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flex: The Fast Lexical Analyzer

Table of Contents

1. Overview of Flex
2. Available Downloads
3. Other Resources

Overview of Flex

Flex is a tool for generating scanners. A scanner, sometimes called a tokenizer, is a program which recognizes lexical patterns in text. The flex program reads user-specified input files, or its standard input if no file names are given, for a description of a scanner to generate. The description is in the form of pairs of regular expressions and C code, called rules. Flex generates a C source file named, "lex.yy.c", which defines the function yylex(). The file "lex.yy.c" can be compiled and linked to produce an executable. When the executable is run, it analyzes its input for occurrences of text matching the regular expressions for each rule. Whenever it finds a match, it executes the corresponding C code.

Available Downloads

Below is a list of flex releases, ordered by date, with the most recent release listed first. Releases are available as gzipped or bzipp2ed source tarballs.

February 26, 2008

• flex version 2.5.35 in tar.gz format
• flex version 2.5.35 in tar.bz2 format

December 12, 2007

• flex version 2.5.34 in tar.gz format
• flex version 2.5.34 in tar.bz2 format

February 21, 2006

• flex version 2.5.33 in tar.gz format
• flex version 2.5.33 in tar.bz2 format

March 3, 2003

flex, version 2.5.31. Later releases have made this release obsolete. Only use if you have a particular need to avoid later changes. In particular, bug and security fixes of general interest happened after this release.

June 27, 1997

• flex version 2.5.4a in tar.gz format
• flex version 2.5.4a in tar.bz2 format

Other Resources

• The flex manual contains details of how flex works and how you can use it in your programs and applications.
• the flex-help mailing list is the place to post questions regarding flex usage.
• The flex-announce mailing list provides low-volume news of flex releases.
• The flex SourceForge project page contains links to all flex-related sourceforge-hosted resources.
• The Debian Project Flex Bug Page is often a great place to find patches and information about bug fixes of interest to flex users