GNU Project parser generator (yacc replacement)


Compile a bison definition file

$ bison [path/to/file.y]

Compile in debug mode, which causes the resulting parser to write additional information to the standard output
$ bison --debug [path/to/file.y]

Specify the output filename
$ bison --output [path/to/output.c] [path/to/file.y]

Be verbose when compiling
$ bison --verbose


bison [OPTION]... FILE


Bison is a parser generator in the style of yacc(1). It should be upwardly compatible with input files designed for yacc.

Input files should follow the yacc convention of ending in .y. Unlike yacc, the generated files do not have fixed names, but instead use the prefix of the input file. Moreover, if you need to put C++ code in the input file, you can end his name by a C++-like extension (.ypp or .y++), then bison will follow your extension to name the output file (.cpp or .c++). For instance, a grammar description file named parse.yxx would produce the generated parser in a file named, instead of yacc's or old Bison version's

This description of the options that can be given to bison is adapted from the node Invocation in the bison.texi manual, which should be taken as authoritative.

Bison supports both traditional single-letter options and mnemonic long option names. Long option names are indicated with -- instead of -. Abbreviations for option names are allowed as long as they are unique. When a long option takes an argument, like --file-prefix, connect the option name and the argument with =.

Generate a deterministic LR or generalized LR (GLR) parser employing LALR(1), IELR(1), or canonical LR(1) parser tables.

Mandatory arguments to long options are mandatory for short options too. The same is true for optional arguments.

Operation Modes:

-h, --help

display this help and exit

-V, --version

output version information and exit


output directory containing locale-dependent data and exit


output directory containing skeletons and XSLT and exit

-u, --update

apply fixes to the source grammar file and exit

-f, --feature[=FEATURES]

activate miscellaneous features

FEATURES is a list of comma separated words that can include:

caret, diagnostics-show-caret

show errors with carets

fixit, diagnostics-parseable-fixits

show machine-readable fixes


do not generate any file


all of the above


disable all of the above


-W, --warnings[=CATEGORY]

report the warnings falling in CATEGORY


whether to colorize the diagnostics


specify the CSS FILE for colorizer diagnostics

Warning categories include:


S/R conflicts (enabled by default)


R/R conflicts (enabled by default)

counterexamples, cex

generate conflict counterexamples


string aliases not attached to a symbol


obsolete constructs


empty rules without %empty


unset or unused midrule values


useless precedence and associativity


incompatibilities with POSIX Yacc


all other warnings (enabled by default)


all the warnings except 'counterexamples', 'dangling-alias' and 'yacc'


turn off warnings in CATEGORY


turn off all the warnings


treat warnings as errors

WHEN can be one of the following:

always, yes

colorize the output

never, no

don't colorize the output

auto, tty

colorize if the output device is a tty

Tuning the Parser:

-L, --language=LANGUAGE

specify the output programming language

-S, --skeleton=FILE

specify the skeleton to use

-t, --debug

instrument the parser for tracing same as '-Dparse.trace'


enable location support

-D, --define=NAME[=VALUE]

similar to '%define NAME VALUE'

-F, --force-define=NAME[=VALUE]

override '%define NAME VALUE'

-p, --name-prefix=PREFIX

prepend PREFIX to the external symbols deprecated by '-Dapi.prefix={PREFIX}'

-l, --no-lines

don't generate '#line' directives

-k, --token-table

include a table of token names

-y, --yacc

emulate POSIX Yacc

Output Files:

-H, --header=[FILE]

also produce a header file


likewise but cannot specify FILE (for POSIX Yacc)

-r, --report=THINGS

also produce details on the automaton


write report to FILE

-v, --verbose

same as '--report=state'

-b, --file-prefix=PREFIX

specify a PREFIX for output files

-o, --output=FILE

leave output to FILE

-g, --graph[=FILE]

also output a graph of the automaton


also output an HTML report of the automaton

-x, --xml[=FILE]

also output an XML report of the automaton

-M, --file-prefix-map=OLD=NEW replace prefix OLD with NEW when writing file paths

in output files

THINGS is a list of comma separated words that can include:


describe the states


complete the core item sets with their closure


explicitly associate lookahead tokens to items


describe shift/reduce conflicts solving

counterexamples, cex

generate conflict counterexamples


include all the above information


disable the report


Report bugs to <>.
GNU Bison home page: <>.
General help using GNU software: <>.
For complete documentation, run: info bison.


Copyright © 2021 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.


lex(1), flex(1), yacc(1). The full documentation for bison is maintained as a Texinfo manual. If the info and bison programs are properly installed at your site, the command info bison should give you access to the complete manual.


Written by Robert Corbett and Richard Stallman.

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