Replace string content between quotes in file - powershell

Question

I have made this loop to iterate some files that I want to replace content in.
The content that I want to replace is a string which can look something like this: foo="1".
What I need your help with is how to find the string (regexp I guess) and update the file with a new value, like 2 for example.
$files = Get-ChildItem -Recurse -Filter "*.config"
foreach ($file in $files)
{
Get-Content $file.FullName
}
Read-Host

Answer 1

From the sample code in the question, I assume you're attempting to update a .NET configuration file (ie. a web.config or app.config file).
Given that these files are really XML files, you may want to treat them as such:
$files = Get-ChildItem -Recurse -Filter "*.config"
foreach ($file in $files)
{
# Create an XmlDocument object from the file
$configXml = [xml](Get-Content $file.FullName)
# Find all the nodes in the document
$xmlNodes = $configXml.SelectNodes('//*')
# Keep track of whether we make changes or not
$changeCount = 0
foreach($node in $xmlNodes)
{
# Check if node has a "foo" attribute
if($node.HasAttribute('foo'))
{
# Set 2 as the value
$node.SetAttribute('foo',2)
$changeCount++
}
}
if($changeCount)
{
# At least one node was updated, save to file
$configXml.Save($file.FullName)
}
}

Answer 2

You can try regex. Ex.
$files = Get-ChildItem -Recurse -Filter "*.config"
$find = 'foo=".*?"'
$replace = 'foo="4"'
foreach ($file in $files)
{
Get-Content $file.FullName |
Foreach-Object { $_ -replace $find, $replace } |
Set-Content $file.Fullname
}
}
Read-Host
Or to only modify files that match:
$files = Get-ChildItem -Recurse -Filter "*.config"
$find = 'foo=".*?"'
$replace = 'foo="4"'
foreach ($file in $files)
{
$content = Get-Content $file.FullName
if(Select-String -InputObject $content -Pattern $find -Quiet) {
$content |
Foreach-Object { $_ -replace $find, $replace } |
Set-Content $file.Fullname
}
}
Read-Host

Answer 3

This should answer your question
$files = Get-ChildItem -Recurse -Filter "*.config"
foreach ($file in $files)
{
$fileContent = Get-Content $file.FullName
$newContent = $fileContent -replace 'foo="1"', 'foo="2"'
Set-Content $file.FullName $newContent
}
Further reading here: Use PowerShell to Replace Text in Strings