148 lines
5.8 KiB
HTML
148 lines
5.8 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<meta name="generator" content="HTML Tidy, see www.w3.org">
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<link type="text/css" rel="stylesheet" href="style.css"><!-- Generated by The Open Group's rhtm tool v1.2.1 -->
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<!-- Copyright (c) 2001 The Open Group, All Rights Reserved -->
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<title>setsid</title>
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<body bgcolor="white">
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<basefont size="3"> <a name="setsid"></a> <a name="tag_03_667"></a><!-- setsid -->
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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_667_01"></a>NAME</h4>
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<blockquote>setsid - create session and set process group ID</blockquote>
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<h4><a name="tag_03_667_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<p><code><tt>#include <<a href="../basedefs/unistd.h.html">unistd.h</a>><br>
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<br>
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pid_t setsid(void);<br>
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</tt></code></p>
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</blockquote>
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<h4><a name="tag_03_667_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>setsid</i>() function shall create a new session, if the calling process is not a process group leader. Upon return the
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calling process shall be the session leader of this new session, shall be the process group leader of a new process group, and
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shall have no controlling terminal. The process group ID of the calling process shall be set equal to the process ID of the calling
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process. The calling process shall be the only process in the new process group and the only process in the new session.</p>
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</blockquote>
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<h4><a name="tag_03_667_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>Upon successful completion, <i>setsid</i>() shall return the value of the new process group ID of the calling process.
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Otherwise, it shall return (<b>pid_t</b>)-1 and set <i>errno</i> to indicate the error.</p>
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</blockquote>
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<h4><a name="tag_03_667_05"></a>ERRORS</h4>
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<blockquote>
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<p>The <i>setsid</i>() function shall fail if:</p>
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<dl compact>
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<dt>[EPERM]</dt>
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<dd>The calling process is already a process group leader, or the process group ID of a process other than the calling process
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matches the process ID of the calling process.</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_667_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_667_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_667_08"></a>RATIONALE</h4>
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<blockquote>
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<p>The <i>setsid</i>() function is similar to the <a href="../functions/setpgrp.html"><i>setpgrp</i>()</a> function of System V.
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System V, without job control, groups processes into process groups and creates new process groups via <a href=
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"../functions/setpgrp.html"><i>setpgrp</i>()</a>; only one process group may be part of a login session.</p>
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<p>Job control allows multiple process groups within a login session. In order to limit job control actions so that they can only
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affect processes in the same login session, this volume of IEEE Std 1003.1-2001 adds the concept of a session that is
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created via <i>setsid</i>(). The <i>setsid</i>() function also creates the initial process group contained in the session.
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Additional process groups can be created via the <a href="../functions/setpgid.html"><i>setpgid</i>()</a> function. A System V
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process group would correspond to a POSIX System Interfaces session containing a single POSIX process group. Note that this
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function requires that the calling process not be a process group leader. The usual way to ensure this is true is to create a new
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process with <a href="../functions/fork.html"><i>fork</i>()</a> and have it call <i>setsid</i>(). The <a href=
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"../functions/fork.html"><i>fork</i>()</a> function guarantees that the process ID of the new process does not match any existing
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process group ID.</p>
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</blockquote>
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<h4><a name="tag_03_667_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_667_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="getsid.html"><i>getsid</i>()</a> , <a href="setpgid.html"><i>setpgid</i>()</a> , <a href=
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"setpgrp.html"><i>setpgrp</i>()</a> , the Base Definitions volume of IEEE Std 1003.1-2001, <a href=
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"../basedefs/sys/types.h.html"><i><sys/types.h></i></a>, <a href="../basedefs/unistd.h.html"><i><unistd.h></i></a></p>
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</blockquote>
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<h4><a name="tag_03_667_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 3. Included for alignment with the POSIX.1-1988 standard.</p>
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</blockquote>
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<h4><a name="tag_03_667_12"></a>Issue 6</h4>
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<blockquote>
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<p>In the SYNOPSIS, the optional include of the <a href="../basedefs/sys/types.h.html"><i><sys/types.h></i></a> header is
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removed.</p>
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<p>The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:</p>
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<ul>
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<li>
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<p>The requirement to include <a href="../basedefs/sys/types.h.html"><i><sys/types.h></i></a> has been removed. Although <a
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href="../basedefs/sys/types.h.html"><i><sys/types.h></i></a> was required for conforming implementations of previous POSIX
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specifications, it was not required for UNIX applications.</p>
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</li>
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</ul>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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UNIX ® is a registered Trademark of The Open Group.<br>
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POSIX ® is a registered Trademark of The IEEE.<br>
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"../utilities/contents.html">XCU</a> | <a href="../functions/contents.html">XSH</a> | <a href="../xrat/contents.html">XRAT</a>
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