Created attachment 1611 [details]
Patch

If you mistakenly run the command

  ssh-rand-helper 256

expecting it to return 256 bytes of output, ssh-rand-helper silently
ignores the error on the command line and returns 48 bytes of output.
It would be helpful to get an usage message in this case.

Also, if you enter an illegal command line option, say,

  ssh-rand-helper -z

ssh-rand-helper does print a usage message, but it will otherwise
ignore the error and will return an exit status of zero.  It would
seem more prudent to treat this as a fatal error.