pnmtile --version (return code: 0)
pnmtile: Using libpbm from Netpbm Version: Netpbm 10.0
pnmtile: BSD defined
pnmtile: RGB_ENV='RGBDEF'
pnmtile: RGBENV= 'RGBDEF' (env vbl is unset)
pnmtile -h (return code: 1)
usage: pnmtile width height [pnmfile]