set real and effective user
The real and effective user IDs of the current process are set according to the arguments. The saved user ID will be set to the new value of the real user ID if a real user ID is specified and either the new real user ID value is different from the current value or the effective user ID is changed to a value other than the current saved user ID.
Unprivileged users may change either user ID to the current value of the real, effective, or saved user ID. Only the superuser may make other changes.
Supplying a value of -1 for either the real or effective user ID forces the system to substitute the current ID in place of the -1 parameter.
function was intended to allow swapping 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 of the
When setting the real and effective user IDs to the same value, the setuid(2) function is preferred.
Upon successful completion, a value of 0 is returned. Otherwise, a value of -1 is returned and errno is set to indicate the error.
- The current process is not the superuser and a change other than changing the effective user ID to the real user ID was specified.
getuid(2), seteuid(2), setregid(2), setresuid(2), setuid(2)
setreuid() function conforms to the
IEEE Std 1003.1-2001 (“POSIX.1”) and
setreuid() system call first appeared
in 4.1cBSD. A semantically different version
appeared in 4.4BSD. The current version, with the
original semantics restored, appeared in OpenBSD
setreuid() function predates POSIX
saved user IDs. This implementation changes the saved user ID to the new
value of the real user ID only if the real user ID is specified and either
changed or the effective user ID is changed to a value other than the
current saved user ID. Other implementations may behave differently.