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31.\"     @(#)getpgrp.2	8.1 (Berkeley) 6/4/93
32.\"
33.Dd $Mdocdate: October 13 2022 $
34.Dt GETPGRP 2
35.Os
36.Sh NAME
37.Nm getpgrp ,
38.Nm getpgid
39.Nd get process group
40.Sh SYNOPSIS
41.In unistd.h
42.Ft pid_t
43.Fn getpgrp "void"
44.Ft pid_t
45.Fn getpgid "pid_t pid"
46.Sh DESCRIPTION
47The process group of the current process is returned by
48.Fn getpgrp .
49The process group of the
50.Fa pid
51process is returned by
52.Fn getpgid .
53If
54.Fa pid
55is zero,
56.Fn getpgid
57returns the process group of the current process.
58.Pp
59Process groups are used for distribution of signals, and
60by terminals to arbitrate requests for their input: processes
61that have the same process group as the terminal are foreground
62and may read, while others will block with a signal if they attempt
63to read.
64.Pp
65These calls are thus used by programs such as
66.Xr csh 1
67to create
68process groups
69in implementing job control.
70The
71.Fn tcgetpgrp
72and
73.Fn tcsetpgrp
74calls are used to get/set the process group of the controlling terminal.
75.Sh ERRORS
76.Fn getpgrp
77always succeeds, however
78.Fn getpgid
79will succeed unless:
80.Bl -tag -width Er
81.It Bq Er EPERM
82The current process and the process
83.Fa pid
84are not in the same session.
85.It Bq Er ESRCH
86There is no process with a process ID equal to
87.Fa pid .
88.El
89.Sh SEE ALSO
90.Xr setpgid 2 ,
91.Xr termios 4
92.Sh STANDARDS
93The
94.Fn getpgrp
95and
96.Fn getpgid
97functions conform to
98.St -p1003.1-2008 .
99.Sh HISTORY
100A
101.Fn getpgrp
102function call that took a
103.Fa "pid_t pid"
104argument appeared in
105.Bx 4.0 .
106This version, without an argument, is derived from its usage in
107System V Release 4, and first appeared in
108.Nx 0.9 .
109.Pp
110The
111.Fn getpgid
112function call is derived from its usage in System V Release 4, and
113first appeared in
114.Nx 1.2a .
115