Learning the bash Shell, Second Edition

Getting bash

You may or may not be using bash right now. Your system administrator probably set your account up with whatever shell he or she uses as the “standard” on the system. You may not even have been aware that there is more than one shell available.

Yet it’s easy for you to determine which shell you are using. Log in to your system and type echo $SHELL at the prompt. You will see a response containing sh, csh, ksh, or bash; these denote the Bourne, C, Korn, and bash shells, respectively. (There’s also a chance that you’re using another shell such as tcsh.)

If you aren’t using bash and you want to, then you first need to find out if it exists on your system. Just type bash. If you get a new prompt consisting of some information followed by a dollar-sign (e.g: bash2-2.01$ ), then all is well; type exit to go back to your normal shell.

If you get a “not found” message, your system may not have it. Ask your system administrator or another knowledgeable user; there’s a chance that you might have some version of bash installed on the system in a place (directory) that is not normally accessible to you. If not, read Chapter 11, to find out how you can obtain a version of bash.

Once you know you have bash on your system, you can invoke it from whatever other shell you use by typing bash as above. However, it’s much better to install it as your login shell, i.e., the shell that you get automatically whenever you log in. You may be able to do the installation by yourself. Here are instructions ...