Powershell sed-like opertaion - regex

Question

Consider the following use case:
I have a file in this format:
some_content
major_version=1
minor_version=33
some_other_content
combined_version=1.33
more_content
I want to write a Powershell script that takes Major/Minor as parameter, and increments the corresponding number in the file. So I tried using the -replace operator. This is what I came up with:
# Let's say $Major and $Minor contains the updated numbers (I mean, I incremented one of them by 1, according to the user selection)
$SearchExpr = '(?s)(?<First>.*major\D+)\d+(?<Second>.*minor\D+)\d+(?<Third>.*combined\D+)\d+\.\d+'
$ReplaceExp = "`${First}${Major}`${Second}${Minor}`${Third}${Major}.${Minor}"
$VersionFileContent -replace $SearchExp, $ReplaceExp | Out-File $VersionFile
But it's pretty nasty. The probelm is, that while replacing a string in a text is easy if you know the text, like:
"Girrafe, Zebra, Dog" -replace 'Dog', 'Cat'
Replacing "Whatever is after 'Zebra' " is less..
Ideas?

Answer 1

You could use switch -Regex -File for this quite easily:
$content = switch -Regex -File 'D:\Test\MyFile.txt' {
'^(major|minor)_version=(\d+)' {
'{0}_version={1}' -f $matches[1], ([int]$matches[2] + 1)
}
default { $_ }
}
# for safety, save to a new file
$content | Set-Content -Path 'D:\Test\MyUpdatedFile.txt' -Force
Result:
some_content
major_version=2
minor_version=34
some_other_content
combined_version=1.33
more_content
If you also need to update the combined_version, extend to:
$content = switch -Regex -File 'D:\Test\MyFile.txt' {
'^(major_version)=(\d+)' {
$major = [int]$matches[2] + 1
'{0}={1}' -f $matches[1], $major
}
'^(minor_version)=(\d+)' {
$minor = [int]$matches[2] + 1
'{0}={1}' -f $matches[1], $minor
}
'^(combined_version)=(\d+)' {
'{0}={1}.{2}' -f $matches[1], $major, $minor
}
default { $_ }
}
$content | Set-Content -Path 'D:\Test\MyUpdatedFile.txt' -Force