Note: help and version output are generated by a naïve script which tries a few variants of
<command> --help, <command> -h etc. to find the command's help and version info.
Sometimes it gets lucky, sometimes it doesn't; if the output below looks wrong, it probably is.
pnmtopng --version (return code: 0)
pnmtopng: Using libpbm from Netpbm Version: Netpbm 10.0
pnmtopng: BSD defined
pnmtopng: RGB_ENV='RGBDEF'
pnmtopng: RGBENV= 'RGBDEF' (env vbl is unset)
pnmtopng -HELP (return code: None)