OSX is Unix (posix), and Linux is actually GNU/Linux. Commands on GNU/Linux can normally do what a Unix command can do, but because GNU had to reimplement many of the commands (license issues), then also sometimes have added an option or two which does not exist on Unix. I normally write my scripts on OSX and then move them to GNU/Linux as I then know that they should work, the other way around gives me too much gray hair.
Casper
