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