xref: /dragonfly/lib/libc/sys/getpgrp.2 (revision 7bc7e232)
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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.\" $DragonFly: src/lib/libc/sys/getpgrp.2,v 1.4 2007/02/25 18:35:05 swildner Exp $
35.\"
36.Dd June 4, 1993
37.Dt GETPGRP 2
38.Os
39.Sh NAME
40.Nm getpgrp ,
41.Nm getpgid
42.Nd get process group
43.Sh LIBRARY
44.Lb libc
45.Sh SYNOPSIS
46.In unistd.h
47.Ft pid_t
48.Fn getpgrp void
49.Ft pid_t
50.Fn getpgid "pid_t pid"
51.Sh DESCRIPTION
52The process group of the current process is returned by
53.Fn getpgrp .
54The process group of the process identified by
55.Fa pid
56is returned by
57.Fn getpgid .
58If
59.Fa pid
60is zero,
61.Fn getpgid
62returns the process group of the current process.
63.Pp
64Process groups are used for distribution of signals, and
65by terminals to arbitrate requests for their input: processes
66that have the same process group as the terminal are foreground
67and may read, while others will block with a signal if they attempt
68to read.
69.Pp
70This call is thus used by programs such as
71.Xr csh 1
72to create
73process groups
74in implementing job control.
75The
76.Fn tcgetpgrp
77and
78.Fn tcsetpgrp
79calls
80are used to get/set the process group of the control terminal.
81.Sh RETURN VALUES
82The
83.Fn getpgrp
84call always succeeds.
85Upon successful completion, the
86.Fn getpgid
87call returns the process group of the specified process;
88otherwise, it returns a value of \-1 and sets
89.Va errno
90to indicate the error.
91.Sh COMPATIBILITY
92This version of
93.Fn getpgrp
94differs from past Berkeley versions by not taking a
95.Fa "pid_t pid"
96argument.
97This incompatibility is required by
98.St -p1003.1-90 .
99.Pp
100From the
101.St -p1003.1-90
102Rationale:
103.Pp
104.Bx 4.3
105provides a
106.Fn getpgrp
107function that returns the process group ID for a specified process.
108Although this function is used to support job control, all known
109job-control shells always specify the calling process with this
110function.
111Thus, the simpler
112.At V
113.Fn getpgrp
114suffices, and the added complexity of the
115.Bx 4.3
116.Fn getpgrp
117has been omitted from POSIX.1.
118The old functionality is available from the
119.Fn getpgid
120function.
121.Sh ERRORS
122.Fn getpgid
123will succeed unless:
124.Bl -tag -width Er
125.It Bq Er ESRCH
126there is no process whose process ID equals
127.Fa pid
128.El
129.Sh SEE ALSO
130.Xr getsid 2 ,
131.Xr setpgid 2 ,
132.Xr termios 4
133.Sh STANDARDS
134The
135.Fn getpgrp
136function call is expected to conform to
137.St -p1003.1-90 .
138.Sh HISTORY
139The
140.Fn getpgrp
141function call appeared in
142.Bx 4.0 .
143The
144.Fn getpgid
145function call is derived from its usage in System V Release 4.
146