I'm looking for the PowerShell equivalent to grep --file=filename. If you don't know grep, filename is a text file where each line has a regular expression pattern you want to match.
Maybe I'm missing something obvious, but Select-String doesn't seem to have this option.
The -Pattern parameter in Select-String supports an array of patterns. So the one you're looking for is:
Get-Content .\doc.txt | Select-String -Pattern (Get-Content .\regex.txt)
This searches through the textfile doc.txt by using every regex(one per line) in regex.txt