pnmhistmap --version (return code: 0)
pnmhistmap: Using libpbm from Netpbm Version: Netpbm 10.0
pnmhistmap: BSD defined
pnmhistmap: RGB_ENV='RGBDEF'
pnmhistmap: RGBENV= 'RGBDEF' (env vbl is unset)
pnmhistmap -h (return code: 1)
usage: pnmhistmap [-white] [-black] [-max maxvalue] [-verbose] [pnmfile]