The Flex lexical analyzer generator is a free software alternative to Lex programming tool.

The description for flex as given by the flex manual:

:flex is a tool for generating scanners: programs which recognized lexical patterns in text. flex reads the given 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 as output a C source file, `lex.yy.c , which defines a routine `yylex() . This file is compiled and linked with the `-lfl library to produce an executable. When the executable is run, it analyzes its input for occurrences of the regular expressions. Whenever it finds one, it executes the corresponding C code...

A similar lexical scanner for C plus plus is flex++.

=External links=