|SETREUID(2)||System Calls Manual||SETREUID(2)|
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.
setreuid() 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 seteuid(2)
When setting the real and effective user IDs to the same value, the setuid(2) function is preferred.
setreuid() function conforms to the IEEE Std 1003.1-2008 (“POSIX.1”) specification, except that the conditions for changing the saved user ID differ and that, if it is changed, the saved user ID is set to the real user ID instead of the effective user ID.
setreuid() system call first appeared in 4.1cBSD, predating POSIX. A semantically different version appeared in 4.4BSD. The current version, with the original semantics restored, appeared in OpenBSD 3.3.
|February 5, 2015||OpenBSD-current|