Each executable file in a Unix file system is associated with a set-user-ID bit and a set-group-ID bit. If the set-user-ID bit and/or the set-group-ID bit is set, then the effective user ID and/or group ID of the process is set to the owner ID and/or group ID of the executable file upon execution.
In a network environment, if an executable file is part of a file system which supports execute/search permissions (see sec. 4.2.2), the administrator of a client may have disabled the set-user/group-ID capability as a security precaution. An application should be able to determine for a particular executable file whether the file's set-user/group-ID capability is functional.