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GNU Bison

Introduction to Bison

Bison is a general-purpose parser generator that converts an annotated context-free grammar into a deterministic LR or generalized LR (GLR) parser employing LALR(1) parser tables. As an experimental feature, Bison can also generate IELR(1) or canonical LR(1) parser tables. Once you are proficient with Bison, you can use it to develop a wide range of language parsers, from those used in simple desk calculators to complex programming languages.

Bison is upward compatible with Yacc: all properly-written Yacc grammars ought to work with Bison with no change. Anyone familiar with Yacc should be able to use Bison with little trouble. You need to be fluent in C or C++ programming in order to use Bison. Java is also supported as an experimental feature.

Downloading Bison

Bison can be found on the main GNU ftp server: http://ftp.gnu.org/gnu/bison/ (via HTTP) and ftp://ftp.gnu.org/gnu/bison/ (via FTP). It can also be found on the GNU mirrors; please use a mirror if possible.


Documentation for Bison is available online, as is documentation for most GNU software. You may also find more information about Bison by running info bison or man bison, or by looking at /usr/share/doc/bison/, /usr/local/doc/bison/, or similar directories on your system. A brief summary is available by running bison --help.

Mailing lists

Bison has the following mailing lists:

Announcements about Bison and most other GNU software are made on info-gnu (archive).

Security reports that should not be made immediately public can be sent directly to the maintainer. If there is no response to an urgent issue, you can escalate to the general security mailing list for advice.

Getting involved

Development of Bison, and GNU in general, is a volunteer effort, and you can contribute. For information, please read How to help GNU. If you'd like to get involved, it's a good idea to join the discussion mailing list (see above).

Test releases
Trying the latest test release (when available) is always appreciated. Test releases of Bison can be found at http://alpha.gnu.org/gnu/bison/ (via HTTP) and ftp://alpha.gnu.org/gnu/bison/ (via FTP).
For development sources, issue trackers, and other information, please see the Bison project page at savannah.gnu.org.
Translating Bison
To translate Bison's messages into other languages, please see the Translation Project page for Bison. If you have a new translation of the message strings, or updates to the existing strings, please have the changes made in this repository. Only translations from this site will be incorporated into Bison. For more information, see the Translation Project.
Bison is currently being maintained by Akim Demaille and Paul Eggert. Please use the mailing lists for contact.


Bison is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.


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