Library /sys$common/syshlp/pca$help.hlb EXTRACT, Description  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    When you use the EXTRACT command to save the contents of a
    display into a file, only those lines that are currently stored
    in the display's memory buffer (as determined by the /SIZE
    qualifier on the DISPLAY or SET DISPLAY command) are written
    to the file.

    You cannot extract the contents of the PROMPT display into a
    file.