The command line functionality on Mac and Linux are indeed similar as OS X has a flavour of UNIX (called Darwin) underneath the GUI that you see.
The default shell on OS X is bash, so if you're familiar with that you will adjust nicely.
On a Mac, the default command line application is Terminal. There are also a number of other emulators out there but overall Terminal provides a very similar look and feel to the shell you are used to in Linux.
The primary source of differences though are:
- Different command line arguments at times (i.e. see
du for example). The primary commands like
ls etc. are similar.
- There are more parts of OS X that shouldn't be edited by hand as you might do in Linux. This is a topic of its own, but just be aware that running a Mac is not exactly like running a Linux box in terms of configuration and upkeep.
That being said there are also a lot of cool hacks available from the command line in OS X (e.g.
open commnand). There are lots of previous threads and blog posts out there with more info.
You can also get your hands on a bunch of opensource packages (i.e.
hg, etc.) via MacPorts, Fink or a few other package management systems for OS X. You can also build other source packages intended for UNIX/Linux like systems as necessary.