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Accepted
Doug Chase
Asked: 2011-12-09 09:51:30 +0800 CST

How can I count instances of a regex match in a log file using PowerShell?

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I have a very large log file in which I need to count the occurrences of all the variations of a particular string; that is:

There are a large number of file IDs that appear in the format AA000####. I have to find out what the top five or ten IDs are in this file (which ones appear the most times).

I figure this can be done with select-string and regular expressions?

log-files powershell regex

2 Answers

  1. Best Answer

    If you want to break out just the title portion (which I'm guessing you do) and not group based on the whole URL (which could contain information specific to that visit) you need to get the value of the title parameter like so:

    get-content "test.txt" | % {if($_ -match 'title=([^\&]+)') {$($Matches[1])}} | group | sort -desc Count
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  2. This is off the top of my head but you should be able to do this with a one-liner.

    You can either shove it in a variable and get the length of that variable like so: 

    $count = get-content .\test.txt | select-string -pattern "AA000"
$count.length

    Or our can just do it all inline by using parens: 

    (get-content .\test.txt | select-string -pattern "AA000").length

    You can do you top count with the group-object cmdlet. 

    get-content .\test.txt | group-object | export-csv out.csv

    That is pretty ugly right now, but you should be able to go from there

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