YACC

Section: User Commands (1)
Updated: June 3, 1990
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NAME

Yacc - an LALR(1) parser generator

SYNOPSIS

yacc [ -dlrtv ] [ -b prefix ] filename

DESCRIPTION

Yacc reads the grammar specification in the file filename and generates an LR(1) parser for it. The parsers consist of a set of LALR(1) parsing 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.
-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.
-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. (The -r option has not yet been implemented.)
-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 causes a human-readable description of the generated parser to be written to the file y.output.

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

TABLES

There is a program :yyfix that extracts tables from yacc-generated files. The program takes the names of the tables as its command-line arguments. 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 nonzero.

FILES

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 reported on standard error. If there are any LALR(1) conflicts, the number of conflicts is reported on standard error.

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Time: 08:11:38 GMT, January 05, 2023