Classic Shell Scripting

Summary

The choice of compiled language versus scripting language is usually made based on the need of the application. Scripting languages generally work at a higher level than compiled languages, and the loss in performance is often more than made up for by the speed with which development can be done and the ability to work at a higher level.

The shell is one of the most important and widely used scripting languages in the Unix environment. Because it is ubiquitous, and because of the POSIX standard, it is possible to write shell programs that will work on many different vendor platforms. Because the shell functions at a high level, shell programs have a lot of bang for the buck; you can do a lot with relatively little work.

The #! first line should be used for all shell scripts; this mechanism provides you with flexibility, and the ability to write scripts in your choice of shell or other language.

The shell is a full programming language. So far we covered the basics of commands, options, arguments, and variables, and basic output with echo and printf. We also looked at the basic I/O redirection operators, <, >, >>, and |, with which we expect you're really already familiar.

The shell looks for commands in each directory in $PATH. It's common to have a personal bin directory in which to store your own private programs and scripts, and to list it in PATH by doing an assignment in your .profile file.

We looked at the basics of accessing command-line arguments and simple execution ...