The quest is to build a utility that finds some text in every file inside a directory, and print the filename.

Yes, Grep has several parameters to make the recursive grep, and no, you don't always remember how to make such a construct.

So, the one-liner command should be like this:

find . -type f -exec grep -l "your_string_goes_here" {} \; -print | uniq

I put it in a shell called /usr/bin/findx, with this content:

find . -type f -exec grep -l "$@" {} \; -print | uniq

to find some string in a directory, first "cd" to that directory and then run findx:

# findx your_string_goes_gere

Of course you can play with parameters to use a different directory than . , but I found it useful this way.