https://abaj.ai/tags/grep/Recent content in Grep on Aayush Bajaj's Augmenting InfrastructureHugoen© 2026 Aayush BajajFri, 10 Jul 2026 08:15:51 +1000https://abaj.ai/wiki/ccs/linux/regex/Fri, 10 Jul 2026 07:44:46 +1000https://abaj.ai/wiki/ccs/linux/regex/<blockquote> <p>You should not be permitted to write production code if you do not have an journeyman licence in regular expressions or floating point math. &mdash;Rob Pike</p> </blockquote> <p>a regular expression is two things wearing one syntax: a seventy-year-old theorem about finite automata, and the single most-used text-processing tool on unix.<span class="margin-note" data-note="kleene proved the theorem in 1951 in a paper about nerve nets, not text — the grep application came later"> <span class="margin-note-indicator">𐃏</span> </span> this page takes both seriously: the theory tells you exactly what the notation can and cannot express, and the theory&rsquo;s failure modes (backtracking blowups, backreference NP-hardness, the html-parsing folklore) are precisely where practitioners get burned.</p>