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YACC(1)                 NetBSD General Commands Manual                 YACC(1)


NAME

     yacc -- an LALR(1) parser generator


SYNOPSIS

     yacc [-dgilPrtVv] [-b prefix] [-o outputfile] [-p symbol_prefix] filename


DESCRIPTION

     yacc reads the grammar specification in the file filename and generates
     an LALR(1) parser for it.  The parsers consist of a set of LALR(1) pars-
     ing tables and a driver routine written in the C programming language.
     yacc normally writes the parse tables and the driver routine to the file
     y.tab.c.

     The following options are available:

     -b prefix     The -b option changes the prefix prepended to the output
                   file names to the string denoted by prefix.  The default
                   prefix is the character y.

     -d            The -d option causes the header file y.tab.h to be written.
                   It contains #define's for the token identifiers.

     -g            The -g option causes a graphical description of the gener-
                   ated LALR(1) parser to be written to the file y.dot in
                   graphviz format, ready to be processed by dot(1).

     -i            The -i option causes a supplementary header file y.tab.i to
                   be written.  It contains extern declarations and supplemen-
                   tary #define's as needed to map the conventional yacc yy-
                   prefixed names to whatever the -p option may specify.  The
                   code file, e.g., y.tab.c is modified to #include this file
                   as well as the y.tab.h file, enforcing consistent usage of
                   the symbols defined in those files.  The supplementary
                   header file makes it simpler to separate compilation of
                   lex- and yacc-files.

     -l            If the -l option is not specified, yacc will insert #line
                   directives in the generated code.  The #line directives let
                   the C compiler relate errors in the generated code to the
                   user's original code.  If the -l option is specified, yacc
                   will not insert the #line directives.  #line directives
                   specified by the user will be retained.

     -o outputfile
                   The -o option specifies an explicit output file name should
                   be used instead of the default.

     -P            The -P options instructs yacc to create a reentrant parser,
                   like ``%pure-parser'' does.

     -p symbol_prefix
                   The -p option changes the prefix prepended to yacc-gener-
                   ated symbols to the string denoted by symbol_prefix.  The
                   default prefix is the string yy.

     -r            The -r option causes yacc to produce separate files for
                   code and tables.  The code file is named y.code.c, and the
                   tables file is named y.tab.c.

     -t            The -t option changes the preprocessor directives generated
                   by yacc so that debugging statements will be incorporated
                   in the compiled code.

     -V            The -V option prints the version number to the standard
                   output.

     -v            The -v option causes a human-readable description of the
                   generated parser to be written to the file y.output.


EXTENSIONS

     yacc provides some extensions for compatibility with bison(1) and other
     implementations of yacc:

     %expect number     Tell yacc the expected number of shift/reduce con-
                        flicts.  That makes it only report the number if it
                        differs.
     %expect-rr number  Tell yacc the expected number of reduce/reduce con-
                        flicts.  That makes it only report the number if it
                        differs.  This is (unlike bison(1)) allowable in
                        LALR(1) parsers.
     %lex-param { argument-declaration }
                        By default, the lexer accepts no parameters, e.g.,
                        yylex().  Use this directive to add parameter declara-
                        tions for your customized lexer.
     %parse-param { argument-declaration }
                        By default, the parser accepts no parameters, e.g.,
                        yyparse().  Use this directive to add parameter decla-
                        rations for your customized parser.
     %pure-parser       Most variables (other than yydebug and yynerrs) are
                        allocated on the stack within yyparse(), making the
                        parser reasonably reentrant.


ENVIRONMENT

     The following environment variable is referenced by yacc:

     TMPDIR  If the environment variable TMPDIR is set, the string denoted by
             TMPDIR will be used as the name of the directory where the tempo-
             rary files are created.


TABLES

     The names of the tables generated by this version of yacc are ``yylhs'',
     ``yylen'', ``yydefred'', ``yydgoto'', ``yysindex'', ``yyrindex'',
     ``yygindex'', ``yytable'', and ``yycheck''.  Two additional tables,
     ``yyname'' and ``yyrule'', are created if YYDEBUG is defined and non-
     zero.


FILES

     y.code.c
     y.tab.c
     y.tab.h
     y.output
     /tmp/yacc.aXXXXXX
     /tmp/yacc.tXXXXXX
     /tmp/yacc.uXXXXXX


DIAGNOSTICS

     If there are rules that are never reduced, the number of such rules is
     written to the standard error.  If there are any LALR(1) conflicts, the
     number of conflicts is also written to the standard error.


STANDARDS

     The yacc utility conforms to IEEE Std 1003.2 (``POSIX.2'').

NetBSD 6.0                     September 7, 2011                    NetBSD 6.0