Beginning Shell Scripting

Chapter 1. Introducing Shells

This chapter introduces the shell, obviously the most important component for shell scripting. It describes the choices among shells, as well as how to find out which shells are available. In modern graphical desktop environments, it is not always easy to find the shell, but you'd be surprised at how many systems actually support shells, from Zaurus PDAs to Audrey network appliances to the beautifully designed Mac OS X systems.

No matter how nice a graphical user interface your system sports, adding the power of a shell can dramatically increase the speed and efficiency of what you can do on your computer. Shells provide greater control over your system and allow you to do some things that simply cannot be done from the graphical environment. Shells often allow you to perform tasks remotely, which is especially useful if you need to do something to a large number of computers or computers located at another site.

Even in an environment such as Apple's Mac OS X, shell scripting is a useful, powerful tool in anyone's kit. Apple had the forethought to make it possible to connect shell scripts to the GUI environment via a number of custom utilities that ship with the OS, so you can link UI-level scripts done in AppleScript to the shell environment for more power than either environment alone would have.

Because shells exist to accept your commands, each shell provides help for entering complicated commands, a set of sometimes-complicated shortcuts that can ...