[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 getpgrp
.Nd get process group
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In 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 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
	39	.Nm getpgrp
	40	.Nd get process group
	41	.Sh LIBRARY
	42	.Lb libc
	43	.Sh SYNOPSIS
	44	.In unistd.h
	45	.Ft pid_t
	46	.Fn getpgrp void
	47	.Ft pid_t
	48	.Fn getpgid "pid_t pid"
	49	.Sh DESCRIPTION
	50	The process group of the current process is returned by
	51	.Fn getpgrp .
	52	The process group of the process identified by
	53	.Fa pid
	54	is returned by
	55	.Fn getpgid .
	56	If
	57	.Fa pid
	58	is zero,
	59	.Fn getpgid
	60	returns the process group of the current process.
	61	.Pp
	62	Process groups are used for distribution of signals, and
	63	by terminals to arbitrate requests for their input: processes
	64	that have the same process group as the terminal are foreground
65	and may read, while others will block with a signal if they attempt
66	to read.
67	.Pp
68	This call is thus used by programs such as
69	.Xr csh 1
70	to create
71	process groups
72	in implementing job control.
73	The
74	.Fn tcgetpgrp
75	and
76	.Fn tcsetpgrp
77	calls
78	are used to get/set the process group of the control terminal.
79	.Sh RETURN VALUES
80	The
81	.Fn getpgrp
82	call always succeeds.
83	Upon successful completion, the
84	.Fn getpgid
85	call returns the process group of the specified process;
86	otherwise, it returns a value of \-1 and sets
87	.Va errno
88	to indicate the error.
89	.Sh ERRORS
90	.Fn getpgid
91	will succeed unless:
92	.Bl -tag -width Er
93	.It Bq Er ESRCH
94	there is no process whose process ID equals
95	.Fa pid
96	.El
97	.Sh SEE ALSO
98	.Xr getsid 2 ,
99	.Xr setpgid 2 ,
100	.Xr termios 4
101	.Sh HISTORY
102	The
103	.Fn getpgrp
104	function call appeared in
105	.Bx 4.0 .
106	The
107	.Fn getpgid
108	function call is derived from its usage in System V Release 4.
109	.Sh STANDARDS
110	The
111	.Fn getpgrp
112	function call is expected to conform to
113	.St -p1003.1-90 .
114	.Sh COMPATIBILITY
115	This version of
116	.Fn getpgrp
117	differs from past Berkeley versions by not taking a
118	.Fa "pid_t pid"
119	argument.
120	This incompatibility is required by
121	.St -p1003.1-90 .
122	.Pp
123	From the
124	.St -p1003.1-90
125	Rationale:
126	.Pp
127	.Bx 4.3
128	provides a
129	.Fn getpgrp
130	function that returns the process group ID for a specified process.
131	Although this function is used to support job control, all known
132	job-control shells always specify the calling process with this
133	function.
134	Thus, the simpler
135	.At V
136	.Fn getpgrp
137	suffices, and the added complexity of the
138	.Bx 4.3
139	.Fn getpgrp
140	has been omitted from POSIX.1.
141	The old functionality is available from the
142	.Fn getpgid
143	function.