Flex 2.6.4 Description:
Flex is widely known as the fast lexical analyser and it’s an open source, totally free and multi-platform command-line application implemented in C/C++ and designed from the offset to be used for generating scanners. The scanners generated by the Flex tool, which shouldn’t be confused with a non-GNU free implementation of Lex, are actually programs that can recognize lexical patterns in text, also known as applications that perform pattern-matching on text. Flex has been designed in such a way that it can generate a C source file called "lex.yy.c" which can define the yylex() function. The software is a command-line tool, so you can use it via any terminal emulator.