What is the PowerShell equivalent of grep -f for matching patterns from a file?

General Discussions
1

I need to perform the same operation as grep --file=filename using PowerShell grep, where filename contains multiple regular expression patterns (one per line) to match in a text file.

I tried Select-String, but it doesn’t seem to support this option. How can I achieve this functionality in PowerShell?

2

You can replicate grep -f in PowerShell by first reading all the regex patterns from the file and then passing them to Select-String. Something like this works great:

$patterns = Get-Content patterns.txt
Select-String -Path input.txt -Pattern $patterns

Select-String accepts an array of patterns, so each line in patterns.txt is treated as a separate regex. This is the simplest and most direct equivalent of grep -f.

3

PowerShell doesn’t have a direct --file parameter like grep, but you can easily simulate it using a loop or pipeline. For example:

Get-Content patterns.txt | ForEach-Object {
    Select-String -Path input.txt -Pattern $_
}

This will run Select-String for each pattern line in your file. Works especially well when you want to handle matches individually or process results differently per pattern.

4

If you need behavior closer to grep -f with combined results and large pattern files, try:

$patterns = Get-Content patterns.txt | Where-Object { $_ -ne "" }
Get-Content input.txt | Where-Object { $line = $_; $patterns -match $line }

Or, even cleaner:

$patterns = Get-Content patterns.txt
Select-String -Path input.txt -Pattern $patterns -AllMatches

This approach gives you similar output to grep -f and supports regex too.