GETPGRP(2) System Calls Manual GETPGRP(2)
getpgrp, getpgid -- get process group
Standard C Library (libc, -lc)
The process group of the current process is returned by getpgrp(). The
process group of the pid process is returned by getpgid().
Process groups are used for distribution of signals, and by terminals to
arbitrate requests for their input: processes that have the same process
group as the terminal are foreground and may read, while others will
block with a signal if they attempt to read.
This call is thus used by programs such as csh(1) to create process
groups in implementing job control. The tcgetpgrp() and tcsetpgrp()
calls are used to get/set the process group of the control terminal.
getpgrp() always succeeds, however getpgid() will succeed unless:
[ESRCH] if there is no process with a process ID equal to pid.
The getpgrp() function conforms to IEEE Std 1003.1-1988 (``POSIX.1'').
The getpgrp() function call appeared in 4.0BSD. The getpgid() function
call is derived from its usage in AT&T System V Release 4 UNIX, and first
appeared in NetBSD 1.3.
This version of getpgrp() differs from past Berkeley versions by not
taking a pid_t pid argument. This incompatibility is required by IEEE
Std 1003.1-1990 (``POSIX.1'').
From the IEEE Std 1003.1-1990 (``POSIX.1'') Rationale:
4.3BSD provides a getpgrp() function that returns the process group ID
for a specified process. Although this function is used to support job
control, all known job-control shells always specify the calling process
with this function. Thus, the simpler System V getpgrp() suffices, and
the added complexity of the 4.3BSD getpgrp() has been omitted from
POSIX.1. The old functionality is available from the getpgid() function.
NetBSD 6.1.5 August 11, 2002 NetBSD 6.1.5