Chapter 8. Shell Programming

Chapter Objectives The meaning of variables and different types of shell variables Writing shell scripts Executing shell scripts How to make shell scripts interactive using the read command Positional parameters, their usage to read command line arguments and their manipulation The exit status and performing various types of tests Decision making and loop-control statements Integer computing and string handling using expr Performing real arithmetic Debugging scripts Recording a session using the script command Having a working environment according one's taste using .profile

One of the important components of all Unix systems is the shell, which acts as a command processor as well as a programming language. We have chiefly seen it as a command processor in the previous chapters. As shell is a programming language too, one can write programs using it. Such programs are called shell programs. More often shell programs are referred to as shell scripts. This chapter primarily discusses how shell programs are written and executed. Many shell scripts that have been executed and tested have been included towards the end of this chapter.