Powershell regex group : how do I get all subgroups 2-CodePudding

I want to extract file1, file2 I know how to do this in javascript, I'm lost in Powershell, I can only extract the whole second match following that tut https://devblogs.microsoft.com/scripting/regular-expressions-regex-grouping-regex/, what's the syntax ?

  $regex = '(. \\)*(. )\.(. )$'
  $data = @'
  "C:\test\file1.txt"
  "C:\test\file2.txt"
  '@
  [RegEx]::Matches($data,$regex).value

CodePudding user response：

Here is how you could do it using the call to Regex.Matches:

$data = @'
"C:\test\file1.txt"
"C:\test\file2.txt"
'@

$regex = [regex] '(. \\)*(?<base>. )\.(. )'
$regex.Matches($data).ForEach{ $_.Groups['base'] }.Value

# Results in:
# file1
# file2

However since you're dealing with paths, I would personally recommend you to use FileInfo class to parse the paths. In this example, we can use the String .Trim(Char) Method to remove the leading and trailing " from each path and the -as Type Operator to safely convert the strings into System.IO.FileInfo instances.

$data = (@'
"C:\test\file1.txt"
"C:\test\file2.txt"
'@ -split '\r?\n').Trim('"') -as [IO.FileInfo[]]

$data.BaseName

CodePudding user response：

An example of using -match and the $matches automatic variable to retrieve capture group values:

$data = @'
"C:\test\file1.txt"
"C:\test\file2.txt"
'@

$data -match '\\([^.\\] )\.[\s\S] ?\\([^.\\] )\.'

write-host $matches[1]    # file1
write-host $matches[2]    # file2

CodePudding user response：

Just for completeness another RegEx solution:

$data = @'
"C:\test\file1.foo.txt"
"C:\test\file2.bar.txt"
'@

[regex]::Matches($data, '[^\\] (?=\.. )').Value

Output:

file1.foo
file2.bar

The RegEx uses a positive lookahead (?=) to assert that an extension follows, without capturing it.

Detailed explanation at regex101.

I still think that the FileInfo solution is more robust and easier to maintain.