ABSTRACT
The Shell is more than just an interactive command interpreter. It also defines a simple programming language. A program written in this language is known as a Shell procedure or Shell script, which, in its simplest form, is just a sequence of commands in a file. The file, when executed, performs the tasks as if each command in the script had been entered and executed individually, but without all the typing. Shell scripts can save you a lot of time if you find yourself repeating a sequence of commands over and over. The Shell language also provides variables, control structures such as if-then-else, looping, function definition, and means for input and output. If a particular task can be achieved by combining existing commands, then consider writing a Shell script to do the job.
