1SETPGID(2) Linux Programmer's Manual SETPGID(2)
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6 setpgid, getpgid, setpgrp, getpgrp - set/get process group
7
9 #include <unistd.h>
10 int setpgid(pid_t pid, pid_t pgid);
12 pid_t getpgid(pid_t pid);
13 pid_t getpgrp(void); /* POSIX.1 version */
15 pid_t getpgrp(pid_t pid); /* BSD version */
16 int setpgrp(void); /* System V version */
18 int setpgrp(pid_t pid, pid_t pgid); /* BSD version */
19 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
21 getpgid():
23 _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
24 || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L
25 setpgrp() (POSIX.1):
27 _SVID_SOURCE || _XOPEN_SOURCE >= 500 ||
28 _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
29 setpgrp() (BSD), getpgrp() (BSD):
31 _BSD_SOURCE &&
32 ! (_POSIX_SOURCE || _POSIX_C_SOURCE || _XOPEN_SOURCE ||
33 _XOPEN_SOURCE_EXTENDED || _GNU_SOURCE || _SVID_SOURCE)
34
36 All of these interfaces are available on Linux, and are used for get‐
37 ting and setting the process group ID (PGID) of a process. The pre‐
38 ferred, POSIX.1-specified ways of doing this are: getpgrp(void), for
39 retrieving the calling process's PGID; and setpgid(), for setting a
40 process's PGID.
41 setpgid() sets the PGID of the process specified by pid to pgid. If
43 pid is zero, then the process ID of the calling process is used. If
44 pgid is zero, then the PGID of the process specified by pid is made the
45 same as its process ID. If setpgid() is used to move a process from
46 one process group to another (as is done by some shells when creating
47 pipelines), both process groups must be part of the same session (see
48 setsid(2) and credentials(7)). In this case, the pgid specifies an
49 existing process group to be joined and the session ID of that group
50 must match the session ID of the joining process.
51 The POSIX.1 version of getpgrp(), which takes no arguments, returns the
53 PGID of the calling process.
54 getpgid() returns the PGID of the process specified by pid. If pid is
56 zero, the process ID of the calling process is used. (Retrieving the
57 PGID of a process other than the caller is rarely necessary, and the
58 POSIX.1 getpgrp() is preferred for that task.)
59 The System V-style setpgrp(), which takes no arguments, is equivalent
61 to setpgid(0, 0).
62 The BSD-specific setpgrp() call, which takes arguments pid and pgid, is
64 equivalent to setpgid(pid, pgid).
65 The BSD-specific getpgrp() call, which takes a single pid argument, is
67 equivalent to getpgid(pid).
68
70 On success, setpgid() and setpgrp() return zero. On error, -1 is
71 returned, and errno is set appropriately.
72 The POSIX.1 getpgrp() always returns the PGID of the caller.
74 getpgid(), and the BSD-specific getpgrp() return a process group on
76 success. On error, -1 is returned, and errno is set appropriately.
77
79 EACCES An attempt was made to change the process group ID of one of the
80 children of the calling process and the child had already per‐
81 formed an execve(2) (setpgid(), setpgrp()).
82 EINVAL pgid is less than 0 (setpgid(), setpgrp()).
84 EPERM An attempt was made to move a process into a process group in a
86 different session, or to change the process group ID of one of
87 the children of the calling process and the child was in a dif‐
88 ferent session, or to change the process group ID of a session
89 leader (setpgid(), setpgrp()).
90 ESRCH For getpgid(): pid does not match any process. For setpgid():
92 pid is not the calling process and not a child of the calling
93 process.
94
96 setpgid() and the version of getpgrp() with no arguments conform to
97 POSIX.1-2001.
98 POSIX.1-2001 also specifies getpgid() and the version of setpgrp() that
100 takes no arguments. (POSIX.1-2008 marks this setpgrp() specification
101 as obsolete.)
102 The version of getpgrp() with one argument and the version of setpgrp()
104 that takes two arguments derive from 4.2BSD, and are not specified by
105 POSIX.1.
106
108 A child created via fork(2) inherits its parent's process group ID.
109 The PGID is preserved across an execve(2).
110 Each process group is a member of a session and each process is a mem‐
112 ber of the session of which its process group is a member.
113 A session can have a controlling terminal. At any time, one (and only
115 one) of the process groups in the session can be the foreground process
116 group for the terminal; the remaining process groups are in the back‐
117 ground. If a signal is generated from the terminal (e.g., typing the
118 interrupt key to generate SIGINT), that signal is sent to the fore‐
119 ground process group. (See termios(3) for a description of the charac‐
120 ters that generate signals.) Only the foreground process group may
121 read(2) from the terminal; if a background process group tries to
122 read(2) from the terminal, then the group is sent a SIGTTIN signal,
123 which suspends it. The tcgetpgrp(3) and tcsetpgrp(3) functions are
124 used to get/set the foreground process group of the controlling termi‐
125 nal.
126 The setpgid() and getpgrp() calls are used by programs such as bash(1)
128 to create process groups in order to implement shell job control.
129 If a session has a controlling terminal, and the CLOCAL flag for that
131 terminal is not set, and a terminal hangup occurs, then the session
132 leader is sent a SIGHUP. If the session leader exits, then a SIGHUP
133 signal will also be sent to each process in the foreground process
134 group of the controlling terminal.
135 If the exit of the process causes a process group to become orphaned,
137 and if any member of the newly orphaned process group is stopped, then
138 a SIGHUP signal followed by a SIGCONT signal will be sent to each
139 process in the newly orphaned process group. An orphaned process group
140 is one in which the parent of every member of process group is either
141 itself also a member of the process group or is a member of a process
142 group in a different session (see also credentials(7)).
143
145 getuid(2), setsid(2), tcgetpgrp(3), tcsetpgrp(3), termios(3), creden‐
146 tials(7)
147
149 This page is part of release 3.53 of the Linux man-pages project. A
150 description of the project, and information about reporting bugs, can
151 be found at http://www.kernel.org/doc/man-pages/.
152Linux 2013-07-31 SETPGID(2)