3.2.55 getpgrp

getpgrp 

PID

This function returns the current process group for the specified PID (use a PID of 0 for the current process). Invoking getpgrp will produce a fatal error if used on a machine that doesn't implement getpgrp (2). If PID is omitted, the function returns the process group of the current process (the same as using a PID of 0). On systems implementing this operator with the POSIX getpgrp (2) system call, PID must be omitted or, if supplied, must be 0.