.\"	$OpenBSD: getpgrp.2,v 1.12 2003/06/02 20:18:39 millert Exp $
.\"	$NetBSD: getpgrp.2,v 1.8 1995/02/27 12:33:09 cgd Exp $
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.\"     @(#)getpgrp.2	8.1 (Berkeley) 6/4/93
.\"
.Dd June 4, 1993
.Dt GETPGRP 2
.Os
.Sh NAME
.Nm getpgrp
.Nd get process group
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft pid_t
.Fn getpgrp "void"
.Ft pid_t
.Fn getpgid "pid_t pid"
.Sh DESCRIPTION
The process group of the current process is returned by
.Fn getpgrp .
The process group of the
.Fa pid
process is returned by
.Fn getpgid .
.Pp
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.
.Pp
This call is thus used by programs such as
.Xr csh 1
to create
process groups
in implementing job control.
The
.Fn tcgetpgrp
and
.Fn tcsetpgrp
calls
are used to get/set the process group of the control terminal.
.Sh ERRORS
.Fn getpgrp
always succeeds, however
.Fn getpgid
will succeed unless:
.Bl -tag -width Er
.It Bq Er EPERM
The current process and the process
.Fa pid
are not in the same session.
.It Bq Er ESRCH
There is no process with a process ID equal to
.Fa pid .
.El
.Sh SEE ALSO
.Xr setpgid 2 ,
.Xr termios 4
.Sh STANDARDS
This version of
.Fn getpgrp
differs from past Berkeley versions by not taking a
.Fa "pid_t pid"
argument.
This incompatibility is required by
.St -p1003.1-88 .
.Pp
From the
.St -p1003.1-88
Rationale:
.Pp
.Bx 4.3
provides a
.Fn getpgrp
function that returns the process group ID for a specified process.
Although this function is used to support job control, all known
job-control shells always specify the calling process with this
function.
Thus, the simpler System V
.Fn getpgrp
suffices, and the added complexity of the
.Bx 4.3
.Fn getpgrp
has been omitted from POSIX.1.
.Pp
The
.Fn getpgrp
function conforms to
.St -p1003.1-88 .
The
.Fn getpgid
function call is derived from its usage in System V Release 4, and
first appeared in
.Nx 1.2a .
.Sh HISTORY
The
.Fn getpgrp
function call appeared in
.Bx 4.0 .