PowerShell Pipeline

Regular Expressions I Use with PowerShell

From validating IP addresses to phone numbers, these are some of the handiest expressions in Boe's PowerShell toolbox. What are yours?

• By Boe Prox
• 02/20/2018

As this article states, I want to show some of the regular expressions that I use during my day-to-day activities.

But this isn't just about me and what I use them for. I would love to see what you in the PowerShell community do with regular expressions; share what you do in the comments below so others can benefit from everyone's amazing work!

IP Address Validation/Finding
If you recall, I previously wrote an article on using regular expressions to locate data and even offered up a regular expression to handle finding IP addresses. The RegEx expression that I found (because I didn't want to show off a simple one that could easily be defeated) is shown below:

^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$ 

Using it in a few PowerShell commands shows that it not only works, but also handles values that are out of range.

Splitting a String by Nth Character
If you have a string of characters and need to split it into groups of a particular count of characters, RegEx can make this very simple to do.

(?<>

In this example, I will split up a string of characters into groups of three. This is useful if you have to do some formatting of a MAC address from a single string of 16 characters so you can add colons or a dash. A few examples are below of where I will use the –Split operator instead of the usual –Match as I want to split the data up instead of trying to find something:

E-Mail Addresses
Whether it is validating an e-mail address on a tool that I wrote to create user accounts or searching a text document for e-mail addresses, a good regular expression to work with e-mail addresses is always in my toolkit.

As with validating an IP address, this can either be simple or complex depending on your requirements. Since an e-mail address in itself can be something simple or long and complex, I am going to show a simple RegEx that I use most of the time to locate addresses within a text file.

^[A-Z0-9_\-.]+@[A-Z0-9.-]+$ 

This simple expression will handle some of the possible characters and ensure that it follows a <username @ domain . com> notation.

North American Phone Numbers
Creating Active Directory accounts usually involves adding a phone number for a person's office. If you have a tool written to automate this process, something you might have need of is a way to validate that a phone number given is actually formatted properly or contains all of the necessary numbers to be a valid number.

My RegEx example below is something that I use as a validator in a tool to ensure that the proper number is given.

Note that this one is based on a particular need for myself so your mileage may vary with this example.

^\([0-9]{3}\)\s[0-9]{3}-[0-9]{4}$ 

As long as phone numbers used in my tool meet this requirement, they will be allowed.

Note that while the number was a valid phone number, it was not valid for the requirements that I have on my tool to create accounts that were given to me by management.

Those were some of my examples that I use during my time at work. This was only just a handful of the regular expressions, but I am more interested to see what you in the community have written and use. Please make sure to comment below with your examples so everyone can learn and use your examples!