powershellpowershell-5.1file-monitoring

PowerShell - How to find which paths a given command will execute against?

Problem

I have the command Get-Content -Path $SearchPath -Wait | Select-String -Pattern $SearchTerm which is used to search through debug file(s) for common search terms and display them live to the user.

The $SearchPath & $SearchTerm are configured from user inputs.

I would like to list out the files that will be searched to the user before starting the search.

What I have tried

Attempt #1

Get-ChildItem -Path $SearchPath | Select-Object -ExpandProperty FullName

The problem with this command is that it lists both files & directories. However, only files will be searched in the Get-Content command.

Attempt #2

Since I know that all my files end with .log, I added in a regex check for this to eliminate the directories, like so:

Get-ChildItem -Path $SearchPath | Where-Object { $_.Name -match [regex]'([a-zA-Z0-9])*.log' } | Select-Object -ExpandProperty FullName

The problem with this command is that if $SearchPath is C:\Path\To\The\* it will list only the files in that directory, but not subdirectories. However, the original Get-Content command will check subdirectories.

E.g. It would list C:\Path\To\The\DebugLog.log, but not C:\Path\To\The\SubDir\DebugLog.log, even though Get-Content would search it.

Attempt #3

Okay, so my next thought is that I should add -Recurse to check further directories, like so:

Get-ChildItem -Path $SearchPath -Recurse | Where-Object { $_.Name -match [regex]'([a-zA-Z0-9])*.log' } | Select-Object -ExpandProperty FullName

This solves the first problem, but now if $SearchPath is C:\Path\To\The\DebugLog.log, it will list both C:\Path\To\The\DebugLog.log & C:\Path\To\The\Subfolder\DebugLog.log. But the original Get-Content command will only search C:\Path\To\The\DebugLog.log.

Question

How can I check which files the Get-Content command will search before executing it?

Is Get-ChildItem the right command for this, or is there a better option?

Solution

  • Note that with $SearchPath = 'C:\Path\To\The\*', Get-Content -Path $SearchPath will not search subdirectories. Passing a directory path to Get-Content results in an error.

    Therefore, in order to retrieve all *.log files in the current directory and its immediate subdirectories, use the following:

    $logFilesOfInterest =
  Get-ChildItem -File -Depth 1 -Filter *.log

    You can then pass these files to your Get-Content pipeline, using either of the following approaches:

    # Either: Use the pipeline.
$logFilesOfInterest | Get-Content -Wait | Select-String -Pattern $SearchTerm

# Or: Pass them as *arguments*.
Get-Content -LiteralPath $logFilesOfInterest.FullName -Wait | 
  Select-String -Pattern $SearchTerm

    However, in neither case will -Wait work as you intend:

    To monitor multiple files simultaneously, you'll need to use a form of parallelism, which PowerShell (Core) 7+ can provide via the -Parallel parameter of ForEach-Object:

    # PSv7+ only.

$logFilesOfInterest =
  Get-ChildItem -File -Depth 1 -Filter *.log 

$searchTerm = '.' # Specify your search term here.

$logFilesOfInterest |
  ForEach-Object -ThrottleLimit $logFilesOfInterest.Count -Parallel {
    $_ | Get-Content -Wait | Select-String -Pattern $using:searchTerm 
  }

    In Windows PowerShell, you'll have to use background jobs, which is more cumbersome:

    $logFilesOfInterest =
  Get-ChildItem -File -Depth 1 -Filter *.log 

$searchTerm = '.' # Specify your search term here.

$logFilesOfInterest |
  ForEach-Object -OutVariable jobs {
    Start-Job {
      Get-Content -LiteralPath ($using:_).FullName -Wait | 
        Select-String -Pattern $using:searchTerm |
        ForEach-Object Line
    }
  } |
  Receive-Job -Wait