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fea681da | 1 | .\" Copyright (c) 1983, 1991 Regents of the University of California. |
0786e308 | 2 | .\" and Copyright (C) 2007, Michael Kerrisk <mtk.manpages@gmail.com> |
fea681da MK |
3 | .\" All rights reserved. |
4 | .\" | |
a9cd9cb7 | 5 | .\" %%%LICENSE_START(BSD_4_CLAUSE_UCB) |
fea681da MK |
6 | .\" Redistribution and use in source and binary forms, with or without |
7 | .\" modification, are permitted provided that the following conditions | |
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10 | .\" notice, this list of conditions and the following disclaimer. | |
11 | .\" 2. Redistributions in binary form must reproduce the above copyright | |
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13 | .\" documentation and/or other materials provided with the distribution. | |
14 | .\" 3. All advertising materials mentioning features or use of this software | |
15 | .\" must display the following acknowledgement: | |
16 | .\" This product includes software developed by the University of | |
17 | .\" California, Berkeley and its contributors. | |
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19 | .\" may be used to endorse or promote products derived from this software | |
20 | .\" without specific prior written permission. | |
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22 | .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND | |
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8c9302dc | 33 | .\" %%%LICENSE_END |
fea681da MK |
34 | .\" |
35 | .\" @(#)getpgrp.2 6.4 (Berkeley) 3/10/91 | |
36 | .\" | |
37 | .\" Modified 1993-07-24 by Rik Faith <faith@cs.unc.edu> | |
38 | .\" Modified 1995-04-15 by Michael Chastain <mec@shell.portal.com>: | |
39 | .\" Added 'getpgid'. | |
40 | .\" Modified 1996-07-21 by Andries Brouwer <aeb@cwi.nl> | |
41 | .\" Modified 1996-11-06 by Eric S. Raymond <esr@thyrsus.com> | |
42 | .\" Modified 1999-09-02 by Michael Haardt <michael@moria.de> | |
c11b1abf | 43 | .\" Modified 2002-01-18 by Michael Kerrisk <mtk.manpages@gmail.com> |
fea681da | 44 | .\" Modified 2003-01-20 by Andries Brouwer <aeb@cwi.nl> |
0bbb92a3 MK |
45 | .\" 2007-07-25, mtk, fairly substantial rewrites and rearrangements |
46 | .\" of text. | |
fea681da | 47 | .\" |
b8efb414 | 48 | .TH SETPGID 2 2016-10-08 "Linux" "Linux Programmer's Manual" |
fea681da MK |
49 | .SH NAME |
50 | setpgid, getpgid, setpgrp, getpgrp \- set/get process group | |
51 | .SH SYNOPSIS | |
52 | .B #include <unistd.h> | |
53 | .sp | |
54 | .BI "int setpgid(pid_t " pid ", pid_t " pgid ); | |
55 | .br | |
56 | .BI "pid_t getpgid(pid_t " pid ); | |
0bbb92a3 | 57 | .sp |
72ef5c5c | 58 | .BR "pid_t getpgrp(void);" " /* POSIX.1 version */" |
fea681da | 59 | .br |
72ef5c5c | 60 | .BI "pid_t getpgrp(pid_t " pid ");\ \ \ \ \ \ \ \ \ \ \ " |
0bbb92a3 MK |
61 | /* BSD version */ |
62 | .sp | |
72ef5c5c | 63 | .BR "int setpgrp(void);" " /* System V version */" |
fea681da | 64 | .br |
72ef5c5c | 65 | .BI "int setpgrp(pid_t " pid ", pid_t " pgid ");\ " |
0bbb92a3 MK |
66 | /* BSD version */ |
67 | .sp | |
68 | .in -4n | |
69 | Feature Test Macro Requirements for glibc (see | |
70 | .BR feature_test_macros (7)): | |
71 | .in | |
72 | .sp | |
cc4615cc | 73 | .ad l |
fc541b7a | 74 | .PD 0 |
0bbb92a3 | 75 | .BR getpgid (): |
fc541b7a | 76 | .RS 4 |
cf7fa0a1 MK |
77 | _XOPEN_SOURCE\ >=\ 500 |
78 | .\" || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED | |
3ba63d80 | 79 | .br |
cf7fa0a1 | 80 | || /* Since glibc 2.12: */ _POSIX_C_SOURCE\ >=\ 200809L |
fc541b7a MK |
81 | .RE |
82 | .sp | |
83 | .BR setpgrp "() (POSIX.1):" | |
84 | .nf | |
f8619b6a | 85 | _XOPEN_SOURCE\ >=\ 500 |
cf7fa0a1 | 86 | .\" || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED |
f8619b6a MK |
87 | || /* Since glibc 2.19: */ _DEFAULT_SOURCE |
88 | || /* Glibc versions <= 2.19: */ _SVID_SOURCE | |
fc541b7a | 89 | .fi |
0bbb92a3 MK |
90 | .sp |
91 | .BR setpgrp "()\ (BSD)," | |
f8619b6a | 92 | .BR getpgrp "()\ (BSD):" |
fc541b7a | 93 | .nf |
f8619b6a | 94 | [These are available only before glibc 2.19] |
fc541b7a MK |
95 | _BSD_SOURCE && |
96 | !\ (_POSIX_SOURCE || _POSIX_C_SOURCE || _XOPEN_SOURCE || | |
52d1e2b2 | 97 | _GNU_SOURCE || _SVID_SOURCE) |
fc541b7a MK |
98 | .fi |
99 | .PD | |
02e92562 | 100 | .ad |
fea681da | 101 | .SH DESCRIPTION |
0bbb92a3 MK |
102 | All of these interfaces are available on Linux, |
103 | and are used for getting and setting the | |
104 | process group ID (PGID) of a process. | |
105 | The preferred, POSIX.1-specified ways of doing this are: | |
106 | .BR getpgrp (void), | |
107 | for retrieving the calling process's PGID; and | |
108 | .BR setpgid (), | |
109 | for setting a process's PGID. | |
110 | ||
e511ffb6 | 111 | .BR setpgid () |
0bbb92a3 | 112 | sets the PGID of the process specified by |
fea681da MK |
113 | .I pid |
114 | to | |
115 | .IR pgid . | |
116 | If | |
117 | .I pid | |
17c69289 | 118 | is zero, then the process ID of the calling process is used. |
c13182ef | 119 | If |
fea681da | 120 | .I pgid |
17c69289 | 121 | is zero, then the PGID of the process specified by |
fea681da | 122 | .I pid |
17c69289 | 123 | is made the same as its process ID. |
60a90ecd MK |
124 | If |
125 | .BR setpgid () | |
126 | is used to move a process from one process | |
fea681da | 127 | group to another (as is done by some shells when creating pipelines), |
0bbb92a3 MK |
128 | both process groups must be part of the same session (see |
129 | .BR setsid (2) | |
e0bf9127 | 130 | and |
0bbb92a3 | 131 | .BR credentials (7)). |
c13182ef | 132 | In this case, |
fea681da MK |
133 | the \fIpgid\fP specifies an existing process group to be joined and the |
134 | session ID of that group must match the session ID of the joining process. | |
135 | ||
0bbb92a3 MK |
136 | The POSIX.1 version of |
137 | .BR getpgrp (), | |
138 | which takes no arguments, | |
139 | returns the PGID of the calling process. | |
140 | ||
e511ffb6 | 141 | .BR getpgid () |
0bbb92a3 | 142 | returns the PGID of the process specified by |
fea681da MK |
143 | .IR pid . |
144 | If | |
145 | .I pid | |
a1ffe9f5 | 146 | is zero, the process ID of the calling process is used. |
0bbb92a3 MK |
147 | (Retrieving the PGID of a process other than the caller is rarely |
148 | necessary, and the POSIX.1 | |
149 | .BR getpgrp () | |
150 | is preferred for that task.) | |
fea681da | 151 | |
efbfd7ec | 152 | The System\ V-style |
aadd7709 MK |
153 | .BR setpgrp (), |
154 | which takes no arguments, is equivalent to | |
ab7b478b | 155 | .IR "setpgid(0,\ 0)" . |
fea681da | 156 | |
0bbb92a3 MK |
157 | The BSD-specific |
158 | .BR setpgrp () | |
159 | call, which takes arguments | |
160 | .I pid | |
fea681da | 161 | and |
0bbb92a3 | 162 | .IR pgid , |
8e6ee8f3 | 163 | is a wrapper function that calls |
ded44f9b MK |
164 | |
165 | setpgid(pid, pgid) | |
166 | ||
0bbb92a3 MK |
167 | .\" The true BSD setpgrp() system call differs in allowing the PGID |
168 | .\" to be set to arbitrary values, rather than being restricted to | |
169 | .\" PGIDs in the same session. | |
ded44f9b MK |
170 | Since glibc 2.19, the BSD-specific |
171 | .BR setpgrp () | |
172 | function is no longer exposed by | |
173 | .IR <unistd.h> ; | |
174 | calls should be replaced with the | |
175 | .BR setpgid () | |
176 | call shown above. | |
fea681da | 177 | |
0bbb92a3 MK |
178 | The BSD-specific |
179 | .BR getpgrp () | |
180 | call, which takes a single | |
181 | .I pid | |
ded44f9b MK |
182 | argument, is a wrapper function that calls |
183 | ||
184 | getpgid(pid) | |
185 | ||
186 | Since glibc 2.19, the BSD-specific | |
187 | .BR getpgrp () | |
188 | function is no longer exposed by | |
189 | .IR <unistd.h> ; | |
190 | calls should be replaced with calls to the POSIX.1 | |
191 | .BR getpgrp () | |
192 | which takes no arguments (if the intent is to obtain the caller's PGID), | |
193 | or with the | |
194 | .BR getpgid () | |
195 | call shown above. | |
47297adb | 196 | .SH RETURN VALUE |
fea681da | 197 | On success, |
ae050d9a | 198 | .BR setpgid () |
c13182ef | 199 | and |
ae050d9a | 200 | .BR setpgrp () |
c13182ef MK |
201 | return zero. |
202 | On error, \-1 is returned, and | |
fea681da MK |
203 | .I errno |
204 | is set appropriately. | |
205 | ||
0bbb92a3 MK |
206 | The POSIX.1 |
207 | .BR getpgrp () | |
aadd7709 | 208 | always returns the PGID of the caller. |
0bbb92a3 MK |
209 | |
210 | .BR getpgid (), | |
211 | and the BSD-specific | |
212 | .BR getpgrp () | |
213 | return a process group on success. | |
fea681da MK |
214 | On error, \-1 is returned, and |
215 | .I errno | |
216 | is set appropriately. | |
fea681da MK |
217 | .SH ERRORS |
218 | .TP | |
219 | .B EACCES | |
220 | An attempt was made to change the process group ID | |
221 | of one of the children of the calling process and the child had | |
60a90ecd MK |
222 | already performed an |
223 | .BR execve (2) | |
224 | .RB ( setpgid (), | |
225 | .BR setpgrp ()). | |
fea681da MK |
226 | .TP |
227 | .B EINVAL | |
228 | .I pgid | |
229 | is less than 0 | |
60a90ecd MK |
230 | .RB ( setpgid (), |
231 | .BR setpgrp ()). | |
fea681da MK |
232 | .TP |
233 | .B EPERM | |
c13182ef MK |
234 | An attempt was made to move a process into a process group in a |
235 | different session, or to change the process | |
236 | group ID of one of the children of the calling process and the | |
fea681da MK |
237 | child was in a different session, or to change the process group ID of |
238 | a session leader | |
60a90ecd MK |
239 | .RB ( setpgid (), |
240 | .BR setpgrp ()). | |
fea681da MK |
241 | .TP |
242 | .B ESRCH | |
243 | For | |
e511ffb6 | 244 | .BR getpgid (): |
fea681da MK |
245 | .I pid |
246 | does not match any process. | |
247 | For | |
e511ffb6 | 248 | .BR setpgid (): |
fea681da | 249 | .I pid |
a1ffe9f5 | 250 | is not the calling process and not a child of the calling process. |
47297adb | 251 | .SH CONFORMING TO |
e511ffb6 | 252 | .BR setpgid () |
0bbb92a3 | 253 | and the version of |
e511ffb6 | 254 | .BR getpgrp () |
d68b2713 | 255 | with no arguments |
97c1eac8 | 256 | conform to POSIX.1-2001. |
0bbb92a3 MK |
257 | |
258 | POSIX.1-2001 also specifies | |
e511ffb6 | 259 | .BR getpgid () |
0bbb92a3 MK |
260 | and the version of |
261 | .BR setpgrp () | |
262 | that takes no arguments. | |
55cfc574 MK |
263 | (POSIX.1-2008 marks this |
264 | .BR setpgrp () | |
265 | specification as obsolete.) | |
0bbb92a3 MK |
266 | |
267 | The version of | |
268 | .BR getpgrp () | |
269 | with one argument and the version of | |
270 | .BR setpgrp () | |
271 | that takes two arguments derive from 4.2BSD, | |
272 | and are not specified by POSIX.1. | |
fea681da | 273 | .SH NOTES |
c13182ef | 274 | A child created via |
73ac0666 MK |
275 | .BR fork (2) |
276 | inherits its parent's process group ID. | |
aadd7709 | 277 | The PGID is preserved across an |
73ac0666 MK |
278 | .BR execve (2). |
279 | ||
0bbb92a3 MK |
280 | Each process group is a member of a session and each process is a |
281 | member of the session of which its process group is a member. | |
1a765504 MK |
282 | (See |
283 | .BR credentials (7).) | |
0bbb92a3 MK |
284 | |
285 | A session can have a controlling terminal. | |
286 | At any time, one (and only one) of the process groups | |
287 | in the session can be the foreground process group | |
288 | for the terminal; | |
289 | the remaining process groups are in the background. | |
290 | If a signal is generated from the terminal (e.g., typing the | |
291 | interrupt key to generate | |
292 | .BR SIGINT ), | |
293 | that signal is sent to the foreground process group. | |
294 | (See | |
295 | .BR termios (3) | |
296 | for a description of the characters that generate signals.) | |
aadd7709 MK |
297 | Only the foreground process group may |
298 | .BR read (2) | |
299 | from the terminal; | |
300 | if a background process group tries to | |
301 | .BR read (2) | |
15b17877 | 302 | from the terminal, then the group is sent a |
07bfe93f | 303 | .B SIGTTIN |
0bbb92a3 MK |
304 | signal, which suspends it. |
305 | The | |
306 | .BR tcgetpgrp (3) | |
307 | and | |
308 | .BR tcsetpgrp (3) | |
309 | functions are used to get/set the foreground | |
310 | process group of the controlling terminal. | |
311 | ||
312 | The | |
e511ffb6 | 313 | .BR setpgid () |
c3dfd2c8 | 314 | and |
0bbb92a3 MK |
315 | .BR getpgrp () |
316 | calls are used by programs such as | |
317 | .BR bash (1) | |
318 | to create process groups in order to implement shell job control. | |
319 | ||
343313da | 320 | If the termination of a process causes a process group to become orphaned, |
0bbb92a3 MK |
321 | and if any member of the newly orphaned process group is stopped, then a |
322 | .B SIGHUP | |
323 | signal followed by a | |
324 | .B SIGCONT | |
325 | signal will be sent to each process | |
326 | in the newly orphaned process group. | |
a38dc43a MK |
327 | .\" exit.3 refers to the following text: |
328 | An orphaned process group is one in which the parent of | |
329 | every member of process group is either itself also a member | |
330 | of the process group or is a member of a process group | |
331 | in a different session (see also | |
332 | .BR credentials (7)). | |
47297adb | 333 | .SH SEE ALSO |
fea681da MK |
334 | .BR getuid (2), |
335 | .BR setsid (2), | |
336 | .BR tcgetpgrp (3), | |
337 | .BR tcsetpgrp (3), | |
0786e308 MK |
338 | .BR termios (3), |
339 | .BR credentials (7) |