set real and effective user ID's
Standard C Library (libc, -lc)
The real and effective user IDs of the current process are set according to the
arguments. If ruid
is -1, the current uid is filled in by
the system. Unprivileged users may change the real user ID to the effective
user ID and vice-versa; only the super-user may make other changes.
If the real user ID is changed (i.e. ruid
not -1) or the effective user ID is changed to something other than the real
user ID, then the saved user ID will be set to the effective user ID.
() system call has been used to
swap the real and effective user IDs in set-user-ID programs to temporarily
relinquish the set-user-ID value. This purpose is now better served by the use
When setting the real and effective user IDs to the same value, the standard
() system call is preferred.
() function returns the
value 0 if successful; otherwise the value -1 is returned and
the global variable errno
is set to indicate
- The current process is not the super-user and a change other than changing
the effective user-id to the real user-id was specified.
() system call appeared in