yacc(1) yacc(1) NAME yacc - yet another compiler-compiler SYNOPSIS yacc [-vVdlt] [-Q[y|n]] [-p sym_prefix] [-b file_prefix] [-P parser] file DESCRIPTION The yacc command converts a context-free grammar into a set of tables for a simple automaton that executes an LALR(1) parsing algorithm. The grammar may be ambiguous; specified precedence rules are used to break ambiguities. yacc processes supplementary code set characters in program comments and strings, and single-byte supplementary code set characters in tokens, according to the locale specified in the LC_CTYPE environment variable [see LANG on environ(5)]. The output file, y.tab.c, must be compiled by the C compiler to produce a program yyparse. This program must be loaded with the lexical analyzer program, yylex, as well as main and yyerror, an error handling routine. These routines may be supplied by the user; the lex(1) command is useful for creating lexical analyzers usable by yacc. A simple main and yyerror are available in liby. The yyerror routine in liby.a has the following signature: int yyerror(const char *). If a user wishes to have a yyerror with a different signature, they must define the symbol __my_yyerror at the top of their .y file. -v Prepares the file y.output, which contains a description of the parsing tables and a report on conflicts generated by ambiguities in the grammar. -b file_prefix Use file_prefix instead of y as the prefix for all output filenames. -p sym_prefix Use sym_prefix instead of yy as the prefix for all external names produced by yacc. For X/Open compliance, when the environment variable _XPG is set, then the -p option will work as described in the previous sentence. If the environment variable _XPG is not set, then the -p option will work as described below in the -P option. -P file Location of the common parser; the code contained here is emitted verbatim by yacc in the generated code. This provides compatibility with the old -p flag in AT&T yacc. -d Generates the file y.tab.h with the #define statements that associate the yacc-assigned ``token codes'' with the user- declared ``token names.'' This association allows source files other than y.tab.c to access the token codes. -l Specifies that the code produced in y.tab.c will not contain any #line constructs. This option should only be used after the grammar and the associated actions are fully debugged. -Q[y|n] The -Qy option puts the version stamping information in y.tab.c. This allows you to know what version of yacc built the file. The -Qn option (the default) writes no version information. -t Compiles runtime debugging code by default. Runtime debugging code is always generated in y.tab.c under conditional compilation control. By default, this code is not included when y.tab.c is compiled. Whether or not the -t option is used, the runtime debugging code is under the control of YYDEBUG, a preprocessor symbol. If YYDEBUG has a non-zero value, then the debugging code is included. If its value is zero, then the code will not be included. The size and execution time of a program produced without the runtime debugging code will be smaller and slightly faster. -V Prints on the standard error output the version information for yacc. FILES y.output y.tab.c y.tab.h defines for token names yacc.tmp, yacc.debug, yacc.acts temporary files; these names are used only if the TMPDIR environment variable is not set. If TMPDIR is set, then these temporary files are stored in that directory, using unique names. /usr/lib/yaccpar parser prototype for C programs SEE ALSO lex(1) DIAGNOSTICS The number of reduce-reduce and shift-reduce conflicts is reported on the standard error output; a more detailed report is found in the y.output file. Similarly, if some rules are not reachable from the start symbol, this instance is also reported. NOTES Because file names are fixed, at most one yacc process can be active in a given directory at a given time. Page 2