VMS Help SPAWN, Qualifiers, /OUTPUT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /OUTPUT=filespec

    Specifies the output file to which the results of the SPAWN
    operation are written. The asterisk (*)  and the percent sign (%)
    wildcard characters cannot be used in the file specification.
    (Do not specify SYS$COMMAND as a file specification for the
    /OUTPUT qualifier when using the /NOWAIT qualifier; both parent
    and subprocess output will be displayed simultaneously on your
    terminal.)

                                 CAUTION

       If you include a version number in the filespec argument
       of the /OUTPUT qualifier, and that version of the specified
       file already exists, the existing file is replaced with the
       new output.

    You cannot explicitly specify non-record-oriented, process-
    permanent files (NRO PPFs) with the /OUTPUT qualifier. The system
    displays an error message when it encounters such a file as the
    value for the /OUTPUT qualifier.

    Note that when NRO PPFs are used as implicit output, the SPAWN
    command can succeed, as shown in the following table:

    Process
    Type         SYS$OUTPUT   Implicit Output

    Any          NRO PPF      Mailbox transmitting records for parent
                              to write to its current SYS$OUTPUT
                              device

    Any          Any other    SYS$OUTPUT

    If you omit the /OUTPUT qualifier, output is written to the
    current SYS$OUTPUT device.