Understanding Grep Algorithms: From Naïve Search to Modern Regex Engines
Introduction grep—the global regular expression printer—has been a staple of Unix‑like systems since the early 1970s. At first glance, it appears to be a simple command‑line utility that searches files for lines matching a pattern. Under the hood, however, grep embodies a rich history of string‑matching algorithms, data‑structure innovations, and practical engineering trade‑offs. Understanding these algorithms not only demystifies why grep behaves the way it does on large data sets, but also equips you to choose the right tool (or tweak the right flags) for a given problem. ...