PowerShell: Set-Content having issues with "file already in use" - file

Question

I'm working on a PowerShell script that finds all the files with PATTERN within a given DIRECTORY, prints out the relevant lines of the document with the PATTERN highlighted, and then replaces the PATTERN with a provided REPLACE word, then saves the file back. So it actually edits the file.
Except I can't get it to alter the file, because Windows complains about the file already being open. I tried several methods to solve this, but keep running into the issue. Perhaps someone can help:
param(
[string] $pattern = ""
,[string] $replace = ""
,[string] $directory ="."
,[switch] $recurse = $false
,[switch] $caseSensitive = $false)
if($pattern -eq $null -or $pattern -eq "")
{
Write-Error "Please provide a search pattern." ; return
}
if($directory -eq $null -or $directory -eq "")
{
Write-Error "Please provide a directory." ; return
}
if($replace -eq $null -or $replace -eq "")
{
Write-Error "Please provide a string to replace." ; return
}
$regexPattern = $pattern
if($caseSensitive -eq $false) { $regexPattern = "(?i)$regexPattern" }
$regex = New-Object System.Text.RegularExpressions.Regex $regexPattern
function Write-HostAndHighlightPattern([string] $inputText)
{
$index = 0
$length = $inputText.Length
while($index -lt $length)
{
$match = $regex.Match($inputText, $index)
if($match.Success -and $match.Length -gt 0)
{
Write-Host $inputText.SubString($index, $match.Index) -nonewline
Write-Host $match.Value.ToString() -ForegroundColor Red -nonewline
$index = $match.Index + $match.Length
}
else
{
Write-Host $inputText.SubString($index) -nonewline
$index = $inputText.Length
}
}
}
Get-ChildItem $directory -recurse:$recurse |
Select-String -caseSensitive:$caseSensitive -pattern:$pattern |
foreach {
$file = ($directory + $_.FileName)
Write-Host "$($_.FileName)($($_.LineNumber)): " -nonewline
Write-HostAndHighlightPattern $_.Line
%{ Set-Content $file ((Get-Content $file) -replace ([Regex]::Escape("[$pattern]")),"[$replace]")}
Write-Host "`n"
Write-Host "Processed: $($file)"
}
The issue is located within the final block of code, right at the Get-ChildItem call. Of course, some of the code in that block is now a bit mangled due to me trying to fix the problem then stopping, but keep in mind the intent of that part of the script. I want to get the content, replace the words, then save the altered text back to the file I got it from.
Any help at all would be greatly appreciated.

Answer 1

Removed my previous answer, replacing it with this:
Get-ChildItem $directory -recurse:$recurse
foreach {
$file = ($directory + $_.FileName)
(Get-Content $file) | Foreach-object {
$_ -replace ([Regex]::Escape("[$pattern]")),"[$replace]")
} | Set-Content $file
}
Note:
The parentheses around Get-Content to ensure the file is slurped in one go (and therefore closed).
The piping to subsequent commands rather than inlining.
Some of your commands have been removed to ensure it's a simple test.

Answer 2

Just a suggestion but you might try looking at the documentation for the parameters code block. There is a more efficient way to ensure that a parameter is entered if you require it and to throw an error message if the user doesn't.
About_throw: http://technet.microsoft.com/en-us/library/dd819510.aspx
About_functions_advanced_parameters: http://technet.microsoft.com/en-us/library/dd347600.aspx
And then about using Write-Host all the time: http://powershell.com/cs/blogs/donjones/archive/2012/04/06/2012-scripting-games-commentary-stop-using-write-host.aspx

Answer 3

Alright, I finally sat down and just typed everything sequentially in PowerShell, then used that to make my script.
It was actually really simple;
$items = Get-ChildItem $directory -recurse:$recurse
$items |
foreach {
$file = $_.FullName
$content = get-content $file
$newContent = $content -replace $pattern, $replace
Set-Content $file $newcontent
}
Thanks for all your help guys.