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GETPGRP(2) BSD System Calls Manual GETPGRP(2)
getpgrp -- get process group
Standard C Library (libc, -lc)
The process group of the current process is returned by getpgrp(). 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.
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.
getpgid() will succeed unless:
[ESRCH] there is no process whose process ID equals pid
getsid(2), setpgid(2), termios(4)
The getpgrp() function call appeared in 4.0BSD. The getpgid() function call is derived from
its usage in System V Release 4.
The getpgrp() function call is expected to conform to ISO/IEC 9945-1:1990 (``POSIX.1'').
This version of getpgrp() differs from past Berkeley versions by not taking a pid_t pid
argument. This incompatibility is required by ISO/IEC 9945-1:1990 (``POSIX.1'').
From the ISO/IEC 9945-1:1990 (``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.
BSD June 4, 1993 BSD
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