SETREGID(2)
NAME
setregid − set real and effective group ID
USAGE
setregid(rgid, egid)
int rgid, egid;
DESCRIPTION
The real and effective group IDs of the current process are set to the arguments. Only the super-user may change the real group ID of a process. Unprivileged users may change the effective group ID only to the real group ID.
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 zero 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.