PowerShell Regular Expressions Replace text with dynamic value using a MatchEvalutor
Example
Sometimes you need to replace a value matching a pattern with a new value that's based on that specific match, making it impossible to predict the new value. For these types of scenarios, a MatchEvaluator can be very useful.
In PowerShell, a MatchEvaluator is as simple as a scriptblock with a single paramter that contains a Match-object for the current match. The output of the action will be the new value for that specific match. MatchEvalutor can be used with the [Regex]::Replace() static method.
Example: Replacing the text inside () with it's length
#Sample text
$text = @"
This is (a) sample
text, this is
a (sample text)
"@
#Sample pattern: Content wrapped in ()
$pattern = '(?<=\().*?(?=\))'
$MatchEvalutor = {
param($match)
#Replace content with length of content
$match.Value.Length
}
Output:
> [regex]::Replace($text, $pattern, $MatchEvalutor)
This is 1 sample
text, this is
a 11
Example: Make sample upper-case
#Sample pattern: "Sample"
$pattern = 'sample'
$MatchEvalutor = {
param($match)
#Return match in upper-case
$match.Value.ToUpper()
}
Output:
> [regex]::Replace($text, $pattern, $MatchEvalutor)
This is (a) SAMPLE
text, this is
a (SAMPLE text)
