SETREUID(2) System Calls Manual SETREUID(2)
setreuid -- set real and effective user ID's
Standard C Library (libc, -lc)
setreuid(uid_t ruid, uid_t euid);
This interface is made obsolete by the saved ID functionality in
setuid(2) and seteuid(2).
The real and effective user ID's of the current process are set according
to the arguments. If the real user ID is changed, the saved user ID is
changed to the new value of the effective user ID.
If ruid or euid 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 may change the effective user ID to the real user ID or the saved
user ID; only the super-user may make other changes.
The setreuid() function 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 of the seteuid()
function (see setuid(2)).
When setting the real and effective user IDs to the same value, this
function is equivalent to the setuid() function. When setting only the
effective user ID, this function is equivalent to the seteuid() function.
Upon successful completion, a value of 0 is returned. Otherwise, a value
of -1 is returned and errno is set to indicate the error.
[EPERM] 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.
getuid(2), seteuid(2), setgid(2), setuid(2)
The setreuid() function call appeared in 4.2BSD. An incompatible version
was implemented in 4.4BSD. It was reimplemented in NetBSD 1.2 in a way
compatible with 4.3BSD, SunOS and Linux, but should not be used in new
NetBSD 6.1.5 January 5, 2001 NetBSD 6.1.5