setreuid(3C)                                                   setreuid(3C)

NAME
     setreuid - set real and effective user IDs

SYNOPSIS
     #include <unistd.h>

     int setreuid(uidt ruid, uidt euid);

DESCRIPTION
     setreuid() is used to set the real and effective user IDs of the cal-
     ling 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
     The following error code descriptions are function-specific. You will
     find a general description in introprm2(2) or in errno(5).

     setreuid fails and neither of the user IDs is changed.

     EINVAL    The value of the ruid or euid argument is invalid or out-
               of-range.

     EPERM     The calling process' 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
     exec(2), getuid(2), setuid(2), setregid(3C), unistd(4).




Page 1                       Reliant UNIX 5.44                Printed 11/98