NAME
getpgrp, getpgid
— get process group
LIBRARY
library “libc”
SYNOPSIS
#include
<unistd.h>
pid_t
getpgrp(void);
pid_t
getpgid(pid_t
pid);
DESCRIPTION
The process group of the current process is returned bygetpgrp().
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.
COMPATIBILITY
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.
ERRORS
getpgrp() always succeeds, however
getpgid() will succeed unless:
- [
ESRCH] - if there is no process with a process ID equal to pid.
SEE ALSO
STANDARDS
The getpgrp() function conforms to
IEEE Std 1003.1-1988 (“POSIX.1”).
HISTORY
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.