Description

   If the calling process is not already a session leader, setpgrp
   sets the process group ID of the calling process to the process
   ID of the calling process. If setpgrp creates a new session, then
   the new session has no controlling terminal.

   The setpgrp function has no effect when the calling process is a
   session leader.

   This function requires that long (32-bit) UID/GID support be
   enabled. See 32-Bit UID and GID Macro (Integrity servers, Alpha)
   for more information.