Can someone optimize my .net RegEx for Powershell - parsing a table with errors-CodePudding

Currently I am trying to parse a table from a Microsoft Site (the GitHub Version of it) to get proper PowerShell Objects. I'll share the relevant code part so you can test it. It does parse what i want but i want the results to be already trimmed (no leading trailing spaces or line-breaks). I also have to get the result for "CNG Key Isolation" which has a different formatting. Only for that block of data my RegEx includes line breaks and I did not get it to work. I know I could do some parsing in PowerShell after the RegEx, but I want to get better with RegEx.

My not yet optimized RegEx looks like this

(?:^##\s*(?<ServiceTitle>[^\r\n#]*)[\r\n\s]*\|\s Name\s \|\s Description\s \|(?:[\r\n\s\|\-\*] Service name[\|\*\s] (?<ServiceName>[^\|]*?)(?: ?\|)|[\r\n\s\|\-\*] Description[\|\*\s] (?<Description>[^\|]*?)(?: ?\|)|[\r\n\s\|\-\*] Installation[\|\*\s] (?<Installation>[^\|]*?)(?: ?\|)|[\r\n\s\|\-\*] Startup type[\|\*\s] (?<StartupType>[^\|]*?)(?: ?\|)|[\r\n\s\|\-\*] Recommendation[\|\*\s] (?<Recommendation>[^\|]*?)(?: ?\|)|[\r\n\s\|\-\*] Comments[\|\*\s] (?<Comments>[^\|]*?)(?: ?\|))*)

You can test it here: https://regex101.com/r/xQDRCO/1

The data to parse comes from: https://raw.githubusercontent.com/MicrosoftDocs/windowsserverdocs/main/WindowsServerDocs/security/windows-services/security-guidelines-for-disabling-system-services-in-windows-server.md

It should basically take one block of data for each service and try to get

"ServiceTitle","ServiceName","Description","Installation","StartupType","Recommendation","Comments"

No matter what order they are or if one of them is missing. "ServiceTitle" is something special and has to be there.

Here is the PowerShell code I currently tested:

$fields = "ServiceTitle","ServiceName","Description","Installation","StartupType","Recommendation","Comments"
$RequestData = Invoke-WebRequest -UseBasicParsing -Uri https://raw.githubusercontent.com/MicrosoftDocs/windowsserverdocs/main/WindowsServerDocs/security/windows-services/security-guidelines-for-disabling-system-services-in-windows-server.md
$RegExMatches = [Regex]::Matches($RequestData.content,'(?:^##\s*(?<ServiceTitle>[^\r\n#]*)[\r\n\s]*\|\s Name\s \|\s Description\s \|(?:[\r\n\s\|\-\*] Service name[\|\*\s] (?<ServiceName>[^\|]*?)(?: ?\|)|[\r\n\s\|\-\*] Description[\|\*\s] (?<Description>[^\|]*?)(?: ?\|)|[\r\n\s\|\-\*] Installation[\|\*\s] (?<Installation>[^\|]*?)(?: ?\|)|[\r\n\s\|\-\*] Startup type[\|\*\s] (?<StartupType>[^\|]*?)(?: ?\|)|[\r\n\s\|\-\*] Recommendation[\|\*\s] (?<Recommendation>[^\|]*?)(?: ?\|)|[\r\n\s\|\-\*] Comments[\|\*\s] (?<Comments>[^\|]*?)(?: ?\|))*)',[System.Text.RegularExpressions.RegexOptions]::Multiline)
$FullList = @()
foreach ($entry in $RegExMatches) {$ServiceAsObject = [pscustomobject]@{};foreach ($field in $fields) {$ServiceAsObject | Add-Member -MemberType NoteProperty -Name $field -Value $entry.Groups[$field].value};$FullList  = $ServiceAsObject}
$FullList[15..17] # three items to see what problem i have with "CNG Key Isolation"

I am not using larger RegEx like that one often, so feel free to give me some feedback to improve myself.

Thank you, An-Dir

CodePudding user response：

This may not be what you are looking for, but you could do something like the following to output an array of custom objects:

$output = switch -regex ($requestdata.content -split '\r?\n') {
    '^##\s' {
        # tracking empty lines since there is one under the service title
        # start new hash table when a new service is found
        # remove ## from service title names
        $emptyLineCount = 0
        $hash = [ordered]@{}
        $hash.ServiceTitle = $_ -replace '^##\s'
    }
    '\| \*\*' {
        # split on | and surrounding spaces
        # replace ** so name is cleaner
        $key,$value = ($_ -split '\s*\|\s*' -replace '\*\*')[1,2]
        $hash[$key] = $value
    }
    '^$' {
        # when second empty line is reached in a service block, output object
        if ($hash.ServiceTitle -and   $emptyLineCount -eq 2) {
            [pscustomobject]$hash
        }
    }
}

# Finding a service by title
$output | Where ServiceTitle -eq 'CNG Key Isolation'

Splitting the contents makes an array of lines, which is easier for me to use switch statement.

CodePudding user response：

Assuming you have all that text in your $RequestData.content, then I wouldn't try to create one large regex to parse it all out into usable objects, but instead would do:

# first split the tables from the rest of the text and work on the table lines only
$result = ($RequestData.content -split '(?m)^The following tables.*:')[-1].Trim() -split '(?m)^## ' | 
    Where-Object { $_ -match '\S' } |
    ForEach-Object {
        # split each block to parse out the title and the table data
        $title, $table = ($_.Trim() -split '(\r?\n){2}', 2).Trim()
        # now remove the markdown stuff from the data and convert it using ConvertFrom-Csv
        $data = (($table -replace '(?m)^\|--\|--\||[*]{2}|^\||\|$' -replace '\s\|\s', '|') -split '\r?\n' -ne '').Trim()  | ConvertFrom-Csv -Delimiter '|'
        # set up an ordered Hashtable to store the data
        $hash = [ordered]@{ServiceTitle = $title}
        foreach ($item in $data) {
            $hash[$item.Name] = $item.Description
        }
        # output real objects
        [PsCustomObject]$hash
    }

$result