187 lines
6.5 KiB
HTML
187 lines
6.5 KiB
HTML
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<title>waitid</title>
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<basefont size="3"> <a name="waitid"></a> <a name="tag_03_823"></a><!-- waitid -->
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<!--header start-->
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<center><font size="2">The Open Group Base Specifications Issue 6<br>
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IEEE Std 1003.1-2001<br>
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Copyright © 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
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<!--header end-->
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<hr size="2" noshade>
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<h4><a name="tag_03_823_01"></a>NAME</h4>
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<blockquote>waitid - wait for a child process to change state</blockquote>
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<h4><a name="tag_03_823_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<div class="box"><code><tt><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt=
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"[Option Start]" border="0"> #include <<a href="../basedefs/sys/wait.h.html">sys/wait.h</a>><br>
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<br>
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int waitid(idtype_t</tt> <i>idtype</i><tt>, id_t</tt> <i>id</i><tt>, siginfo_t *</tt><i>infop</i><tt>, int</tt>
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<i>options</i><tt>); <img src="../images/opt-end.gif" alt="[Option End]" border="0"></tt></code></div>
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<tt><br>
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</tt></blockquote>
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<h4><a name="tag_03_823_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>waitid</i>() function shall suspend the calling thread until one child of the process containing the calling thread
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changes state. It records the current state of a child in the structure pointed to by <i>infop</i>. If a child process changed
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state prior to the call to <i>waitid</i>(), <i>waitid</i>() shall return immediately. If more than one thread is suspended in <a
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href="../functions/wait.html"><i>wait</i>()</a> or <a href="../functions/waitpid.html"><i>waitpid</i>()</a> waiting for termination
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of the same process, exactly one thread shall return the process status at the time of the target process termination.</p>
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<p>The <i>idtype</i> and <i>id</i> arguments are used to specify which children <i>waitid</i>() waits for.</p>
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<p>If <i>idtype</i> is P_PID, <i>waitid</i>() shall wait for the child with a process ID equal to (<b>pid_t</b>)<i>id</i>.</p>
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<p>If <i>idtype</i> is P_PGID, <i>waitid</i>() shall wait for any child with a process group ID equal to
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(<b>pid_t</b>)<i>id</i>.</p>
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<p>If <i>idtype</i> is P_ALL, <i>waitid</i>() shall wait for any children and <i>id</i> is ignored.</p>
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<p>The <i>options</i> argument is used to specify which state changes <i>waitid</i>() shall wait for. It is formed by OR'ing
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together one or more of the following flags:</p>
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<dl compact>
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<dt>WEXITED</dt>
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<dd>Wait for processes that have exited.</dd>
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<dt>WSTOPPED</dt>
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<dd>Status shall be returned for any child that has stopped upon receipt of a signal.</dd>
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<dt>WCONTINUED</dt>
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<dd>Status shall be returned for any child that was stopped and has been continued.</dd>
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<dt>WNOHANG</dt>
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<dd>Return immediately if there are no children to wait for.</dd>
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<dt>WNOWAIT</dt>
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<dd>Keep the process whose status is returned in <i>infop</i> in a waitable state. This shall not affect the state of the process;
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the process may be waited for again after this call completes.</dd>
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</dl>
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<p>The application shall ensure that the <i>infop</i> argument points to a <b>siginfo_t</b> structure. If <i>waitid</i>() returns
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because a child process was found that satisfied the conditions indicated by the arguments <i>idtype</i> and <i>options</i>, then
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the structure pointed to by <i>infop</i> shall be filled in by the system with the status of the process. The <i>si_signo</i>
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member shall always be equal to SIGCHLD.</p>
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</blockquote>
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<h4><a name="tag_03_823_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>If WNOHANG was specified and there are no children to wait for, 0 shall be returned. If <i>waitid</i>() returns due to the
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change of state of one of its children, 0 shall be returned. Otherwise, -1 shall be returned and <i>errno</i> set to indicate the
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error.</p>
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</blockquote>
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<h4><a name="tag_03_823_05"></a>ERRORS</h4>
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<blockquote>
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<p>The <i>waitid</i>() function shall fail if:</p>
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<dl compact>
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<dt>[ECHILD]</dt>
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<dd>The calling process has no existing unwaited-for child processes.</dd>
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<dt>[EINTR]</dt>
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<dd>The <i>waitid</i>() function was interrupted by a signal.</dd>
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<dt>[EINVAL]</dt>
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<dd>An invalid value was specified for <i>options</i>, or <i>idtype</i> and <i>id</i> specify an invalid set of processes.</dd>
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</dl>
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</blockquote>
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<hr>
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<div class="box"><em>The following sections are informative.</em></div>
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<h4><a name="tag_03_823_06"></a>EXAMPLES</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_823_07"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_823_08"></a>RATIONALE</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_823_09"></a>FUTURE DIRECTIONS</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_823_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="exec.html"><i><a href="../functions/exec.html">exec</a></i>()</a> , <a href="exit.html"><i>exit</i>()</a> , <a href=
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"wait.html"><i>wait</i>()</a> , the Base Definitions volume of IEEE Std 1003.1-2001, <a href=
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"../basedefs/sys/wait.h.html"><i><sys/wait.h></i></a></p>
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</blockquote>
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<h4><a name="tag_03_823_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 4, Version 2.</p>
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</blockquote>
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<h4><a name="tag_03_823_12"></a>Issue 5</h4>
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<blockquote>
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<p>Moved from X/OPEN UNIX extension to BASE.</p>
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<p>The DESCRIPTION is updated for alignment with the POSIX Threads Extension.</p>
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</blockquote>
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<h4><a name="tag_03_823_13"></a>Issue 6</h4>
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<blockquote>
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<p>The DESCRIPTION is updated to avoid use of the term "must" for application requirements.</p>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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