pbmpscale --version (return code: 0)
pbmpscale: Using libpbm from Netpbm Version: Netpbm 10.0
pbmpscale: BSD defined
pbmpscale: RGB_ENV='RGBDEF'
pbmpscale: RGBENV= 'RGBDEF' (env vbl is unset)
pbmpscale (return code: 1)
usage: pbmpscale scale [pbmfile]