ppmbrighten --version (return code: 0)
ppmbrighten: Using libpbm from Netpbm Version: Netpbm 10.0
ppmbrighten: BSD defined
ppmbrighten: RGB_ENV='RGBDEF'
ppmbrighten: RGBENV= 'RGBDEF' (env vbl is unset)
ppmbrighten -h (return code: 1)
usage: ppmbrighten [-saturation <+-s>] [-value <+-v>] [-normalize] [<ppmfile>]