1SETPGID(2)                 Linux Programmer's Manual                SETPGID(2)
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NAME

6       setpgid, getpgid, setpgrp, getpgrp - set/get process group
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SYNOPSIS

9       #include <unistd.h>
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11       int setpgid(pid_t pid, pid_t pgid);
12       pid_t getpgid(pid_t pid);
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14       pid_t getpgrp(void);                 /* POSIX.1 version */
15       pid_t getpgrp(pid_t pid);            /* BSD version */
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17       int setpgrp(void);                   /* System V version */
18       int setpgrp(pid_t pid, pid_t pgid);  /* BSD version */
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20   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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22       getpgid():
23           _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
24           || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L
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26       setpgrp() (POSIX.1):
27           _SVID_SOURCE || _XOPEN_SOURCE >= 500 ||
28           _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
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30       setpgrp() (BSD), getpgrp() (BSD):
31           _BSD_SOURCE &&
32               ! (_POSIX_SOURCE || _POSIX_C_SOURCE || _XOPEN_SOURCE ||
33                  _XOPEN_SOURCE_EXTENDED || _GNU_SOURCE || _SVID_SOURCE)
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DESCRIPTION

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.
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42       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.
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52       The POSIX.1 version of getpgrp(), which takes no arguments, returns the
53       PGID of the calling process.
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55       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.)
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60       The  System  V-style setpgrp(), which takes no arguments, is equivalent
61       to setpgid(0, 0).
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63       The BSD-specific setpgrp() call, which takes arguments pid and pgid, is
64       equivalent to setpgid(pid, pgid).
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66       The  BSD-specific getpgrp() call, which takes a single pid argument, is
67       equivalent to getpgid(pid).
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RETURN VALUE

70       On success, setpgid() and setpgrp()  return  zero.   On  error,  -1  is
71       returned, and errno is set appropriately.
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73       The POSIX.1 getpgrp() always returns the PGID of the caller.
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75       getpgid(),  and  the  BSD-specific  getpgrp() return a process group on
76       success.  On error, -1 is returned, and errno is set appropriately.
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ERRORS

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‐