479 lines
9.9 KiB
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479 lines
9.9 KiB
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of SETPGID</TITLE>
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</HEAD><BODY>
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<H1>SETPGID</H1>
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Section: Linux Programmer's Manual (2)<BR>Updated: 2017-09-15<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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setpgid, getpgid, setpgrp, getpgrp - set/get process group
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<B>#include <<A HREF="file:///usr/include/sys/types.h">sys/types.h</A>></B>
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<BR>
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<B>#include <<A HREF="file:///usr/include/unistd.h">unistd.h</A>></B>
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<P>
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<B>int setpgid(pid_t </B><I>pid</I><B>, pid_t </B><I>pgid</I><B>);</B>
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<BR>
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<B>pid_t getpgid(pid_t </B><I>pid</I><B>);</B>
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<P>
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<B>pid_t getpgrp(void);</B> /* POSIX.1 version */
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<BR>
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<B>pid_t getpgrp(pid_t </B><I>pid</I><B>); </B>
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/* BSD version */
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<P>
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<B>int setpgrp(void);</B> /* System V version */
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<BR>
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<B>int setpgrp(pid_t </B><I>pid</I><B>, pid_t </B><I>pgid</I><B>); </B>
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/* BSD version */
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<P>
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Feature Test Macro Requirements for glibc (see
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<B><A HREF="/cgi-bin/man/man2html?7+feature_test_macros">feature_test_macros</A></B>(7)):
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<P>
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<B>getpgid</B>():
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<DL COMPACT><DT id="1"><DD>
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_XOPEN_SOURCE >= 500
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<BR>
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<BR> || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L
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</DL>
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<P>
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<B>setpgrp</B>() (POSIX.1):
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<PRE>
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_XOPEN_SOURCE >= 500
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|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
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|| /* Glibc versions <= 2.19: */ _SVID_SOURCE
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</PRE>
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<P>
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<B>setpgrp</B>() (BSD),
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<B>getpgrp</B>() (BSD):
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<PRE>
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[These are available only before glibc 2.19]
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_BSD_SOURCE &&
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! (_POSIX_SOURCE || _POSIX_C_SOURCE || _XOPEN_SOURCE ||
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_GNU_SOURCE || _SVID_SOURCE)
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</PRE>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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All of these interfaces are available on Linux,
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and are used for getting and setting the
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process group ID (PGID) of a process.
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The preferred, POSIX.1-specified ways of doing this are:
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<B>getpgrp</B>(void),
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for retrieving the calling process's PGID; and
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<B>setpgid</B>(),
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for setting a process's PGID.
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<P>
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<B>setpgid</B>()
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sets the PGID of the process specified by
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<I>pid</I>
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to
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<I>pgid</I>.
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If
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<I>pid</I>
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is zero, then the process ID of the calling process is used.
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If
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<I>pgid</I>
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is zero, then the PGID of the process specified by
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<I>pid</I>
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is made the same as its process ID.
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If
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<B>setpgid</B>()
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is used to move a process from one process
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group to another (as is done by some shells when creating pipelines),
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both process groups must be part of the same session (see
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<B><A HREF="/cgi-bin/man/man2html?2+setsid">setsid</A></B>(2)
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and
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<B><A HREF="/cgi-bin/man/man2html?7+credentials">credentials</A></B>(7)).
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In this case,
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the <I>pgid</I> specifies an existing process group to be joined and the
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session ID of that group must match the session ID of the joining process.
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<P>
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The POSIX.1 version of
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<B>getpgrp</B>(),
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which takes no arguments,
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returns the PGID of the calling process.
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<P>
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<B>getpgid</B>()
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returns the PGID of the process specified by
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<I>pid</I>.
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If
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<I>pid</I>
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is zero, the process ID of the calling process is used.
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(Retrieving the PGID of a process other than the caller is rarely
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necessary, and the POSIX.1
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<B>getpgrp</B>()
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is preferred for that task.)
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<P>
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The System V-style
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<B>setpgrp</B>(),
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which takes no arguments, is equivalent to
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<I>setpgid(0, 0)</I>.
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<P>
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The BSD-specific
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<B>setpgrp</B>()
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call, which takes arguments
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<I>pid</I>
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and
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<I>pgid</I>,
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is a wrapper function that calls
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<P>
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<BR> setpgid(pid, pgid)
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<P>
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Since glibc 2.19, the BSD-specific
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<B>setpgrp</B>()
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function is no longer exposed by
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<I><<A HREF="file:///usr/include/unistd.h">unistd.h</A>></I>;
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calls should be replaced with the
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<B>setpgid</B>()
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call shown above.
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<P>
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The BSD-specific
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<B>getpgrp</B>()
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call, which takes a single
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<I>pid</I>
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argument, is a wrapper function that calls
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<P>
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<BR> getpgid(pid)
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<P>
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Since glibc 2.19, the BSD-specific
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<B>getpgrp</B>()
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function is no longer exposed by
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<I><<A HREF="file:///usr/include/unistd.h">unistd.h</A>></I>;
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calls should be replaced with calls to the POSIX.1
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<B>getpgrp</B>()
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which takes no arguments (if the intent is to obtain the caller's PGID),
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or with the
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<B>getpgid</B>()
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call shown above.
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<A NAME="lbAE"> </A>
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<H2>RETURN VALUE</H2>
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On success,
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<B>setpgid</B>()
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and
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<B>setpgrp</B>()
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return zero.
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On error, -1 is returned, and
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<I>errno</I>
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is set appropriately.
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<P>
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The POSIX.1
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<B>getpgrp</B>()
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always returns the PGID of the caller.
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<P>
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<B>getpgid</B>(),
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and the BSD-specific
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<B>getpgrp</B>()
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return a process group on success.
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On error, -1 is returned, and
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<I>errno</I>
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is set appropriately.
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<A NAME="lbAF"> </A>
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<H2>ERRORS</H2>
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<DL COMPACT>
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<DT id="2"><B>EACCES</B>
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<DD>
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An attempt was made to change the process group ID
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of one of the children of the calling process and the child had
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already performed an
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<B><A HREF="/cgi-bin/man/man2html?2+execve">execve</A></B>(2)
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(<B>setpgid</B>(),
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<B>setpgrp</B>()).
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<DT id="3"><B>EINVAL</B>
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<DD>
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<I>pgid</I>
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is less than 0
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(<B>setpgid</B>(),
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<B>setpgrp</B>()).
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<DT id="4"><B>EPERM</B>
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<DD>
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An attempt was made to move a process into a process group in a
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different session, or to change the process
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group ID of one of the children of the calling process and the
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child was in a different session, or to change the process group ID of
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a session leader
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(<B>setpgid</B>(),
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<B>setpgrp</B>()).
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<DT id="5"><B>ESRCH</B>
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<DD>
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For
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<B>getpgid</B>():
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<I>pid</I>
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does not match any process.
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For
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<B>setpgid</B>():
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<I>pid</I>
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is not the calling process and not a child of the calling process.
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</DL>
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<A NAME="lbAG"> </A>
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<H2>CONFORMING TO</H2>
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<B>setpgid</B>()
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and the version of
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<B>getpgrp</B>()
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with no arguments
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conform to POSIX.1-2001.
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<P>
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POSIX.1-2001 also specifies
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<B>getpgid</B>()
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and the version of
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<B>setpgrp</B>()
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that takes no arguments.
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(POSIX.1-2008 marks this
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<B>setpgrp</B>()
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specification as obsolete.)
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<P>
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The version of
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<B>getpgrp</B>()
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with one argument and the version of
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<B>setpgrp</B>()
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that takes two arguments derive from 4.2BSD,
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and are not specified by POSIX.1.
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<A NAME="lbAH"> </A>
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<H2>NOTES</H2>
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A child created via
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<B><A HREF="/cgi-bin/man/man2html?2+fork">fork</A></B>(2)
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inherits its parent's process group ID.
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The PGID is preserved across an
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<B><A HREF="/cgi-bin/man/man2html?2+execve">execve</A></B>(2).
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<P>
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Each process group is a member of a session and each process is a
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member of the session of which its process group is a member.
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(See
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<B><A HREF="/cgi-bin/man/man2html?7+credentials">credentials</A></B>(7).)
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<P>
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A session can have a controlling terminal.
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At any time, one (and only one) of the process groups
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in the session can be the foreground process group
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for the terminal;
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the remaining process groups are in the background.
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If a signal is generated from the terminal (e.g., typing the
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interrupt key to generate
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<B>SIGINT</B>),
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that signal is sent to the foreground process group.
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(See
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<B><A HREF="/cgi-bin/man/man2html?3+termios">termios</A></B>(3)
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for a description of the characters that generate signals.)
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Only the foreground process group may
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<B><A HREF="/cgi-bin/man/man2html?2+read">read</A></B>(2)
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from the terminal;
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if a background process group tries to
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<B><A HREF="/cgi-bin/man/man2html?2+read">read</A></B>(2)
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from the terminal, then the group is sent a
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<B>SIGTTIN</B>
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signal, which suspends it.
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The
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<B><A HREF="/cgi-bin/man/man2html?3+tcgetpgrp">tcgetpgrp</A></B>(3)
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and
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<B><A HREF="/cgi-bin/man/man2html?3+tcsetpgrp">tcsetpgrp</A></B>(3)
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functions are used to get/set the foreground
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process group of the controlling terminal.
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<P>
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The
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<B>setpgid</B>()
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and
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<B>getpgrp</B>()
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calls are used by programs such as
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<B><A HREF="/cgi-bin/man/man2html?1+bash">bash</A></B>(1)
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to create process groups in order to implement shell job control.
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<P>
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If the termination of a process causes a process group to become orphaned,
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and if any member of the newly orphaned process group is stopped, then a
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<B>SIGHUP</B>
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signal followed by a
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<B>SIGCONT</B>
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signal will be sent to each process
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in the newly orphaned process group.
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An orphaned process group is one in which the parent of
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every member of process group is either itself also a member
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of the process group or is a member of a process group
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in a different session (see also
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<B><A HREF="/cgi-bin/man/man2html?7+credentials">credentials</A></B>(7)).
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<A NAME="lbAI"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?2+getuid">getuid</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+setsid">setsid</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?3+tcgetpgrp">tcgetpgrp</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+tcsetpgrp">tcsetpgrp</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+termios">termios</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?7+credentials">credentials</A></B>(7)
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<A NAME="lbAJ"> </A>
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<H2>COLOPHON</H2>
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This page is part of release 5.05 of the Linux
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<I>man-pages</I>
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project.
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A description of the project,
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information about reporting bugs,
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and the latest version of this page,
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can be found at
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<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="6"><A HREF="#lbAB">NAME</A><DD>
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<DT id="7"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="8"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="9"><A HREF="#lbAE">RETURN VALUE</A><DD>
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<DT id="10"><A HREF="#lbAF">ERRORS</A><DD>
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<DT id="11"><A HREF="#lbAG">CONFORMING TO</A><DD>
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<DT id="12"><A HREF="#lbAH">NOTES</A><DD>
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<DT id="13"><A HREF="#lbAI">SEE ALSO</A><DD>
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<DT id="14"><A HREF="#lbAJ">COLOPHON</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:05:34 GMT, March 31, 2021
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</BODY>
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</HTML>
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