setregid(2)

NAME
     setregid - set real and effective group ID

SYNOPSIS
     #include <unistd.h>

     int setregid (gid_t rgid, gid_t egid);

DESCRIPTION
     The real and effective group ID's of the current process are set to the
     arguments.  Unprivileged users may change the real group ID to the
     effective group ID and vice-versa; only the super-user may make other
     changes.

     Supplying a value of -1 for either the real or effective group ID forces
     the system to substitute the current ID in place of the -1 parameter.

RETURN VALUE
     Upon successful completion, a value of 0 is returned.  Otherwise, a value
     of -1 is returned and errno is set to indicate the error.

ERRORS
     [EPERM]        The current process is not the super-user and a change
                    other than changing the effective group-id to the real
                    group-id was specified.

SEE ALSO
     getgid(2), setreuid(2), setgid(3).