[apple/xnu.git] / bsd / man / man2 / getpgrp.2

.\" Copyright (c) 1983, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)getpgrp.2	8.1 (Berkeley) 6/4/93
.\" $FreeBSD: src/lib/libc/sys/getpgrp.2,v 1.11.2.6 2001/12/14 18:34:00 ru Exp $
.\"
.Dd June 4, 1993
.Dt GETPGRP 2
.Os
.Sh NAME
.Nm getpgid ,
.Nm getpgrp
.Nd get process group
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In unistd.h
.Ft pid_t
.Fo getpgid
.Fa "pid_t pid"
.Fc
.Ft pid_t
.Fo getpgrp
.Fa void
.Fc
.Sh DESCRIPTION
The process group of the current process is returned by
.Fn getpgrp .
The process group of the process identified by
.Fa pid
is returned by
.Fn getpgid .
If
.Fa pid
is zero,
.Fn getpgid
returns the process group of the current process.
.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 RETURN VALUES
The
.Fn getpgrp
call always succeeds.
Upon successful completion, the
.Fn getpgid
call returns the process group of the specified process;
otherwise, it returns a value of \-1 and sets
.Va errno
to indicate the error.
.Sh ERRORS
.Fn getpgid
will succeed unless:
.Bl -tag -width Er
.\" ==========
.It Bq Er ESRCH
There is no process whose process ID equals
.Fa pid .
.El
.Sh SEE ALSO
.Xr getsid 2 ,
.Xr setpgid 2 ,
.Xr termios 4
.Sh HISTORY
The
.Fn getpgrp
function call appeared in
.Bx 4.0 .
The
.Fn getpgid
function call is derived from its usage in System V Release 4.
.Sh STANDARDS
The
.Fn getpgrp
function call is expected to conform to
.St -p1003.1-90 .
.Sh COMPATIBILITY
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 -p1003.1-90 .
.Pp
From the
.St -p1003.1-90
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
.At V
.Fn getpgrp
suffices, and the added complexity of the
.Bx 4.3
.Fn getpgrp
has been omitted from POSIX.1.
The old functionality is available from the
.Fn getpgid
function.
Commit	Line	Data
9bccf70c A	1	.\" Copyright (c) 1983, 1991, 1993
	2	.\" The Regents of the University of California. All rights reserved.
	3	.\"
	4	.\" Redistribution and use in source and binary forms, with or without
	5	.\" modification, are permitted provided that the following conditions
	6	.\" are met:
	7	.\" 1. Redistributions of source code must retain the above copyright
	8	.\" notice, this list of conditions and the following disclaimer.
	9	.\" 2. Redistributions in binary form must reproduce the above copyright
	10	.\" notice, this list of conditions and the following disclaimer in the
	11	.\" documentation and/or other materials provided with the distribution.
	12	.\" 3. All advertising materials mentioning features or use of this software
	13	.\" must display the following acknowledgement:
	14	.\" This product includes software developed by the University of
	15	.\" California, Berkeley and its contributors.
	16	.\" 4. Neither the name of the University nor the names of its contributors
	17	.\" may be used to endorse or promote products derived from this software
	18	.\" without specific prior written permission.
	19	.\"
	20	.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	21	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	22	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	23	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	24	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	25	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	26	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	27	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	28	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	29	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	30	.\" SUCH DAMAGE.
	31	.\"
	32	.\" @(#)getpgrp.2 8.1 (Berkeley) 6/4/93
	33	.\" $FreeBSD: src/lib/libc/sys/getpgrp.2,v 1.11.2.6 2001/12/14 18:34:00 ru Exp $
	34	.\"
	35	.Dd June 4, 1993
	36	.Dt GETPGRP 2
	37	.Os
	38	.Sh NAME
2d21ac55	39	.Nm getpgid ,
9bccf70c A	40	.Nm getpgrp
	41	.Nd get process group
	42	.Sh LIBRARY
	43	.Lb libc
	44	.Sh SYNOPSIS
	45	.In unistd.h
	46	.Ft pid_t
2d21ac55 A	47	.Fo getpgid
	48	.Fa "pid_t pid"
	49	.Fc
9bccf70c	50	.Ft pid_t
2d21ac55 A	51	.Fo getpgrp
	52	.Fa void
	53	.Fc
9bccf70c A	54	.Sh DESCRIPTION
	55	The process group of the current process is returned by
	56	.Fn getpgrp .
	57	The process group of the process identified by
	58	.Fa pid
	59	is returned by
	60	.Fn getpgid .
	61	If
	62	.Fa pid
	63	is zero,
	64	.Fn getpgid
	65	returns the process group of the current process.
	66	.Pp
	67	Process groups are used for distribution of signals, and
	68	by terminals to arbitrate requests for their input: processes
	69	that have the same process group as the terminal are foreground
	70	and may read, while others will block with a signal if they attempt
	71	to read.
	72	.Pp
	73	This call is thus used by programs such as
	74	.Xr csh 1
	75	to create
	76	process groups
	77	in implementing job control.
	78	The
	79	.Fn tcgetpgrp
	80	and
	81	.Fn tcsetpgrp
	82	calls
	83	are used to get/set the process group of the control terminal.
	84	.Sh RETURN VALUES
	85	The
	86	.Fn getpgrp
	87	call always succeeds.
	88	Upon successful completion, the
	89	.Fn getpgid
	90	call returns the process group of the specified process;
	91	otherwise, it returns a value of \-1 and sets
	92	.Va errno
	93	to indicate the error.
	94	.Sh ERRORS
	95	.Fn getpgid
	96	will succeed unless:
	97	.Bl -tag -width Er
2d21ac55	98	.\" ==========
9bccf70c	99	.It Bq Er ESRCH
2d21ac55 A	100	There is no process whose process ID equals
2d21ac55 A	101	.Fa pid .
9bccf70c A	102	.El
	103	.Sh SEE ALSO
	104	.Xr getsid 2 ,
	105	.Xr setpgid 2 ,
	106	.Xr termios 4
	107	.Sh HISTORY
	108	The
	109	.Fn getpgrp
	110	function call appeared in
	111	.Bx 4.0 .
	112	The
	113	.Fn getpgid
	114	function call is derived from its usage in System V Release 4.
	115	.Sh STANDARDS
	116	The
	117	.Fn getpgrp
	118	function call is expected to conform to
	119	.St -p1003.1-90 .
	120	.Sh COMPATIBILITY
	121	This version of
	122	.Fn getpgrp
	123	differs from past Berkeley versions by not taking a
	124	.Fa "pid_t pid"
	125	argument.
	126	This incompatibility is required by
	127	.St -p1003.1-90 .
	128	.Pp
	129	From the
	130	.St -p1003.1-90
	131	Rationale:
	132	.Pp
	133	.Bx 4.3
	134	provides a
	135	.Fn getpgrp
	136	function that returns the process group ID for a specified process.
	137	Although this function is used to support job control, all known
	138	job-control shells always specify the calling process with this
	139	function.
	140	Thus, the simpler
	141	.At V
	142	.Fn getpgrp
	143	suffices, and the added complexity of the
	144	.Bx 4.3
	145	.Fn getpgrp
	146	has been omitted from POSIX.1.
	147	The old functionality is available from the
	148	.Fn getpgid
	149	function.