Creating Your Own Commands Using Shell Scripting
Now that you've acquired a sizable amount of experience using the console and the shell; have learned a number of common commands; and are familiar with concepts such as pipes, command substitution, variable substitution, and quoting, it's time to begin creating shell scripts.
A shell script is really a way of automating complex tasks or repetitive sequences of commands that you often carry out at the shell so that you don't have to type these commands over and over each time you want to repeat the task. Often, the sequences of commands in shell scripts are complex enough that your shell scripts really become new commands, tailor-made to your productivity needs.
Structurally, a shell script is ...