Table of Contents
header file: unistd.h
pid_t getpgrp(void);
N/A
getpgrp() returns the process group ID.
There is no similar function to getpgrp() in Windows, as process groups do not exist in Windows as they do in Unix.
http://www.opengroup.org/onlinepubs/000095399/functions/getpgrp.html
Informit article on process groups in Windows