PowerShell locking File

Question

I am trying to do something very simple in PowerShell.

1. Reading the contents of a file
2. Manipulation some string

3. Saving the modified test back to the file

   function Replace {
     $file = Get-Content C:\Path\File.cs
     $file | foreach {$_ -replace "document.getElementById", "$"} |out-file -filepath C:\Path\File.cs
   }
   

I have tried Set-Content as well.

I always get unauthorized exception. I can see the $file has the file content, error is coming while writing the file.

How can I fix this?

Answer 1

This is likely caused by the Get-Content cmdlet that gets a lock for reading and Out-File that tries to get its lock for writing. Similar question is here: Powershell: how do you read & write I/O within one pipeline?

So the solution would be:

${C:\Path\File.cs} = ${C:\Path\File.cs} | foreach {$_ -replace "document.getElementById", '$'}
${C:\Path\File.cs} = Get-Content C:\Path\File.cs | foreach {$_ -replace  "document.getElementById", '$'}

$content = Get-Content C:\Path\File.cs | foreach {$_ -replace "document.getElementById", '$'}
$content | Set-Content C:\Path\File.cs

Basically you need to buffer the content of the file so that the file can be closed (Get-Content for reading) and after that the buffer should be flushed to the file (Set-Content, during that write lock will be required).

Answer 2

The accepted answer worked for me if I had a single file operation, but when I did multiple Set-Content or Add-Content operations on the same file, I still got the "is being used by another process" error.

In the end I had to write to a temp file, then copy the temp file to the original file:

(Get-Content C:\Path\File.cs) | foreach {$_ -replace "document.getElementById", '$'} | Set-Content C:\Path\File.cs.temp
Copy-Item C:\Path\File.cs.temp C:\Path\File.cs