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