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 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 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() call always succeeds. Upon
successful completion, the getpgid() 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() 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() 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
getpgid() will succeed unless:
- [
ESRCH] - there is no process whose process ID equals pid
SEE ALSO
STANDARDS
The getpgrp() function call is expected to
conform to IEEE Std 1003.1-1990
(“POSIX.1”).
HISTORY
The getpgrp() function call appeared in
4.0BSD. The getpgid()
function call is derived from its usage in System V Release 4.