441 lines
12 KiB
HTML
441 lines
12 KiB
HTML
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<meta name="Copyright" content="Copyright (c) 2006 by IBM Corporation">
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<title>kill()--Send Signal to Process or Group of Processes</title>
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<!-- US Government Users Restricted Rights -->
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<!-- Use, duplication or disclosure restricted by -->
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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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<!-- Begin Header Records ========================================== -->
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<!-- UNIX5 SCRIPT J converted by B2H R4.1 (346) (CMS) by V2KEA304 -->
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<!-- at RCHVMW2 on 17 Feb 1999 at 11:05:09 -->
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<!-- Edited by Kersten Feb 02 -->
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<!-- This file has undergone error condition cleanup on 04/30/02 by JET -->
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<!--End Header Records -->
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<link rel="stylesheet" type="text/css" href="../rzahg/ic.css">
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</head>
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<body>
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<a name="Top_Of_Page"></a>
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<!-- Java sync-link -->
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<script type="text/javascript" language="Javascript" src="../rzahg/synch.js">
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</script>
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<h2>kill()--Send Signal to Process or Group of Processes</h2>
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<div class="box" style="width: 60%;">
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<br>
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Syntax<br>
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<pre>
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#include <sys/types.h>
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#include <signal.h>
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int kill( pid_t <em>pid</em>, int <em>sig</em> );
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</pre>
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<br>
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Service Program Name: QPOSSRV1<br>
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<!-- iddvc RMBR -->
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<br>
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Default Public Authority: *USE<br>
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<!-- iddvc RMBR -->
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<br>
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Threadsafe: Yes<br>
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<!-- iddvc RMBR -->
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<br>
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</div>
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<p>The <strong>kill()</strong> function sends a signal to a process or process
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group specified by <em>pid</em>. The signal to be sent is specified by <em>
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sig</em> and is either 0 or one of the signals from the list in the
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<<strong>sys/signal.h</strong>> header file.</p>
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<p>The process sending the signal must have appropriate authority to the
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receiving process or processes. The <strong>kill()</strong> function is
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successful if the process has permission to send the signal <em>sig</em> to any
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of the processes specified by <em>pid</em>. If <strong>kill()</strong> is not
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successful, no signal is sent.</p>
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<p>A process can use <strong>kill()</strong> to send a signal to itself. If the
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signal is not blocked in the sending thread, and if no other thread has the
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<em>sig</em> unblocked or is waiting in a <em>sigwait</em> function for <em>
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sig</em>, either <em>sig</em> or at least one pending unblocked signal is
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delivered to the sender before <strong>kill()</strong> returns.</p>
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<br>
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<h3>Parameters</h3>
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<dl>
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<dt><strong><em>pid</em></strong></dt>
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<dd>(Input) The process ID or process group ID to receive the signal.<br>
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<br>
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</dd>
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<dt><strong><em>sig</em></strong></dt>
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<dd>(Input) The signal to be sent.</dd>
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</dl>
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<p><em>pid</em> and <em>sig</em> can be used as follows:</p>
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<table cellpadding="5">
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<!-- cols="10 90" -->
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<tr>
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<td align="left" valign="top" nowrap><em><samp>pid_t</samp></em> pid;</td>
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<td align="left" valign="top">Specifies the processes that the caller wants to
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send the signal to:
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<ul>
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<li>If <em>pid</em> is greater than zero, <strong>kill()</strong> sends the
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signal <em>sig</em> to the process whose ID is equal to <em>pid</em>.<br>
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<br>
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</li>
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<li>If <em>pid</em> is equal to zero, <strong>kill()</strong> sends the signal
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<em>sig</em> to all processes whose process group ID is equal to that of the
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sender, except for those to which the sender does not have the appropriate
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authority to send a signal.<br>
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<br>
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</li>
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<li>If <em>pid</em> is equal to -<samp>1</samp>, <strong>kill()</strong>
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returns -<samp>1</samp> and <em>errno</em> is set to [ESRCH].<br>
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<br>
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</li>
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<li>If <em>pid</em> is less than -<samp>1</samp>, <strong>kill()</strong> sends
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the signal <em>sig</em> to all processes whose process group ID is equal to the
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absolute value of <em>pid</em>, except for those to which the sender does not
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have appropriate authority to send a signal.</li>
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</ul>
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</td>
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</tr>
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<tr>
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<td align="left" valign="top"><em><samp>int</samp></em> sig;</td>
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<td align="left" valign="top">The signal that should be sent to the processes
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specified by <em>pid</em>. This must be zero, or one of the signals defined in
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the <<strong>sys/signal.h</strong>> header file. If <em>sig</em> is zero,
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<strong>kill()</strong> performs error checking, but does not send a signal.
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You can use a <em>sig</em> value of zero to check whether the <em>pid</em>
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argument is valid.</td>
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</tr>
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</table>
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<br>
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<br>
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<h3>Authorities</h3>
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<p>The thread sending the signal must have the appropriate authority to the
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receiving process. A thread is allowed to send a signal to a process if at
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least one of the following conditions is true:</p>
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<ul>
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<li>The thread is sending a signal to its own process.<br>
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<br>
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</li>
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<li>The thread has *JOBCTL special authority defined in the currently running
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user profile or in a current adopted user profile.<br>
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<br>
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</li>
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<li>The thread belongs to a process that is the parent of the receiving
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process. (The process being signaled has a <em>parent process ID</em> equal to
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the <em>process ID</em> of the thread sending the signal.)<br>
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<br>
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</li>
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<li>If the receiving process is multi-threaded,<br>
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<br>
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<ul>
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<li>The real or effective user ID of the thread matches the <em>job user
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identity</em> of the process receiving process (the process being
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signaled).</li>
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</ul>
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<br>
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</li>
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<li>Otherwise,<br>
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<br>
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<ul>
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<li>The real or effective user ID of the thread matches the real or effective
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user ID of the process being signaled. If _POSIX_SAVED_IDS is defined in the
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<<strong>unistd.h</strong>> include file, the saved set user ID of the
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intended recipient is checked instead of its effective user ID.</li>
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</ul>
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</li>
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</ul>
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<p>The <em>job user identity</em> is the name of the user profile by which a
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job is known to other jobs. It is described in more detail in the <a href=
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"../rzaks/rzaks1.htm">Work Management</a> topic.</p>
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<p>When sending a signal affects entries for multiple processes, the signal is
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generated for each process to which the process sending the signal is
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authorized. If the process does not have permission to send the signal to any
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receiving process, the [EPERM] error is returned.</p>
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<p>Regardless of user ID, a process can always send a SIGCONT signal to a
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process that is a member of the same process group (same <em>process group
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ID</em>) as the sender.</p>
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<br>
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<h3>Return Value</h3>
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<table cellpadding="5">
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<!-- cols="5 95" -->
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<tr>
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<td align="left" valign="top"><em>0</em></td>
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<td align="left" valign="top"><strong>kill()</strong> was successful. It had
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permission to send <em>sig</em> to one or more of the processes specified by
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<em>pid</em>.</td>
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</tr>
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<tr>
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<td align="left" valign="top"><em>-1</em></td>
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<td align="left" valign="top"><strong>kill()</strong> was not successful. It
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failed to send a signal. The <em>errno</em> variable is set to indicate the
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error.</td>
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</tr>
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</table>
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<br>
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<br>
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<h3>Error Conditions</h3>
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<p>If <strong>kill()</strong> is not successful, <em>errno</em> usually
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indicates one of the following errors. Under some conditions, <em>errno</em>
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could indicate an error other than those listed here.</p>
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<dl>
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<dt><em>[EINVAL]</em></dt>
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<dd>
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<p>The value specified for the argument is not correct.</p>
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<p>A function was passed incorrect argument values, or an operation was
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attempted on an object and the operation specified is not supported for that
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type of object.</p>
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<p>An argument value is not valid, out of range, or NULL.</p>
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<p>The value of <em>sig</em> is not within the range of signal numbers or is a
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signal that is not supported.</p>
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</dd>
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<dt><em>[ENOTSIGINIT]</em></dt>
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<dd>
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<p>Process not enabled for signals.</p>
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<p>An attempt was made to call a signal function under one of the following
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conditions:</p>
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<ul>
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<li>The signal function is being called for a process that is not enabled for
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asynchronous signals.<br>
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<br>
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</li>
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<li>The signal function is being called when the system signal controls have
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not been initialized.</li>
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</ul>
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<br>
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</dd>
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<dt><em>[ENOSYSRSC]</em></dt>
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<dd>
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<p>System resources not available to complete request.</p>
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</dd>
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<dt><em>[EPERM]</em></dt>
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<dd>Operation not permitted.
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<p>You must have appropriate privileges or be the owner of the object or other
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resource to do the requested operation.</p>
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</dd>
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<dt><em>[ESRCH]</em></dt>
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<dd>No item could be found that matches the specified value.
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<p>The process or process group specified in <em>pid</em> cannot be found.</p>
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</dd>
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</dl>
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<br>
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<h3>Usage Notes</h3>
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<ol>
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<li>If the value of <em>pid</em> is 0 (so that <strong>kill()</strong> is used
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to send a signal to all processes whose process group ID is equal to that of
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the sender), <strong>kill()</strong> enables the process for signals if the
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process is not already enabled for signals. For details, see <a href=
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"sigesig.htm">Qp0sEnableSignals()--Enable Process for Signals</a>.<br>
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<br>
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</li>
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<li>A process can use <strong>kill()</strong> to simulate the American National
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Standard C <strong>raise()</strong> function by using the following:
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<pre>
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sigset_t sigmask;
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/*
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* Allow all signals to be delivered by unblocking all signals
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*/
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sigemtyset( &sigmask );
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sigprocmask( SIG_SETMASK, &sigmask, NULL );
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...
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kill( getpid(), SIGUSR1 );
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</pre>
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<p>The example above ensures that no signals are blocked from delivery. When
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the <strong>kill()</strong> function is called, the behavior is the same as
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calling the <strong>raise()</strong> function.</p>
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</li>
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</ol>
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<br>
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<h3>Related Information</h3>
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<ul>
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<li>The <<strong>signal.h</strong>> file (see <a href="unix13.htm">Header
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Files for UNIX-Type Functions</a>)<br>
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<br>
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</li>
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<li>The <<strong>sys/types.h</strong>> file (see <a href="unix13.htm">
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Header Files for UNIX-Type Functions</a>)<br>
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<br>
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</li>
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<li><a href="sigdsig.htm">Qp0sDisableSignals()</a>--Disable Process for
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Signals<br>
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<br>
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</li>
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<li><a href="sigesig.htm">Qp0sEnableSignals()</a>--Enable Process for
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Signals<br>
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<br>
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</li>
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<li><a href="sigactn.htm">sigaction()</a>--Examine and Change Signal Action<br>
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<br>
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</li>
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<li><a href="sigtwait.htm">sigtimedwait()</a>--Synchronously Accept a Signal
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for Interval of Time<br>
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<br>
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</li>
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<li><a href="sigwait.htm">sigwait()</a>--Synchronously Accept a Signal<br>
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<br>
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</li>
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<li><a href="sigwaiti.htm">sigwaitinfo()</a>--Synchronously Accept a Signal and
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Signal Data</li>
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</ul>
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<br>
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<h3>Example</h3>
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<p>See <a href="../apiref/aboutapis.htm#codedisclaimer">Code disclaimer information</a>
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for information pertaining to code examples.</p>
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<p>The following example uses the <strong>kill()</strong> function:</p>
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<pre>
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#include <signal.h>
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#include <unistd.h>
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#include <errno.h>
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#include <stdio.h>
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#include <time.h>
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int sendsig( int );
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volatile int sigcount=0;
|
||
|
|
|
||
|
|
void catcher( int sig ) {
|
||
|
|
sigcount++;
|
||
|
|
}
|
||
|
|
|
||
|
|
int main( int argc, char *argv[] ) {
|
||
|
|
|
||
|
|
struct sigaction sigact;
|
||
|
|
int result;
|
||
|
|
|
||
|
|
/* set up a signal catching function to handle the signals */
|
||
|
|
/* that will be sent from the sendsig() function */
|
||
|
|
|
||
|
|
sigemptyset( &sigact.sa_mask );
|
||
|
|
sigact.sa_flags = 0;
|
||
|
|
sigact.sa_handler = catcher;
|
||
|
|
sigaction( SIGUSR1, &sigact, NULL );
|
||
|
|
|
||
|
|
/* Call the sendsig() function that will call the kill() */
|
||
|
|
/* function for SIGUSR1 n times based on the input value */
|
||
|
|
|
||
|
|
result = sendsig( 21 );
|
||
|
|
|
||
|
|
printf( "Back in main\n" );
|
||
|
|
printf( "The kill() function was called %d times\n", result );
|
||
|
|
printf( "The signal catching function was called %d times\n", \
|
||
|
|
sigcount );
|
||
|
|
|
||
|
|
return( 0 );
|
||
|
|
}
|
||
|
|
|
||
|
|
int sendsig( int count ) {
|
||
|
|
|
||
|
|
int i;
|
||
|
|
int j=0;
|
||
|
|
|
||
|
|
for( i=0; i < count; i++ ) {
|
||
|
|
if( i == ((i/10)*10) ) {
|
||
|
|
j++;
|
||
|
|
kill( getpid(), SIGUSR1 );
|
||
|
|
}
|
||
|
|
}
|
||
|
|
return( j );
|
||
|
|
}
|
||
|
|
</pre>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
<h3>Output:</h3>
|
||
|
|
|
||
|
|
<pre>
|
||
|
|
Back in main
|
||
|
|
The kill() function was called 3 times
|
||
|
|
The signal catching function was called 3 times
|
||
|
|
</pre>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
<hr>
|
||
|
|
API introduced: V3R6
|
||
|
|
|
||
|
|
<hr>
|
||
|
|
<center>
|
||
|
|
<table cellpadding="2" cellspacing="2">
|
||
|
|
<tr align="center">
|
||
|
|
<td valign="middle" align="center"><a href="#Top_Of_Page">Top</a> | <a href=
|
||
|
|
"unix.htm">UNIX-Type APIs</a> | <a href="aplist.htm">APIs by category</a></td>
|
||
|
|
</tr>
|
||
|
|
</table>
|
||
|
|
</center>
|
||
|
|
</body>
|
||
|
|
</html>
|
||
|
|
|