[OpenBSD]

Manual Page Search Parameters

GETPGRP(2) System Calls Manual GETPGRP(2)

getpgrp, getpgid
get process group

#include <unistd.h>
pid_t
getpgrp(void);
pid_t
getpgid(pid_t pid);

The process group of the current process is returned by getpgrp(). The process group of the pid process 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.
These calls are 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.

getpgrp() always succeeds, however getpgid() will succeed unless:
 
 
[]
The current process and the process pid are not in the same session.
 
 
[]
There is no process with a process ID equal to pid.

setpgid(2), termios(4)

The getpgrp() and getpgid() functions conform to IEEE Std 1003.1-2008 (“POSIX.1”).

A getpgrp() function call that took a pid_t pid argument appeared in 4.0BSD. This version, without an argument, is derived from its usage in System V Release 4, and first appeared in NetBSD 0.9.
The getpgid() function call is derived from its usage in System V Release 4, and first appeared in NetBSD 1.2A.
September 10, 2015 OpenBSD-current