What Is the Shell?
The shell provides you with an interface to the UNIX system. It reads input from you and executes the programs you specified. While the programs are executing, it displays their output. For this reason, the shell is often referred to as the UNIX system's command interpreter. For users familiar with Windows, the UNIX shell is similar to the DOS shell, COMMAND.COM.
The real power of the shell lies in the fact that it is much more than a command interpreter. It is also a powerful programming language, complete with conditional statements, loops, and functions.
If you are familiar with these types of statements from other programming languages, you can learn shell programming quickly. If you haven't seen these before, don't fret. ...