ultrix man page for getpgrp

getpgrp(2)							System Calls Manual							getpgrp(2)

Name
       getpgrp - get process group

Syntax
       #include <sys/types.h>
       #include <unistd.h>

       pgrp = getpgrp(pid)
       pid_t pgrp;
       pid_t pid;

Description
       The system call returns the process group of the specified process.  If pid is zero, the call applies to 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 the foreground and may read, while others block with a signal if they attempt to read.

       This call is used by programs such as to create process groups in implementing job control.  The TIOCGPGRP and TIOCSPGRP calls described in
       are used to get and set the process group of the control terminal.

Environment
       When  your  program  is	compiled  in  the  System V or POSIX environment, is called without arguments and the process group of the current
       process is returned.

       Additionally, in POSIX mode, returns a value type of pid_t.

Diagnostics
       The call fails under the following condition:

       [ESRCH]	      No such process, PID.

See Also
       getuid(2), setpgrp(2), tty(4)

																	getpgrp(2)