pnminterp --version (return code: 0)
pnminterp: Using libpbm from Netpbm Version: Netpbm 10.0
pnminterp: BSD defined
pnminterp: RGB_ENV='RGBDEF'
pnminterp: RGBENV= 'RGBDEF' (env vbl is unset)
pnminterp -HELP (return code: 1)
pnminterp: Wrong number of arguments (0). Without scale options, you must supply 1 or 2 arguments: scale and optional file specification