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SETREUID(2)                 BSD System Calls Manual                SETREUID(2)

     setreuid -- set real and effective user IDs

     Standard C Library (libc, -lc)

     #include <unistd.h>

     setreuid(uid_t ruid, uid_t euid);

     The real and effective user IDs 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 effec-tive effective
     tive user ID and vice-versa; 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, the stan-dard standard
     dard setuid() function is preferred.

     The setreuid() function returns the value 0 if successful; otherwise the
     value -1 is returned and the global variable errno is set to indicate the

     [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), issetugid(2), seteuid(2), setuid(2)

     The setreuid() system call appeared in 4.2BSD.

BSD                            February 8, 2001                            BSD