| GETPGRP(2) | System Calls Manual | GETPGRP(2) | 
getpgrp, getpgid —
#include <unistd.h>
pid_t
  
  getpgrp(void);
pid_t
  
  getpgid(pid_t
    pid);
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.
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.
getpgrp() always succeeds, however
  getpgid() will succeed unless:
ESRCH]getpgrp() function conforms to IEEE
  Std 1003.1-1988 (“POSIX.1”).
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.
| August 11, 2002 | NetBSD 10.0 |