将测试路径 output 重定向到文本文件

Question

The txt file is just a bunch of UNC paths, i am trying to get a list of UNC paths from this text file put into another text file after the test-path is validated. it shows the validated paths on screen but the text file does not populate.

$cfgs = Get-Content .\cfgpath.txt
$cfgs | % {
  if (Test-Path $_) { write-host "$_" | Out-File -FilePath c:\temp\1.txt -Append }
}

Answer 1

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 .

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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 ).

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^{[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; eg,
Write-Host hi 6>&1 | % { "[$_]" } Write-Host hi 6>&1 | % { "[$_]" } . Note that the type of the objects output by this redirection is System.Management.Automation.InformationRecord .}

Answer 2

Write-Host only writes to the console. I believe what you want there is Write-Output .

$cfgs = Get-Content .\cfgpath.txt
$cfgs | % {
  if (Test-Path $_) { write-output "$_" | Out-File -FilePath c:\temp\1.txt -Append }
}

Additionally you can just omit the Write-Output and that works too.

$cfgs = Get-Content .\cfgpath.txt
$cfgs | % {
  if (Test-Path $_) { "$_" | Out-File -FilePath c:\temp\1.txt -Append }
}