Powershell script to modify a .dat file within a zip folder - powershell

Question

I am new to PowerShell and have an issue. I need a PowerShell script to modify the first line of a .dat file within a zip folder. Then the zip folder will be need to be renamed but the file within has to keep the same name.
Any help will be appreciated!
I have the following code. It is reading the latest zip file from one directory and copying it into a new worker2 directory. This is working fine. I am trying to open the file and modify the first line. However the file is blank so the code is not copying into the file.
$today = get-date -Format yyyyMMdd
robocopy "C:\Tcc_Touchpoints\Tcc_Touchpoints\data\fusion\Worker\"
"C:\Tcc_Touchpoints\Tcc_Touchpoints\data\fusion\Worker2\" /s
/maxage:$today
$file = gci C:\Tcc_Touchpoints\Tcc_Touchpoints\data\fusion\Worker2\ | sort
LastWriteTime | select -last 1
$file2 = "C:\Tcc_Touchpoints\Tcc_Touchpoints\data\fusion\Worker2\" + $file
$zipfileName = $file2
$fileToEdit = "Worker.dat"
$path = $zipfileName + '\' + $fileToEdit
$contents = Get-Content $fileToEdit #-path $path
$contents
Add-Type -assembly System.IO.Compression.FileSystem
$zip = [System.IO.Compression.ZipFile]::Open($zipfileName,"Update")
#$zip = [System.IO.Compression.ZipFile]::Open($path,"Update")
$robotsFile = $zip.Entries.Where({$_.name -eq $fileToEdit})
$desiredFile = [System.IO.StreamWriter]($robotsFile).Open()
$desiredFile.BaseStream.SetLength(0)
$desiredFile -replace 'SET PURGE_FUTURE_CHANGES Y','SET
PURGE_FUTURE_CHANGES N'
$desiredFile.Write($contents)
$desiredFile.Flush()
$desiredFile.Close()
# Write the changes and close the zip file
$zip.Dispose()
Write-Host "zip file updated"

Answer 1

Your code is not far off. The following edits a single plain text entry in a ZIP file in-place.
Be sure to use the correct text encoding (i.e. the encoding your Worker.dat actually is in). Not specifying the encoding when working with text files will lead to mangled data at some point, always play it safe there.
using namespace System.Text
using namespace System.IO
using namespace System.IO.Compression
Add-Type -Assembly System.IO.Compression.FileSystem
$fileToEdit = "Worker.dat"
$fileEncoding = [Encoding]::UTF8
$zipFileName = "C:\path\to\your\file.zip"
$zip = [ZipFile]::Open($zipfileName, "Update")
$entry = $zip.Entries.Where({$_.name -eq $fileToEdit}) | Select-Object -First 1
$reader = [StreamReader]::new($entry.Open(), $fileEncoding)
$currentText = $reader.ReadToEnd()
$reader.Dispose()
$newText = $currentText -replace "\}$"," }"
$writer = [StreamWriter]::new($entry.Open(), $fileEncoding)
$writer.Write($newText)
$writer.Dispose()
$zip.Dispose()
This does not set the last modified date of the ZIP entry. You can (propably) do this by setting a new value to the $entry.LastWriteTime property.