Following situation:
Really JPBlanc is right. If you want it read as UTF8 then specify that when the file is read.
On a side note, you're losing formatting in here with the [String]+[String] stuff. Not to mention your regex match doesn't work. Check out the regex search changes, and the changes made to the $newMsgs, and the way I'm outputting your data to the file.
# Read data if exists
$data = ""
$startRev = 1;
if (Test-Path test.txt)
{
$data = Get-Content -Path test.txt #-Encoding UTF8
if($data -match "\br([0-9]+)\b"){
$startRev = [int]([regex]::Match($data,"\br([0-9]+)\b")).groups[1].value + 1
}
}
Write-Host Next revision is $startRev
# Define example data to add
$startRev = $startRev + 10
$newMsgs = @"
2014-04-01 - r$startRev`r`n`r`n
Line 1`r`n
Line 2`r`n`r`n
"@
# Write new data back
$newmsgs,$data | Out-File test.txt -Encoding UTF8