You can use a "real" programming language for anything more complicated than running a program with some parameters. Really, the only thing the various Shell variants have going for them is that you can type it directly into the console. For any lightly complicated programming task they are abysmal languages.
Quite right! But approximate experiments and lightweight automation are really useful in deciding where to go and then making sure you stay there. I'm all for test-first, but I'd find it very hard to argue that it's a more important tool than, well, scripting things.
Shell scripting is just one option for scripting, some popular (and IMO better) options are Perl, Python and JavaScript.
I'm sure there are also people who use C for quick and dirty tasks. Seems weird, yes. But if that is the language you know best it may be the fastest in the short term.
