setreuid(3)        UNIX System V(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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