Question

I have a text file containing lines of data. I can use the following powershell script to extract the lines I’m interested in:

select-string -path *.txt -pattern 'subject=([A-Z\.]+),' 

Some example data would be:

blah blah subject=THIS.IS.TEST.DATA, blah blah blah 

What I want is to be able to extract just the actual contents of the subject (i.e. the ‘THIS.IS.TEST.DATA’ string). I tried this:

select-string -path *.txt -pattern 'subject=([A-Z\.]+),' | %{ $_.Matches[0] } 

But the ‘Matches’ property is always null. What am I doing wrong?

Answer 1

I don’t know why your version doesn’t work. It should work. Here is an uglier version that works.

$p = 'subject=([A-Z\.]+),' select-string -path *.txt -pattern $p | % {$_ -match $p > $null; $matches[1]} 

Explanation:

-match is a regular expression matching operator:

>'foobar' -match 'oo.ar' True 

The > $null just suppresses the True being written to the output. (Try removing it.) There is a cmdlet that does the same thing whose name I don’t recall at the moment.

$matches is a magic variable that holds the result of the last -match operation.