pbmmake --version (return code: 0)
pbmmake: Using libpbm from Netpbm Version: Netpbm 10.0
pbmmake: BSD defined
pbmmake: RGB_ENV='RGBDEF'
pbmmake: RGBENV= 'RGBDEF' (env vbl is unset)
pbmmake -h (return code: 1)
usage: pbmmake [-white|-black|-gray] <width> <height>