xref: /netbsd/lib/libc/sys/getpgrp.2 (revision 6550d01e)
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30.\"     @(#)getpgrp.2	8.1 (Berkeley) 6/4/93
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32.Dd August 11, 2002
33.Dt GETPGRP 2
34.Os
35.Sh NAME
36.Nm getpgrp ,
37.Nm getpgid
38.Nd get process group
39.Sh LIBRARY
40.Lb libc
41.Sh SYNOPSIS
42.In unistd.h
43.Ft pid_t
44.Fn getpgrp "void"
45.Ft pid_t
46.Fn getpgid "pid_t pid"
47.Sh DESCRIPTION
48The process group of the current process is returned by
49.Fn getpgrp .
50The process group of the
51.Fa pid
52process is returned by
53.Fn getpgid .
54.Pp
55Process groups are used for distribution of signals, and
56by terminals to arbitrate requests for their input: processes
57that have the same process group as the terminal are foreground
58and may read, while others will block with a signal if they attempt
59to read.
60.Pp
61This call is thus used by programs such as
62.Xr csh 1
63to create
64process groups
65in implementing job control.
66The
67.Fn tcgetpgrp
68and
69.Fn tcsetpgrp
70calls
71are used to get/set the process group of the control terminal.
72.Sh ERRORS
73.Fn getpgrp
74always succeeds, however
75.Fn getpgid
76will succeed unless:
77.Bl -tag -width Er
78.It Bq Er ESRCH
79if there is no process with a process ID equal to
80.Fa pid .
81.El
82.Sh SEE ALSO
83.Xr setpgid 2 ,
84.Xr termios 4
85.Sh STANDARDS
86The
87.Fn getpgrp
88function conforms to
89.St -p1003.1-88 .
90.Sh HISTORY
91The
92.Fn getpgrp
93function call appeared in
94.Bx 4.0 .
95The
96.Fn getpgid
97function call is derived from its usage in
98.At V.4 ,
99and first appeared in
100.Nx 1.3 .
101.Sh COMPATIBILITY
102This version of
103.Fn getpgrp
104differs from past Berkeley versions by not taking a
105.Fa "pid_t pid"
106argument.
107This incompatibility is required by
108.St -p1003.1-90 .
109.Pp
110From the
111.St -p1003.1-90
112Rationale:
113.Lp
114.Bx 4.3
115provides a
116.Fn getpgrp
117function that returns the process group ID for a specified process.
118Although this function is used to support job control, all known
119job-control shells always specify the calling process with this
120function.
121Thus, the simpler System V
122.Fn getpgrp
123suffices, and the added complexity of the
124.Bx 4.3
125.Fn getpgrp
126has been omitted from POSIX.1.
127The old functionality is available from the
128.Fn getpgid
129function.
130