xref: /freebsd/lib/libsys/getpgrp.2 (revision 8269e7673cf033aba67dab8264fe719920c70f87)
1*8269e767SBrooks Davis.\" Copyright (c) 1983, 1991, 1993
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28*8269e767SBrooks Davis.Dd June 4, 1993
29*8269e767SBrooks Davis.Dt GETPGRP 2
30*8269e767SBrooks Davis.Os
31*8269e767SBrooks Davis.Sh NAME
32*8269e767SBrooks Davis.Nm getpgrp
33*8269e767SBrooks Davis.Nd get process group
34*8269e767SBrooks Davis.Sh LIBRARY
35*8269e767SBrooks Davis.Lb libc
36*8269e767SBrooks Davis.Sh SYNOPSIS
37*8269e767SBrooks Davis.In unistd.h
38*8269e767SBrooks Davis.Ft pid_t
39*8269e767SBrooks Davis.Fn getpgrp void
40*8269e767SBrooks Davis.Ft pid_t
41*8269e767SBrooks Davis.Fn getpgid "pid_t pid"
42*8269e767SBrooks Davis.Sh DESCRIPTION
43*8269e767SBrooks DavisThe process group of the current process is returned by
44*8269e767SBrooks Davis.Fn getpgrp .
45*8269e767SBrooks DavisThe process group of the process identified by
46*8269e767SBrooks Davis.Fa pid
47*8269e767SBrooks Davisis returned by
48*8269e767SBrooks Davis.Fn getpgid .
49*8269e767SBrooks DavisIf
50*8269e767SBrooks Davis.Fa pid
51*8269e767SBrooks Davisis zero,
52*8269e767SBrooks Davis.Fn getpgid
53*8269e767SBrooks Davisreturns the process group of the current process.
54*8269e767SBrooks Davis.Pp
55*8269e767SBrooks DavisProcess groups are used for distribution of signals, and
56*8269e767SBrooks Davisby terminals to arbitrate requests for their input: processes
57*8269e767SBrooks Davisthat have the same process group as the terminal are foreground
58*8269e767SBrooks Davisand may read, while others will block with a signal if they attempt
59*8269e767SBrooks Davisto read.
60*8269e767SBrooks Davis.Pp
61*8269e767SBrooks DavisThis system call is thus used by programs such as
62*8269e767SBrooks Davis.Xr csh 1
63*8269e767SBrooks Davisto create
64*8269e767SBrooks Davisprocess groups
65*8269e767SBrooks Davisin implementing job control.
66*8269e767SBrooks DavisThe
67*8269e767SBrooks Davis.Fn tcgetpgrp
68*8269e767SBrooks Davisand
69*8269e767SBrooks Davis.Fn tcsetpgrp
70*8269e767SBrooks Daviscalls
71*8269e767SBrooks Davisare used to get/set the process group of the control terminal.
72*8269e767SBrooks Davis.Sh RETURN VALUES
73*8269e767SBrooks DavisThe
74*8269e767SBrooks Davis.Fn getpgrp
75*8269e767SBrooks Davissystem call always succeeds.
76*8269e767SBrooks DavisUpon successful completion, the
77*8269e767SBrooks Davis.Fn getpgid
78*8269e767SBrooks Davissystem call returns the process group of the specified process;
79*8269e767SBrooks Davisotherwise, it returns a value of \-1 and sets
80*8269e767SBrooks Davis.Va errno
81*8269e767SBrooks Davisto indicate the error.
82*8269e767SBrooks Davis.Sh COMPATIBILITY
83*8269e767SBrooks DavisThis version of
84*8269e767SBrooks Davis.Fn getpgrp
85*8269e767SBrooks Davisdiffers from past Berkeley versions by not taking a
86*8269e767SBrooks Davis.Fa "pid_t pid"
87*8269e767SBrooks Davisargument.
88*8269e767SBrooks DavisThis incompatibility is required by
89*8269e767SBrooks Davis.St -p1003.1-90 .
90*8269e767SBrooks Davis.Pp
91*8269e767SBrooks DavisFrom the
92*8269e767SBrooks Davis.St -p1003.1-90
93*8269e767SBrooks DavisRationale:
94*8269e767SBrooks Davis.Pp
95*8269e767SBrooks Davis.Bx 4.3
96*8269e767SBrooks Davisprovides a
97*8269e767SBrooks Davis.Fn getpgrp
98*8269e767SBrooks Davissystem call that returns the process group ID for a specified process.
99*8269e767SBrooks DavisAlthough this function is used to support job control, all known
100*8269e767SBrooks Davisjob-control shells always specify the calling process with this
101*8269e767SBrooks Davisfunction.
102*8269e767SBrooks DavisThus, the simpler
103*8269e767SBrooks Davis.At V
104*8269e767SBrooks Davis.Fn getpgrp
105*8269e767SBrooks Davissuffices, and the added complexity of the
106*8269e767SBrooks Davis.Bx 4.3
107*8269e767SBrooks Davis.Fn getpgrp
108*8269e767SBrooks Davishas been omitted from POSIX.1.
109*8269e767SBrooks DavisThe old functionality is available from the
110*8269e767SBrooks Davis.Fn getpgid
111*8269e767SBrooks Davissystem call.
112*8269e767SBrooks Davis.Sh ERRORS
113*8269e767SBrooks DavisThe
114*8269e767SBrooks Davis.Fn getpgid
115*8269e767SBrooks Davissystem call
116*8269e767SBrooks Daviswill succeed unless:
117*8269e767SBrooks Davis.Bl -tag -width Er
118*8269e767SBrooks Davis.It Bq Er ESRCH
119*8269e767SBrooks Davisthere is no process whose process ID equals
120*8269e767SBrooks Davis.Fa pid
121*8269e767SBrooks Davis.El
122*8269e767SBrooks Davis.Sh SEE ALSO
123*8269e767SBrooks Davis.Xr getsid 2 ,
124*8269e767SBrooks Davis.Xr setpgid 2 ,
125*8269e767SBrooks Davis.Xr termios 4
126*8269e767SBrooks Davis.Sh STANDARDS
127*8269e767SBrooks DavisThe
128*8269e767SBrooks Davis.Fn getpgrp
129*8269e767SBrooks Davissystem call is expected to conform to
130*8269e767SBrooks Davis.St -p1003.1-90 .
131*8269e767SBrooks Davis.Sh HISTORY
132*8269e767SBrooks DavisThe
133*8269e767SBrooks Davis.Fn getpgrp
134*8269e767SBrooks Davissystem call appeared in
135*8269e767SBrooks Davis.Bx 4.0 .
136*8269e767SBrooks DavisThe
137*8269e767SBrooks Davis.Fn getpgid
138*8269e767SBrooks Davissystem call is derived from its usage in
139*8269e767SBrooks Davis.At V.4 .
140