Knowing the command line is one of those unsung critical skills of being a software engineer. Doesn't really matter so much what flavor of command line you're using (though bash is great for obvious reasons), but the ability to glue different, disparate commands together through pipes is one of the most efficient ways of getting throwaway work done. Heck, just knowing IFS=$'\n' and how to do a for loop will get you a <i>long</i> way.