Powershell Select-String: Get results by named regex group

Question

I have this Select-String using a regex containing a named group

$m=Select-String -pattern '(?<mylabel>error \d*)' -InputObject 'Some text Error 5 some text'

Select-String does its job:

PS > $m.Matches.groups


Groups   : {0, mylabel}
Success  : True
Name     : 0
Captures : {0}
Index    : 10
Length   : 7
Value    : Error 5

Success  : True
Name     : mylabel
Captures : {mylabel}
Index    : 10
Length   : 7
Value    : Error 5

I can get the value of the matching named group by using the index of the group, no problem:

PS > $m.Matches.groups[1].Value
Error 5

But I have no success in getting the same result by using the named regex group (mylabel). I found statements like $m.Matches.groups["mylabel"].Value but that doesn't work on my machines (W10/W2012, PS 5.1)

unless you have a need for something special that only Select-String can provide, use the vanilla -match instead. this 'Some text Error 5 some text' -match '(?<mylabel>error \d*)' gives this $Matches.mylabel with finally gives this Error 5. — Lee_Dailey
– Lee_Dailey, Commented Feb 22, 2019 at 10:49
@Lee_Dailey I have a reason to use Select-String. My real world script searches potentially hundreds of log files for errors Get-ChildItem d:\logs\*.log -recurse | Select-String -pattern '<regex>' — Gert Jan Kraaijeveld
– Gert Jan Kraaijeveld, Commented Feb 22, 2019 at 10:52
the problem was the wrong place for your Groups property. [grin] use this instead $m.Matches[0].Groups['mylabel']. — Lee_Dailey
– Lee_Dailey, Commented Feb 22, 2019 at 11:00
@Lee_Dailey Thanks! Big jaw dropper for me is that it is necessary to index into Matches $m.Matches[0] here while when using the numerical index of the regex group things works without that. — Gert Jan Kraaijeveld
– Gert Jan Kraaijeveld, Commented Feb 22, 2019 at 11:09
you are welcome! the problem was the way that PoSh will give you an array of the properties from a collection when you use $Collection.PropName the result can be a tad strange. [grin] — Lee_Dailey
– Lee_Dailey, Commented Feb 22, 2019 at 11:11

Ben Richards · Accepted Answer · 2019-02-22 15:15:13Z

3

You got one correct answer in the comment above, but here is how to do it without using the 0 match index:

$m.Matches.groups | ? { $_.Name -eq 'mylabel' } | Select-Object -ExpandProperty Value

answered Feb 22, 2019 at 15:15

Ben Richards

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dan-gph · Accepted Answer · 2025-08-07 01:04:14Z

0

Here's a one-liner:

Select-String -Pattern '(?<mylabel>error \d*)' -InputObject 'Some text Error 5 some text' |
  Select-Object -ExpandProperty Matches |
  ForEach-Object {$_.Groups['mylabel'].Value}

The output:

Error 5

edited Aug 7 at 1:04

answered Aug 7 at 0:55

dan-gph

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js2010 · Accepted Answer · 2025-08-08 16:21:31Z

0

This works for me. I only get one match.

'Some text Error 5 some text' | select-string '(?<mylabel>error \d*)' | 
  % matches | % value

Error 5

Using the -match operator seems to give you the hashtable you want. I'm not sure how to do that with select-string.

'Some text Error 5 some text' -match '(?<mylabel>error \d*)'
$matches.mylabel

Error 5

Here it is with select-string, somewhat awkwardly. You must reference matches[0], then groups is a GroupCollection object with string indexes. Usually there's multiple labels to use in the place of numbers. You wouldn't need the .value in a string context.

$m='Some text Error 5 some text' | Select-String '(?<mylabel>error \d*)'
$m.matches[0].groups['mylabel'].value

Error 5

edited Aug 8 at 16:21

answered Aug 7 at 18:29

js2010

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