Flex (lexical analyser generator)
| flex | |
|---|---|
| Developer(s) | Vern Paxson | 
| Initial release | around 1987 | 
| Stable release | 2.6.4
   / May 6, 2017 | 
| Repository | |
| Operating system | Unix-like | 
| Type | Lexical analyzer generator | 
| License | BSD license | 
| Website | github | 
Flex (fast lexical analyzer generator) is a free and open-source software alternative to lex. 
It is a computer program that generates lexical analyzers (also known as "scanners" or "lexers").
It is frequently used as the lex implementation together with Berkeley Yacc parser generator on BSD-derived operating systems (as both lex and yacc are part of POSIX), or together with GNU bison (a version of yacc) in *BSD ports and in Linux distributions.  Unlike Bison, flex is not part of the GNU Project and is not released under the GNU General Public License, although a manual for Flex was produced and published by the Free Software Foundation.