Library /sys$common/syshlp/sysmanhelp.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 command
    strings that you want executed by the spawned subprocess. If you
    specify a command string along with an input file, the command
    string gets processed before the commands in the input file. When
    processing is complete, the subprocess terminates.