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

       /LISTING[=filespec]
       /NOLISTING

    Controls whether an output listing is created and optionally
    provides an output file specification for the listing file.
    A listing file contains a listing of the command definitions
    along with any error messages. The listing file is similar to a
    compiler listing.

    If you specify the /LISTING qualifier and omit the file
    specification, output is written to the default device and
    directory; the listing file will have the same name as the first
    command definition file and a file type of .LIS.

    You can use the /LISTING qualifier only in /OBJECT or /REPLACE
    mode; you cannot create a listing in /DELETE mode. In /OBJECT and
    /REPLACE modes, the default is /NOLISTING.