GETPGRP(2) BSD System Calls Manual GETPGRP(2)
getpgrp -- get process group
Standard C Library (libc, -lc)
The process group of the current process is returned by getpgrp(). The
process group of the process identified by pid is returned by getpgid().
If pid is zero, getpgid() returns the process group of the current
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.
The getpgrp() call always succeeds. Upon successful completion, the
getpgid() call returns the process group of the specified process; other-
wise, it returns a value of -1 and sets errno to indicate the error.
getpgid() will succeed unless:
[ESRCH] there is no process whose process ID equals pid
getsid(2), setpgid(2), termios(4)
The getpgrp() function call appeared in 4.0BSD. The getpgid() function
call is derived from its usage in System V Release 4.
The getpgrp() function call is expected to conform to ISO/IEC 9945-1:1990
This version of getpgrp() differs from past Berkeley versions by not tak-
ing a pid_t pid argument. This incompatibility is required by ISO/IEC
From the ISO/IEC 9945-1:1990 (``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 AT&T System V UNIX getpgrp() suf-
fices, and the added complexity of the 4.3BSD getpgrp() has been omitted
from POSIX.1. The old functionality is available from the getpgid()
BSD June 4, 1993 BSD