Madhav, here's a pleasant, short account of the history of how Ken Thompson, now 78, wrote grep. Here's a nice 2019 interview of Thompson himself talking about grep. It's lovely that grep gets a round of applause :-)

For the slightly braver, there are now command-line tools like ack and ag (and sack and sag) that are recursive and blindingly fast. But grep is still wonderful and probably enough for most purposes.

Best,

Dominik