PowerShell Regex Groupies

named

            April 4, 2024

        PowerShell Regex Groupies

            Learn how to use regular expression named captures  in PowerShell to extract data from log files, and created custom objects for structured data storage.

            My friend Gladys reached out the other day for help with a regular expression problem. She told me she was trying to do use capture groups with data from a log file using PowerShell. I assumed she was using a regex pattern to defined *named* captures. This is a technique where you can assign a name to the matching text in a capture group. This makes it easier to reference the captured text later in your script. The more information I learned from her, the more I realized the term she was using didn't mean what she thought it did.

But her problem is not unique and I thought offered a terrific "learning opportunity." Ultimately, named captures will work for her, but she had some additional challenges at well. Let's work through the problem.

## Named Captures

I will use this string as an example.

$t = "198274-banana_foo:monkey"

You might have a log file with lines of structured data that you want to parse. I recommend that when you are working with regular expressions in PowerShell, think about creating object output and not focusing merely on matching text.

In my silly example, I want to break the string into several parts:

- Number (198274)

- Fruit (banana)

- Animal (monkey)

Here is a regular expression pattern that will match the string and capture the parts I want.

[regex]$rx = "(?\d+)-(?\w+)_\w+:(?\w+)"

The named capture is the part in parentheses. You can define a name for each pattern. The first pattern I am searching for is 1 or more digits (`\d+`). Before this pattern I define a name using the syntax `?)`.

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My friend Gladys reached out the other day for help with a regular expression problem. She told me she was trying to do use capture groups with data from a log file using PowerShell. I assumed she was using a regex pattern to defined named captures. This is a technique where you can assign a name to the matching text in a capture group. This makes it easier to reference the captured text later in your script. The more information I learned from her, the more I realized the term she was using didn't mean what she thought it did.
But her problem is not unique and I thought offered a terrific "learning opportunity." Ultimately, named captures will work for her, but she had some additional challenges at well. Let's work through the problem.
Named Captures

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PowerShell Regex Groupies

Learn how to use regular expression named captures in PowerShell to extract data from log files, and created custom objects for structured data storage.

Named Captures