Multiple Select Strings in a for loop to separate files

[edit - thanks to mklement0 for pointing out the errors about speed and the -SimpleMatch switch. [grin]]

the Select-String cmdlet will accept a -Path parameter ... and it is FAR [i was thinking of Get-Content, not Get-ChidItem] faster than using Get-ChildItem to feed the files to S-S. [grin]

also, the -Pattern parameter accepts a regex OR pattern like Thing|OtherThing|YetAnotherThing - and it accepts simple string patterns if you use the -SimpleMatch switch parameter.

what the code does ...

• defines the source dir
• defines the file spec
• joins those two into a wildcard file path
• builds an array of string patterns to use
• calls Select-String with a path and an array of strings to search for
• uses Group-Object and a calculated property to group the matches by the last part of .Line property from the S-S call
• saves that to a $Var
• shows that on screen

at that point, you can use the .Name property of each GroupInfo to select the items to send out to each file AND to build your file names.

the code ...

$SourceDir = 'D:\Temp\zzz - Copy'
$FileSpec = '*.log'
$SD_FileSpec = Join-Path -Path $SourceDir -ChildPath $FileSpec

$TargetPatternList = @(
    'Accordion Cajun Zydeco'
    'better-not-be-there'
    'Piano Rockabilly Rowdy'
    )

$GO_Results = Select-String -Path $SD_FileSpec -SimpleMatch $TargetPatternList |
    Group-Object -Property {$_.Line.Split(':')[-1]}

$GO_Results

output ...

Count Name                      Group                                                                                                                                     
----- ----                      -----                                                                                                                                     
    6 Accordion Cajun Zydeco    {D:\Temp\zzz - Copy\Grouping-List_08-02.log:11:Accordion Cajun Zydeco, D:\Temp\zzz - Copy\Grouping-List_08-09.log:11:Accordion Cajun Zy...
    6 Bawdy Dupe Piano Rocka... {D:\Temp\zzz - Copy\Grouping-List_08-02.log:108:Bawdy Dupe Piano Rockabilly Rowdy, D:\Temp\zzz - Copy\Grouping-List_08-09.log:108:Bawdy...
    6 Bawdy Piano Rockabilly... {D:\Temp\zzz - Copy\Grouping-List_08-02.log:138:Bawdy Piano Rockabilly Rowdy, D:\Temp\zzz - Copy\Grouping-List_08-09.log:138:Bawdy Pian...
    6 Dupe Piano Rockabilly ... {D:\Temp\zzz - Copy\Grouping-List_08-02.log:948:Dupe Piano Rockabilly Rowdy, D:\Temp\zzz - Copy\Grouping-List_08-09.log:948:Dupe Piano ...
    6 Instrumental Piano Roc... {D:\Temp\zzz - Copy\Grouping-List_08-02.log:1563:Instrumental Piano Rockabilly Rowdy, D:\Temp\zzz - Copy\Grouping-List_08-09.log:1563:I...
    6 Piano Rockabilly Rowdy    {D:\Temp\zzz - Copy\Grouping-List_08-02.log:1781:Piano Rockabilly Rowdy, D:\Temp\zzz - Copy\Grouping-List_08-09.log:1781:Piano Rockabil...

note that the .Group contains an array of lines from the matches sent out by the S-S call. you can send that to your output file.

Here is my take at solving this problem, very similar to Lee_Dailey's nice answer but with a foreach loop. I would recommend investing some time into researching the multi-threading options available on PowerShell in case you need to increase the performance of the script, you can look specifically at the ThreadJob module by Microsoft which is really easy to use or if you can't install modules due to some work policy, you can use Runspace.

It is worth adding that you can use the -List switch on Select-String, this way the performance of the script would be increased even more:

-List
Only the first instance of matching text is returned from each input file. This is the most efficient way to retrieve a list of files that have contents matching the regular expression.

$map = @{
    abc123 = 'C:\out_abc123.txt'
    abc124 = 'C:\out_abc124.txt'
    abc125 = 'C:\out_abc125.txt'
}

$pattern = $map.Keys -join '|'

$match = foreach($file in Get-ChildItem *.txt)
{
    Select-String -LiteralPath $file.FullName -Pattern $pattern
}

$match | Group-Object { $_.Matches.Value } | ForEach-Object {
    $_.Group | Select-Object Path, LineNumber, Line | Out-File $map[$_.Name]
}

To compliment the answers @Santiago Squarzon and Lee_Dailey, I think you were actually on the good way yourself knowing that the Group-Object cmdlet is pretty expensive especially in memory usage as it chokes the PowerShell pipeline causing all the search results to be piled up in memory.

Besides, the Select-String cmdlet supports multiple (-SimpleMatch) patterns, where concatenating the search patters with an | (-join '|') will force you to use an (escaped) regular expression.

To continue on your approach:
^{(note that in the example, I am using my own settings to search through my script files)}

$ProgressFile = '.\ResultsCount.txt'
$SearchRoot = '..\'
$Filter = '*.ps1'
$Searches = @{
    'Null'   = '.\Null.txt'
    'Test'   = '.\Test.txt'
    'Object' = '.\Object.txt'
}

$Files = Get-ChildItem -Filter $Filter -Path $SearchRoot -Recurse
$Total = $Files.count

$Searches.Values |ForEach-Object { Set-Content -LiteralPath $_ -Value '' }

$i = 0
ForEach ($File in $Files) {
    Get-Content -LiteralPath $File.FullName |
        Select-String @($Searches.Keys) -AllMatches |ForEach-Object {
            $Value = '{0}:{1}:{2}' -f $File.FullName, $_.LineNumber, $_
            Add-Content -LiteralPath $Searches[$_.Pattern] -Value $Value
        }
    'Record {0} of {1}' -f ++$i, $Total |Tee-Object -Append .\ProgressFile.txt
}

Explanations

• $Searches = @{ ...
  Maps the search patters with the files, you might also use a PSObject list to specify each search (where you could add columns with e.g. context start/end values, etc.)

• $Searches.Values |ForEach-Object { Set-Content -LiteralPath $_ -Value '' }
  Empties the result files (knowing that they are not part of the main stream you can't use Add-Content)

• $i = 0
  Unfortunately there is no automatic index that initializes with a foreach loop (yet, see: #13772 Automatic variable for the pipeline index)

• Get-Content -LiteralPath $File.FullName
  Load the content once into memory
  Note1: this is a string array.
  Note2: the $Content will be reused each iteration and therefore overwrites the previous one and unloads it from memory

• Select-String @($Searches.Keys) -AllMatches |ForEach-Object {
  Searches the string array using your (multiple) defined patterns. (you might consider to use the -SimpleMatch parameter if your search strings contain special characters.)
  Note: Unfortunately you need to embedded the $Searches.Keys in a array subexpression operator @( ), for details see .Net issue: #56835 Make OrderedDictionaryKeyValueCollection implement IList

• $Value = '{0}:{1}:{2}' -f $File.FullName, $_.LineNumber, $_
  Build an result output string.
  Note: the result of the Select-String does have a (hidden) LineNumber and (matched) Pattern property.

• Add-Content -LiteralPath $Searches[$_.Pattern] -Value $Value
  Add the result string to the specific mapped output file.

• 'Record {0} of {1}' -f $i++, $Total |Tee-Object -Append .\ProgressFile.txt
Tee-Object will write the progress to the standard output (display) and also to the specific file.