How do I capture the 2nd match for each line?

Question

Basically, I need to match with 1 per line but right now, my regex is matching 2 per line.

My regex is looking for 2 slashes and it returns the string in between but the problem is my path has multiple slashes and I only need to match it with the 2nd match per each line

(?<=\\).*?(?=\\)

This is my PowerShell code:

if ( $_.PSPath -match ("(?<=::).*?(?=\\)")) {
    $user = $matches.Values
}

For example:

Microsoft.PowerShell.Security\Certificate::CurrentUser\Root\CDD4EEAE6000AC7F40C3802C171E30148030C072
Microsoft.PowerShell.Security\Certificate::CurrentUser\Root\BE36A4562FB2EE05DBB3D32323ADF445084ED656

What my code does is it gets

Certificate::CurrentUserRoot
Certificate::CurrentUserRoot

but what I only really need is get the string to the 2nd match \ ___\ which is:

Root
Root

Emma · Answer 1 · 2019-08-19T21:42:17.900

1

I'm guessing that, maybe an expression similar to,

(?<=\\)[^\\]*(?=\\[A-Z0-9]{40}$)

might be an option to look into.

Demo 1

Or maybe just,

[^\\]*(?=\\[A-Z0-9]{40}$)

or

[^\\]*(?=\\[A-F0-9]{40}$)

would simply return Root and 40 is the length of [A-F0-9] ending substring. For more flexible quantifier, this expression might work:

[^\\]*(?=\\[A-F0-9]*$)

Demo 2

edited Aug 19 '19 at 21:42

answered Aug 19 '19 at 21:09

Emma

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1

Demo 2 works for me. That's really all I need. But what is the 40 for? – 123testing123 Aug 19 '19 at 21:30
2

Does that mean that if its more than 40 characters or less than 40 characters, it won't work? – 123testing123 Aug 19 '19 at 21:35

The fourth bird · Accepted Answer · 2019-08-19T22:09:35.167

1

You could make use of an anchor ^ to assert the start of the string. Repeat 2 times matching not a backslash or a newline followed by a backslash.

Use a capturing group to match what follows;

^[^\\\r\n]*\\[^\\\r\n]*\\([^\\\r\n]+)

About the pattern

^ Start of string
[^\\\r\n]*\\[^\\\r\n]*\\ Match 2 times not \ or a newline, then \
( Capture group 1
- [^\\\r\n]+ Match 1+ times not \ or a newline
) Close group 1

Regex demo | Try it online

The value is in the first capturing group:

$user = $matches[1]

If you want the match only to use your script instead of group 1, you could make use of a positive lookbehind to assert what is on the left is 2 times not \ followed by \

(?<=^[^\\\r\n]*\\[^\\\r\n]*\\)[^\\\r\n]+

Regex demo | Try it online

edited Aug 19 '19 at 22:09

answered Aug 19 '19 at 21:14

The fourth bird

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Thank you. This one actually is outputting the same thing that I currently have. But thank you so much for helping me out. – 123testing123 Aug 19 '19 at 21:30
Your value is in the first capturing group ( highlighted in green in the regex101demo). It does not require a character count. – The fourth bird Aug 19 '19 at 21:32
Ah I see the difference. However, when I try to match this with my powershell script, it only outputs me the first capturing group. – 123testing123 Aug 19 '19 at 21:34
@123testing123 Did you try `$matches.Values[1]` See https://www.regular-expressions.info/powershell.html – The fourth bird Aug 19 '19 at 21:48

score 0 · Answer 3 · answered Aug 22 '19 at 23:43

To offer a pragmatic alternative using PowerShell's -split operator:

PS> 'Microsoft.PowerShell.Security\Certificate::CurrentUser\Root\CDD4EEAE6000AC7F40C3802C171E30148030C072',
'Microsoft.PowerShell.Security\Certificate::CurrentUser\Root\BE36A4562FB2EE05DBB3D32323ADF445084ED656' |
  ForEach-Object { ($_  -split '[::|\\]')[4] }

Root
Root

The above tokenizes each input string by separators \ or ::, and extracts the 4th token.

How do I capture the 2nd match for each line?

3 Answers3

Demo 1

Demo 2