setreuid(2)

NAME
     setreuid - set real and effective user ID's

SYNOPSIS
     #include <unistd.h>

     int setreuid (uid_t ruid, uid_t euid);

DESCRIPTION
     The real and effective user ID's of the current process are set according
     to the arguments.  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 vice-versa; only the super-user may make other
     changes.

RETURN VALUE
     Upon successful completion, a value of 0 is returned.  Otherwise, a value
     of -1 is returned and errno is set to indicate the error.

ERRORS
     [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.

SEE ALSO
     getuid(2), setregid(2), setuid(2).