The R_getgroupsbyname service checks the input group count and, if it is zero, returns the number of supplemental groups for the specified user ID. If the input count is not zero and it is less than the number of groups, an error code is returned. If the count is not less than the number of groups, the GIDs of the supplemental groups for the specified user ID are put into the grouplist area, and the number of GIDs is returned.