use powershell to grep through many large files - powershell

Question

I have about 70 CSV files, all 1GB or so in size. On a windows environment I need to grep through them all to find specific lines.
My search file called "input.txt" contains these strings:
CG234242424
CG234234234
CG234234235
In a Linux environment I would do this:
for line in `cat input.txt`; do grep $line *.csv >> output.txt; done;
How would I do this in Powershell?
Background - I'm a Linux guy, This is a once off request by the business users for an audit.

Answer 1

I'd build a regular expression from the strings in the input file, and then use Select-String to check the CSV files for the presence of that pattern:
$re = (Get-Content 'input.txt' | ForEach-Object { [regex]::Escape($_) }) -join '|'
Select-String -Path '*.csv' -Pattern $re -CaseSensitive > 'output.txt'
But since PowerShell produces structured data rather than simple string output, you may want to make use of that structure:
$re = (Get-Content 'input.txt' | ForEach-Object { [regex]::Escape($_) }) -join '|'
Select-String -Path '*.csv' -Pattern $re -CaseSensitive |
Select-Object Filename, LineNumber, Line |
Export-Csv 'output.csv' -NoType
If you must process each string from the input file separately you'd do it like this:
foreach ($line in Get-Content 'input.txt') {
Select-String -Path '*.csv' -Pattern $line -SimpleMatch -CaseSensitive |
Select-Object Filename, LineNumber, Line |
Export-Csv 'output.csv' -NoType -Append
}