#include <sys/types.h>

gid = getgid()
gid_t gid;

egid = getegid()
gid_t egid;

 DESCRIPTION
 Getgid returns the real group ID of the current process,
 getegid the effective group ID.

The real group ID is specified at login time.

The effective group ID is more transient, and determines
additional access permission during execution of a
``set-group-ID'' process, and it is for such processes
that getgid is most useful.
 "SEE ALSO"
getuid(2), setregid(2), setgid(3)