Running Linux, 5th Edition

Shells

As we said before, logging into the system in console mode puts you into a shell. If your system is configured with a graphical login, logging in brings you to the graphical interface where you can open an xterm (or similar) window in order to get a shell. The shell interprets and executes all your commands. Let's look a bit at different shells before we keep going, because they're going to affect some of the material coming up.

If it seems confusing that Unix offers many different shells, just accept it as an effect of evolution. Believe us, you wouldn't want to be stuck using the very first shell developed for Unix, the Bourne shell. Although it was a very powerful user interface for its day (the mid-1970s), it lacked a lot of useful features for interactive use—including the ones shown in this section. So other shells have been developed over time, and you can now choose the one that best suits your way of working.

Some of the shells available on Linux are as follows:

bash

Bourne Again shell. The most commonly used (and most powerful) shell on Linux. POSIX-compliant, compatible with the Bourne shell, created and distributed by the GNU project (Free Software Foundation). Offers command-line editing, history substitution, and Bourne shell compatibility.

csh

C shell. Developed at Berkeley. Mostly compatible with the Bourne shell for interactive use, but has a very different interface for programming. Does not offer command-line editing, although it does have a sophisticated alternative ...