GETUID(2) BSD System Calls Manual GETUID(2)
getuid, geteuid -- get user identification
The getuid() function returns the real user ID of the calling process.
The geteuid() function returns the effective user ID of the calling
The real user ID is that of the user who has invoked the program. As the
effective user ID gives the process additional permissions during execu-
tion of ``set-user-ID'' mode processes, getuid() is used to determine the
real-user-id of the calling process.
The getuid() and geteuid() functions are always successful, and no return
value is reserved to indicate an error.
Geteuid() and getuid() functions conform to IEEE Std 1003.1-1988
4th Berkeley Distribution June 4, 1993 4th Berkeley Distribution