westes/flex

Health v2 · maintenance only

Flags: no_license

Adoption not part of the score

4039 stars · 572 forks observed · 2026-08-28

What it is AI-extracted, prompt v1, taxonomy v1, 2026-08-29, confidence not recorded

flex is the classic fast lexical analyzer generator that produces C/C++ scanner code from regular-expression pattern specifications. It is the standard successor to lex, widely used in compilers, interpreters, and text-processing tools.

Use cases

• generate a lexer for a programming language in C
• tokenize text with regular expression patterns
• build a scanner for a compiler or interpreter
• replace hand-written string parsing with generated lexing code
• port legacy lex scanner files to modern toolchains

When to choose

• you need a fast, battle-tested lexer generator for C or C++
• you want POSIX lex compatibility
• you are building a compiler front end and need tokenization

When to avoid

• you need a lexer for languages other than C/C++ (consider alternatives like re2c, ANTLR, or language-native lexer libraries)
• you need full parser generation, not just lexing (pair with bison or use a parser generator)
• you want a modern regex engine embedded at runtime rather than generated code

Facets

cli-tool · maturity stable

parser compiler developer-tools parsers developer-tools programming-languages windows cross-platform cli lexer-generator scanner lex c c++ regex linux macos

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