Terminal and shells

In the quick Tutorial I have said the Terminal does this, the Terminal does that. However that was a lie: The Terminal is "just" a Mac Application that can run shells. Unix shells to be precise. There are actually a couple of them. The default one the Mac is called 'bash'. A shell is the program that reads your text, splits the command from the parameters and then executes them. The shell itself can understand a couple of commands. For the rest it will try if it can find a program with the given name. If not, then it will say:

-bash: thisProgramNameCanNotBeFound: command not found

Which is the most common and harmless shell error you will experience. And, again, it's quiet meaningful: "command not found" is pretty straight forward. From now on this site will talk about the 'shell' rather than the terminal. It is noteworthy that the shells under OS X work exactly like their counter parts in any other flavor of Unix.

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