setreuid(3)             (BSD Compatibility Package)             setreuid(3)


   NAME
         setreuid - set real and effective user IDs

   SYNOPSIS
         cc [ flag... ] file ... -lucb

         int setreuid(ruid, euid)
         int ruid, euid;

   DESCRIPTION
         setreuid is used to set the real and effective user IDs of the
         calling process.  If ruid is -1, the real user ID is not changed; if
         euid is -1, the effective user ID is not changed.  The real and
         effective user IDs may be set to different values in the same call.

         If the effective user ID of the calling process is super-user, the
         real user ID and the effective user ID can be set to any legal value.

         If the effective user ID of the calling process is not super-user,
         either the real user ID can be set to the effective user ID, or the
         effective user ID can either be set to the saved set-user ID from
         execv or the real user ID. Note: if a set-UID process sets its
         effective user ID to its real user ID, it can still set its effective
         user ID back to the saved set-user ID.

         In either case, if the real user ID is being changed (that is, if
         ruid is not -1), or the effective user ID is being changed to a value
         not equal to the real user ID, the saved set-user ID is set equal to
         the new effective user ID.

   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
         setreuid will fail and neither of the user IDs will be changed if:

         EPERM          The calling process's effective user ID is not the
                        super-user and a change other than changing the real
                        user ID to the effective user ID, or changing the
                        effective user ID to the real user ID or the saved
                        set-user ID, was specified.

   SEE ALSO
         setregid(3)

         exec(2), getuid(2), setuid(2) in the Programmer's Reference Manual.






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