NAME

getpgrp, getpgid — get process group

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS

#include <unistd.h>

pid_t
getpgrp(void);

pid_t
getpgid(pid_t pid);

DESCRIPTION

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.

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

setpgid(2), termios(4)

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.