— get user identification
() function returns the real user ID of
the calling process. The geteuid
returns the effective user ID of the calling process.
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 execution of
” mode processes,
() is used to determine the real user ID of
the calling process.
() functions are always successful, and no
return value is reserved to indicate an error.
() functions conform to
IEEE Std 1003.1-2008
() system call first appeared in
Version 1 AT&T UNIX
() in Version 7