Although Unix shells make no distinction between commands entered from the keyboard and those input from a script, there are certain shell features that are meant for scripting and not convenient or useful to use interactively.

Many of these features will be familiar to anyone who has done any computer programming. They include constructs such as comments, conditionals and loops.

The following sections provide a very brief introduction to shell constructs that are used in scripting, but generally not used on the command line.