I didn't know that Ken Thompson was one of the first programmers to implement regular expressions (in the QED editor for CTSS). That explains why there is so mu

I didn't know that Ken Thompson was one of the first programmers to implement regular expressions (in the QED editor for CTSS). That explains why there is so much use of regular expressions and pattern matching in Unix! Now it is quite common to see regular expressions in many tools and programming languages, but when I started using Unix in 1983 I was surprised to see so many uses of regular expressions.