To use gnash on the command-line you can use use the command gnash-raymii ~/flash-file.swf.
To use the commands you must prefix them with the snap name. (gnash-raymii.dump-gnash).
GNU Gnash is the GNU Flash movie player — Flash is an animation
file format pioneered by Macromedia which continues to be
supported by their successor company, Adobe. Flash has been
extended to include audio and video content, and programs written
in ActionScript, an ECMAScript-compatible language. Gnash is
based on GameSWF, and supports most SWF v7 features and some
SWF v8 and v9. SWF v10 is not supported by GNU Gnash.