redirecting test-path output to text file

by

To complement Zam’s helpful answer with background information:

  • Write-Host writes to the host[1] (typically, the console aka terminal), which bypasses PowerShell’s success output stream and therefore sends nothing trough the pipeline.

    • See the bottom section of this answer for when Write-Host is appropriate; in short: you should generally only use it for display-only output.

  • Write-Output is the appropriate cmdlet for producing data output, but it is rarely necessary, because you can rely on PowerShell’s convenient implicit output behavior, as shown in Steven’s answer and explained in this answer.

Also, your command will perform much better if you simply pipe the % (ForEach-Object) command’s output as a whole to a single Out-File call, rather than calling Out-File -Append for each input path.

Instead of using % with conditional explicit output, you can more elegantly implement your command with the Where-Object cmdlet:

Get-Content .\cfgpath.txt |
  Where-Object { Test-Path $_ } |
    Out-File -FilePath c:\temp\1.txt

Also note that for saving strings to a file it is more efficient to use Set-Content instead of
Out-File, though note that in Windows PowerShell the default output character encoding differs (no longer a concern in PowerShell [Core] 6+, which consistently defaults to BOM-less UTF-8); see this answer for when to choose which cmdlet.

By contrast, Out-File and > (its effective alias) use PowerShell’s formatting system to write for-display representations of any non-string input objects to the output file, the same way that output renders to the display by default.
In other words: To save objects to a file in a way that is suitable for later programmatic processing, you need to use a structured file format, such as CSV (Export-Csv) or JSON (ConvertTo-Json, combined with Set-Content).

[1] In PowerShell 5.0 and higher, Write-Host now writes to a new stream, the information stream (number 6), which by default prints to the host. See about_Redirection.
Therefore, a 6> redirection now technically does allow you to send Write-Host output through the pipeline (though doing so is not a good idea) or capture / redirect it; e.g.,
Write-Host hi 6>&1 | % { "[$_]" }. Note that the type of the objects output by this redirection is System.Management.Automation.InformationRecord.

More Related Contents:

  1. Output file doesn’t match Write-Host
  2. Use PowerShell to run virus scan on multiple servers
  3. How do I pass named parameters with Invoke-Command?
  4. What’s the difference between “Write-Host”, “Write-Output”, or “[console]::WriteLine”?
  5. How do you run a SQL Server query from PowerShell?
  6. How to create permanent PowerShell Aliases
  7. How to replace multiple strings in a file using PowerShell
  8. Merging multiple CSV files into one using PowerShell
  9. Maximize window and bring it in front with powershell
  10. Why and how are these two $null values different?
  11. How do I run a PowerShell script when the computer starts?
  12. A better way to check if a path exists or not in PowerShell [closed]
  13. Create directory if it does not exist
  14. PowerShell – get process ID of called application
  15. Delete all files and folders but exclude a subfolder
  16. Can the following Nested foreach loop be simplified in PowerShell?
  17. Add Write-Progress to Get-Job/Wait-Job
  18. Powershell with exchange– How do I append all verbose output to a file
  19. How to handle command-line arguments in PowerShell
  20. How to send email with PowerShell
  21. How to split string by string in Powershell
  22. Powershell: Colon in commandlet parameters
  23. Passing PowerShell variables into a script block
  24. Why is $false -eq “” true?
  25. Using Powershell environmental variables as strings when outputting files
  26. Check if a file exists or not in Windows PowerShell?
  27. Variable scoping in PowerShell
  28. PowerShell launch script in new instance
  29. Read a Csv file with powershell and capture corresponding data
  30. How to return specific data type from PowerShell function i.e. DataTable

Leave a Comment