Understanding Scripting Variables

I’ve already told you a bit about scripting variables, and you’ve already seen them in use. But, there’s a bit more to the story.

Creating and Deleting Variables

As you’ve already seen, it’s sometimes either necessary or more convenient to define variables in your scripts. You can also define, view, and unset variables from the command-line. Here’s an example:

[donnie@fedora ~]$ car=Ford
[donnie@fedora ~]$ echo $car
Ford
[donnie@fedora ~]$ unset car
[donnie@fedora ~]$ echo $car
[donnie@fedora ~]$

Here, I’ve defined the variable car, and set its value to Ford. The first echo command shows the assigned value. The second echo command verifies that I’ve successfully cleared the variable with unset.

Understanding Variables and Shell Levels

When you place a shebang line, such as #!/bin/bash or #!/bin/sh, at the start of your script, a new non-interactive child shell will be...