NAME
getpgrp —
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 process identified by pid is
returned by
getpgid().
If pid is zero, getpgid()
returns the process group of the current process.
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 system 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.
RETURN VALUES
The getpgrp() system call always succeeds.
Upon successful completion, the getpgid() system
call returns the process group of the specified process; otherwise, it
returns a value of -1 and sets errno to indicate the
error.
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() system call 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() suffices, and
the added complexity of the 4.3BSD
getpgrp() has been omitted from POSIX.1. The old
functionality is available from the getpgid() system
call.
ERRORS
The getpgid() system call will succeed
unless:
- [
ESRCH] - there is no process whose process ID equals pid
SEE ALSO
STANDARDS
The getpgrp() system call is expected to
conform to IEEE Std 1003.1-1990
(“POSIX.1”).
HISTORY
The getpgrp() system call appeared in
4.0BSD. The getpgid() system
call is derived from its usage in AT&T System V
Release 4 UNIX.