Why Shell?
In UNIX, which is the parent operating system of Linux and the origin of many of the ideas and of the philosophy of the operating system, a variety of different shell programs are available. The most common on commercial versions of UNIX is probably the Korn shell, but there are many others. So why use a shell to program? Well, the shell leads a double life. Although it has superficial similarities to the Windows command prompt, it’s much more powerful, capable of running reasonably complex programs in its own right. You can not only execute commands and call Linux utilities; you can also write them. The shell uses an interpreted language, which generally makes debugging easier because you can execute single lines, and there’s no recompile time. However, this can make the shell unsuitable for time-critical or processor intensive tasks.
One reason to use the shell for programming is that you can program the shell quickly and simply. Also, a shell is always available even on the most basic Linux installation. So for simple prototyping you can find out if your idea works. The shell is also ideal for any small utilities that perform some relatively simple task where efficiency is less important than easy configuration, maintenance, and portability. You can use the shell to organize process control, so that commands run in a predetermined sequence dependent on the successful completion of each stage.