Lex/Yacc
lastmod 2026-11-10created 2015-03-274 edits
Lex and Yacc are a classic pair of Unix tools used to build the front end of compilers and interpreters. Lex generates, as C code, a lexical analyzer that splits an input string into tokens using regular expression rules, and Yacc generates an LALR parser that turns a token sequence into a syntax tree using grammar rules. The two tools work as a pair, and GNU provides compatible implementations, Flex and Bison, which are what is usually used today.