The humble variable

Powershell has mushroomed recently into almost every facet of systems administration. From Exchange servers to system information management, IT professionals without programming backgrounds are working with scripts more than ever.

The ability to automate almost every aspect of operations is tantalizing. But before we unleash an automated process on critical infrastructure, we should understand what it does.

To that end, let’s look at a fundamental idea: the variable.

Remember when we talked about arrays last month? A series of containers to store your stuff that could be referenced by name or item number?

The variable is even simpler. A variable is a single container that you create. All it has is a name. What is in the container could stay static, or it could change. Think of it like a bucket with a name written on it. The variable name stands for everything in the bucket.

Variables are commonly used in a couple of ways.

The first is to store a value temporarily. This is often present in browser-side scripting like Javascript. If the operations performed on the page don’t really require a big database or even an array, why not just create one bucket to hold that value?

In Javascript, PHP or Powershell, the variable comes into existence as soon as you declare it.

$mybucket = "The text string I'm storing in the variable called mybucket";

In one line, we’ve created a new variable called mybucket and put something inside of it: a string of text. We could just as easily fill it with an integer, a URL or a filename on our web server. From this moment forward, the entire text string can be represented simply by the variable name. Want to change the text in your form field?

document.getElementByID("mytextfield").value = $mybucket;

In Powershell and PHP, declaring a variable also starts with a $ sign.

$rcpath = "c:\users\jimmyjoe\appdata\local\microsoft\outlook\roamcache";

Want to write a script that works with Jimmy Joe in accounting’s Outlook cache for Autocomplete entries, but don’t feel like typing out the entire path every time you want to reference it? Your friend the variable has your back.

So when you’re staring down the unforgiving scramble of an administration script with a bunch of $ signs in it, don’t panic. They’re only buckets, and now you know a little bit more about what they do.