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+.\" and Copyright (C) 2007, Michael Kerrisk <mtk.manpages@gmail.com>
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.\" @(#)getpgrp.2 6.4 (Berkeley) 3/10/91
.\"
.\" Modified 1996-07-21 by Andries Brouwer <aeb@cwi.nl>
.\" Modified 1996-11-06 by Eric S. Raymond <esr@thyrsus.com>
.\" Modified 1999-09-02 by Michael Haardt <michael@moria.de>
-.\" Modified 2002-01-18 by Michael Kerrisk <mtk-manpages@gmx.net>
+.\" Modified 2002-01-18 by Michael Kerrisk <mtk.manpages@gmail.com>
.\" Modified 2003-01-20 by Andries Brouwer <aeb@cwi.nl>
+.\" 2007-07-25, mtk, fairly substantial rewrites and rearrangements
+.\" of text.
.\"
-.TH SETPGID 2 2003-01-20 "Linux" "Linux Programmer's Manual"
+.TH SETPGID 2 2017-09-15 "Linux" "Linux Programmer's Manual"
.SH NAME
setpgid, getpgid, setpgrp, getpgrp \- set/get process group
.SH SYNOPSIS
+.B #include <sys/types.h>
+.br
.B #include <unistd.h>
-.sp
+.PP
.BI "int setpgid(pid_t " pid ", pid_t " pgid );
.br
.BI "pid_t getpgid(pid_t " pid );
+.PP
+.BR "pid_t getpgrp(void);" " /* POSIX.1 version */"
+.br
+.BI "pid_t getpgrp(pid_t " pid ");\ \ \ \ \ \ \ \ \ \ \ "
+/* BSD version */
+.PP
+.BR "int setpgrp(void);" " /* System V version */"
.br
-.B int setpgrp(void);
+.BI "int setpgrp(pid_t " pid ", pid_t " pgid ");\ "
+/* BSD version */
+.PP
+.in -4n
+Feature Test Macro Requirements for glibc (see
+.BR feature_test_macros (7)):
+.in
+.PP
+.ad l
+.BR getpgid ():
+.RS 4
+_XOPEN_SOURCE\ >=\ 500
+.\" || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
.br
-.B pid_t getpgrp(void);
+ || /* Since glibc 2.12: */ _POSIX_C_SOURCE\ >=\ 200809L
+.RE
+.PP
+.BR setpgrp "() (POSIX.1):"
+.nf
+ _XOPEN_SOURCE\ >=\ 500
+.\" || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
+ || /* Since glibc 2.19: */ _DEFAULT_SOURCE
+ || /* Glibc versions <= 2.19: */ _SVID_SOURCE
+.fi
+.PP
+.BR setpgrp "()\ (BSD),"
+.BR getpgrp "()\ (BSD):"
+.nf
+ [These are available only before glibc 2.19]
+ _BSD_SOURCE &&
+ !\ (_POSIX_SOURCE || _POSIX_C_SOURCE || _XOPEN_SOURCE ||
+ _GNU_SOURCE || _SVID_SOURCE)
+.fi
+.ad
.SH DESCRIPTION
+All of these interfaces are available on Linux,
+and are used for getting and setting the
+process group ID (PGID) of a process.
+The preferred, POSIX.1-specified ways of doing this are:
+.BR getpgrp (void),
+for retrieving the calling process's PGID; and
+.BR setpgid (),
+for setting a process's PGID.
+.PP
.BR setpgid ()
-sets the process group ID of the process specified by
+sets the PGID of the process specified by
.I pid
to
.IR pgid .
If
.I pid
-is zero, the process ID of the current process is used. If
+is zero, then the process ID of the calling process is used.
+If
.I pgid
-is zero, the process ID of the process specified by
+is zero, then the PGID of the process specified by
.I pid
-is used. If \fBsetpgid\fP() is used to move a process from one process
+is made the same as its process ID.
+If
+.BR setpgid ()
+is used to move a process from one process
group to another (as is done by some shells when creating pipelines),
-both process groups must be part of the same session. In this case,
+both process groups must be part of the same session (see
+.BR setsid (2)
+and
+.BR credentials (7)).
+In this case,
the \fIpgid\fP specifies an existing process group to be joined and the
session ID of that group must match the session ID of the joining process.
-
+.PP
+The POSIX.1 version of
+.BR getpgrp (),
+which takes no arguments,
+returns the PGID of the calling process.
+.PP
.BR getpgid ()
-returns the process group ID of the process specified by
+returns the PGID of the process specified by
.IR pid .
If
.I pid
-is zero, the process ID of the current process is used.
-
-The call
-.BR setpgrp ()
-is equivalent to
-.BR setpgid(0,0) .
-
-Similarly,
+is zero, the process ID of the calling process is used.
+(Retrieving the PGID of a process other than the caller is rarely
+necessary, and the POSIX.1
.BR getpgrp ()
-is equivalent to
-.BR getpgid(0) .
-Each process group is a member of a session and each process is a
-member of the session of which its process group is a member.
-
-Process groups are used for distribution of signals, and by terminals to
-arbitrate requests for their input: Processes that have the same process
-group as the terminal are foreground and may read, while others will
-block with a signal if they attempt to read.
-These calls are thus used by programs such as
-.BR csh (1)
-to create process groups in implementing job control. The
-.B TIOCGPGRP
+is preferred for that task.)
+.PP
+The System\ V-style
+.BR setpgrp (),
+which takes no arguments, is equivalent to
+.IR "setpgid(0,\ 0)" .
+.PP
+The BSD-specific
+.BR setpgrp ()
+call, which takes arguments
+.I pid
and
-.B TIOCSPGRP
-calls described in
-.BR termios (3)
-are used to get/set the process group of the control terminal.
-
-If a session has a controlling terminal, CLOCAL is not set and a hangup
-occurs, then the session leader is sent a SIGHUP. If the session leader
-exits, the SIGHUP signal will be sent to each process in the foreground
-process group of the controlling terminal.
-
-If the exit of the process causes a process group to become orphaned,
-and if any member of the newly-orphaned process group is stopped, then a
-SIGHUP signal followed by a SIGCONT signal will be sent to each process
-in the newly-orphaned process group.
-
-.SH "RETURN VALUE"
+.IR pgid ,
+is a wrapper function that calls
+.PP
+ setpgid(pid, pgid)
+.PP
+.\" The true BSD setpgrp() system call differs in allowing the PGID
+.\" to be set to arbitrary values, rather than being restricted to
+.\" PGIDs in the same session.
+Since glibc 2.19, the BSD-specific
+.BR setpgrp ()
+function is no longer exposed by
+.IR <unistd.h> ;
+calls should be replaced with the
+.BR setpgid ()
+call shown above.
+.PP
+The BSD-specific
+.BR getpgrp ()
+call, which takes a single
+.I pid
+argument, is a wrapper function that calls
+.PP
+ getpgid(pid)
+.PP
+Since glibc 2.19, the BSD-specific
+.BR getpgrp ()
+function is no longer exposed by
+.IR <unistd.h> ;
+calls should be replaced with calls to the POSIX.1
+.BR getpgrp ()
+which takes no arguments (if the intent is to obtain the caller's PGID),
+or with the
+.BR getpgid ()
+call shown above.
+.SH RETURN VALUE
On success,
.BR setpgid ()
-and
+and
.BR setpgrp ()
-return zero. On error, \-1 is returned, and
+return zero.
+On error, \-1 is returned, and
.I errno
is set appropriately.
-
-.BR getpgid ()
-returns a process group on success.
+.PP
+The POSIX.1
+.BR getpgrp ()
+always returns the PGID of the caller.
+.PP
+.BR getpgid (),
+and the BSD-specific
+.BR getpgrp ()
+return a process group on success.
On error, \-1 is returned, and
.I errno
is set appropriately.
-
-.BR getpgrp ()
-always returns the current process group.
.SH ERRORS
.TP
.B EACCES
An attempt was made to change the process group ID
of one of the children of the calling process and the child had
-already performed an \fBexecve\fP()
-(\fBsetpgid\fP(), \fBsetpgrp\fP()).
+already performed an
+.BR execve (2)
+.RB ( setpgid (),
+.BR setpgrp ()).
.TP
.B EINVAL
.I pgid
is less than 0
-(\fBsetpgid\fP(), \fBsetpgrp\fP()).
+.RB ( setpgid (),
+.BR setpgrp ()).
.TP
.B EPERM
-An attempt was made to move a process into a process group in a
-different session, or to change the process
-group ID of one of the children of the calling process and the
+An attempt was made to move a process into a process group in a
+different session, or to change the process
+group ID of one of the children of the calling process and the
child was in a different session, or to change the process group ID of
a session leader
-(\fBsetpgid\fP(), \fBsetpgrp\fP()).
+.RB ( setpgid (),
+.BR setpgrp ()).
.TP
.B ESRCH
For
For
.BR setpgid ():
.I pid
-is not the current process and not a child of the current process.
-.SH "CONFORMING TO"
-The functions
+is not the calling process and not a child of the calling process.
+.SH CONFORMING TO
.BR setpgid ()
-and
+and the version of
.BR getpgrp ()
-conform to POSIX.1.
-The function
-.BR setpgrp ()
-is from 4.2BSD.
-The function
+with no arguments
+conform to POSIX.1-2001.
+.PP
+POSIX.1-2001 also specifies
.BR getpgid ()
-conforms to SVr4.
+and the version of
+.BR setpgrp ()
+that takes no arguments.
+(POSIX.1-2008 marks this
+.BR setpgrp ()
+specification as obsolete.)
+.PP
+The version of
+.BR getpgrp ()
+with one argument and the version of
+.BR setpgrp ()
+that takes two arguments derive from 4.2BSD,
+and are not specified by POSIX.1.
.SH NOTES
-POSIX took
+A child created via
+.BR fork (2)
+inherits its parent's process group ID.
+The PGID is preserved across an
+.BR execve (2).
+.PP
+Each process group is a member of a session and each process is a
+member of the session of which its process group is a member.
+(See
+.BR credentials (7).)
+.PP
+A session can have a controlling terminal.
+At any time, one (and only one) of the process groups
+in the session can be the foreground process group
+for the terminal;
+the remaining process groups are in the background.
+If a signal is generated from the terminal (e.g., typing the
+interrupt key to generate
+.BR SIGINT ),
+that signal is sent to the foreground process group.
+(See
+.BR termios (3)
+for a description of the characters that generate signals.)
+Only the foreground process group may
+.BR read (2)
+from the terminal;
+if a background process group tries to
+.BR read (2)
+from the terminal, then the group is sent a
+.B SIGTTIN
+signal, which suspends it.
+The
+.BR tcgetpgrp (3)
+and
+.BR tcsetpgrp (3)
+functions are used to get/set the foreground
+process group of the controlling terminal.
+.PP
+The
.BR setpgid ()
-from the BSD function
-.BR setpgrp ().
-Also System V has a function with the same name, but it is identical to
-.BR setsid (2).
-.LP
-To get the prototypes under glibc, define both _XOPEN_SOURCE and
-_XOPEN_SOURCE_EXTENDED, or use "#define _XOPEN_SOURCE \fIn\fP"
-for some integer \fIn\fP larger than or equal to 500.
-.SH "SEE ALSO"
+and
+.BR getpgrp ()
+calls are used by programs such as
+.BR bash (1)
+to create process groups in order to implement shell job control.
+.PP
+If the termination of a process causes a process group to become orphaned,
+and if any member of the newly orphaned process group is stopped, then a
+.B SIGHUP
+signal followed by a
+.B SIGCONT
+signal will be sent to each process
+in the newly orphaned process group.
+.\" exit.3 refers to the following text:
+An orphaned process group is one in which the parent of
+every member of process group is either itself also a member
+of the process group or is a member of a process group
+in a different session (see also
+.BR credentials (7)).
+.SH SEE ALSO
.BR getuid (2),
.BR setsid (2),
.BR tcgetpgrp (3),
.BR tcsetpgrp (3),
.BR termios (3),
-.BR ftm (7)
+.BR credentials (7)
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