/sys$common/syshlp/helplib.hlb SPAWN, Qualifiers, /INPUT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /INPUT=filespec

    Specifies an input file containing one or more DCL commands to
    be executed by the spawned subprocess. The file type defaults
    to .COM. The asterisk (*)  and the percent sign (%) wildcard
    characters are not allowed in the file specification. Once
    processing of the input file is complete, the subprocess is
    terminated. If both a command string and the /INPUT qualifier
    are specified, the specified command string executes before
    additional commands are obtained from the /INPUT qualifier.
    If neither is specified, SYS$INPUT is assumed (in which case a
    SPAWN/NOWAIT command is aborted if Ctrl/Y is pressed to abort
    something running in your parent process).

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

    Note that when NRO PPFs are used as implicit input (that is, the
    /INPUT qualifier is not specified and SYS$INPUT is a NRO PPF),
    the SPAWN command can succeed, as shown in the following table:

    Process Type     SYS$INPUT  Implicit Input

    Interactive      NRO PPF    SYS$COMMAND

    Noninteractive   NRO PPF    Null device

    Any              Any other  SYS$INPUT

    If SYS$INPUT is a terminal, it cannot have an associated terminal
    mailbox.