gno/usr.man/man2/getpgrp.2

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.\"     @(#)getpgrp.2	8.1 (Berkeley) 6/4/93
.\"
.TH GETPGRP 2 "16 January 1997" GNO "System Calls"
.SH NAME
.BR getpgrp
\- get process group
.SH SYNOPSIS
.br
#include <unistd.h>
.sp 1
pid_t
\fB_getpgrp\fR (pid_t \fIpid\fR);
.br
pid_t
\fBgetpgrp\fR (void);
.SH DESCRIPTION
.BR getpgrp
returns the process group of the current process.
.BR _getpgrp
returns the process group of the process specified by
.IR pid .
.LP
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.
.LP
This call is thus used by programs such as
.BR csh (1)
to create
process groups
in implementing job control.
The
.BR tcgetpgrp 
and
.BR tcsetpgrp 
calls
are used to get/set the process group of the control terminal.
.SH RETURNS
On success, the requested process group is returned.  On failure, -1 is
returned and
.BR errno 
is set.
.SH STANDARDS
The
.BR getpgrp 
function conforms to IEEE Std 1003.1-1988 (POSIX).
.SH COMPATIBILITY
This version of
.BR getpgrp 
differs from past GNO (pre-v2.0.6) and Berkeley versions by not taking a
.I "pid_t pid"
argument.
This incompatibility is required by
POSIX 1003.1-88.
.IP "From the POSIX 1003.1-88 Rationale:"
4.3BSD provides a
.BR 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
.BR getpgrp 
suffices, and the added complexity of the 4.3BSD
.BR getpgrp 
has been omitted from POSIX.1.
.LP
The older version of
.BR getpgrp
which takes an argument is available as the non-standard function
.BR _getpgrp .
.SH SEE ALSO
.BR job_control (2),
.BR setpgid (2),
.BR termios (4)
.SH HISTORY
The
.BR getpgrp
function call appeared in 4.0BSD.