</code></td>
  <td valign="top"></td>
  <td valign="top"><code>[16503,&nbsp;256]</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="waitpid"><b>waitpid</b></a></font></td><td bgcolor="#ffaaaa">
        Process.waitpid( <i>aPid</i>,
        <i>anInteger</i>=0 )
        -> <i>aPid</i>
      </td></tr><td></td><td>
<P></P>
      Waits for the given child process to exit. <i>anInteger</i> may be 
      a logical or of the flag value
      <a href="ref_m_process.html#WNOHANG"><code>Process::WNOHANG</code></a> (do not block if no child available)
      or <a href="ref_m_process.html#WUNTRACED"><code>Process::WUNTRACED</code></a> (return stopped children that haven't 
      been reported).
      Not all flags are available on all platforms, but a flag value
      of zero will work on all platforms.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>include&nbsp;Process</code></td>
</tr>
<tr>
  <td valign="top"><code>pid&nbsp;=&nbsp;fork&nbsp;{&nbsp;sleep&nbsp;3&nbsp;}</code></td>
  <td valign="top"></td>
  <td valign="top"><code>16506</code></td>
</tr>
<tr>
  <td valign="top"><code>Time.now</code></td>
  <td valign="top"></td>
  <td valign="top"><code>Sun&nbsp;Mar&nbsp;04&nbsp;23:31:14&nbsp;CST&nbsp;2001</code></td>
</tr>
<tr>
  <td valign="top"><code>waitpid(pid,&nbsp;Process::WNOHANG)</code></td>
  <td valign="top"></td>
  <td valign="top"><code>nil</code></td>
</tr>
<tr>
  <td valign="top"><code>Time.now</code></td>
  <td valign="top"></td>
  <td valign="top"><code>Sun&nbsp;Mar&nbsp;04&nbsp;23:31:14&nbsp;CST&nbsp;2001</code></td>
</tr>
<tr>
  <td valign="top"><code>waitpid(pid,&nbsp;0)</code></td>
  <td valign="top"></td>
  <td valign="top"><code>16506</code></td>
</tr>
<tr>
  <td valign="top"><code>Time.now</code></td>
  <td valign="top"></td>
  <td valign="top"><code>Sun&nbsp;Mar&nbsp;04&nbsp;23:31:17&nbsp;CST&nbsp;2001</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="waitpid2"><b>waitpid2</b></a></font></td><td bgcolor="#ffaaaa">
        Process.waitpid2( <i>aPid</i>,
        <i>anInteger</i>=0 )
        -> <i>anArray</i>
      </td></tr><td></td><td>
<P></P>
      Waits for the given child process to exit, returning that
      child's process id and exit status. <i>anInteger</i> may be 
      a logical or of the flag value
      <a href="ref_m_process.html#WNOHANG"><code>Process::WNOHANG</code></a> (do not block if no child available)
      or <a href="ref_m_process.html#WUNTRACED"><code>Process::WUNTRACED</code></a> (return stopped children that haven't 
      been reported).
      Not all flags are available on all platforms, but a flag value
      of zero will work on all platforms.
<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_m_objectspace.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"></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>.
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