Years ago, I made a few bug fixes to Tim Charron's "GREP for Windows". These bugs were related to the subdirectory searching option (-S).
This is what Tim Charron's "Grep for Windows" webpage has to say about Grep:
GREP is a well known tool in the unix environment. There are several ports available that I came across for Windows. However, NONE of them allowed me to search through subdirectories (this functionality is easy on unix using the shell's file manipulation tools). I modified GNU grep 2.0 to allow searching of subdirectories.
To search subdirectories, do something like this:
grep -S "searchtext" *.txt
grep -S "searchtext" \personal\files\*.txt
grep -S searchtext C:\*.*
Click here to download the latest version of "Grep for Windows".
** Minor page updates: May 20, 2018.