User Commands yacc(1)
NAME
yacc - yet another compiler-compiler
SYNOPSIS
yacc [-dltVv] [-b file_prefix] [-Q [y | n]]
[-P parser] [-p sym_prefix] 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 can be ambiguous. Specified precedence rules are used to break ambiguities. The output file, y.tab.c, must be compiled by the C compiler to produce a function yyparse(). This program must be loaded with the lexical analyzer program, yylex(), as well asmain() and yyerror(), an error handling routine. These rou-
tines must be supplied by the user. The lex(1) command isuseful for creating lexical analyzers usable by yacc.
OPTIONS The following options are supported:-b file_prefix Uses file_prefix instead of y as the pre-
fix for all output files. The code file y.tab.c, the header file y.tab.h (createdwhen -d is specified), and the description
file y.output (created when -v is speci-
fied), is changed to file_prefix.tab.c,
file_prefix.tab.h, and file_prefix.output,
respectively.-d Generates the file y.tab.h with the
#define statements that associate the yacc
user-assigned "token codes" with the
user-declared "token names". This associa-
tion allows source files other than y.tab.c to access the token codes.-l Specifies that the code produced in
y.tab.c does not contain any #line con-
structs. This option should only be used after the grammar and the associated actions are fully debugged.-p sym_prefix Uses sym_prefix instead of yy as the pre-
fix for all external names produced bySunOS 5.11 Last change: 24 Aug 2009 1
User Commands yacc(1)
yacc. The names affected include the func-
tions yyparse(), yylex() and yyerror(),and the variables yylval, yychar and yyde-
bug. (In the remainder of this section, the six symbols cited are referenced using their default names only as a notational convenience.) Local names can also beaffected by the -p option. However, the -p
option does not affect #define symbols
generated by yacc.
-P parser Allows you to specify the parser of your
choice instead of/usr/share/lib/ccs/yaccpar. For example,
you can specify:example% yacc -P ~/myparser parser.y
-Q[y|n] The -Qy option puts the version stamping
information in y.tab.c. This allows you toknow 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 con-
trol of YYDEBUG , a preprocessor symbol.If YYDEBUG has a non-zero value, then the
debugging code is included. If its value is 0, then the code is not included. Thesize and execution time of a program pro-
duced without the runtime debugging code is smaller and slightly faster.-v Prepares the file y.output, which contains
a description of the parsing tables and areport on conflicts generated by ambigui-
ties in the grammar.SunOS 5.11 Last change: 24 Aug 2009 2
User Commands yacc(1)
-V Prints on the standard error output the
version information for yacc.
OPERANDS The following operand is required: file A path name of a file containing instructions for which a parser is to be created.EXAMPLES
Example 1 Accessing the yacc Library
Access to the yacc library is obtained with library search
operands to cc. To use the yacc library main:
example% cc y.tab.c -ly
Both the lex library and the yacc library contain main. To
access the yacc main:
example% cc y.tab.c lex.yy.c -ly -ll
This ensures that the yacc library is searched first, so
that its main is used.The historical yacc libraries have contained two simple
functions that are normally coded by the application pro-
grammer. These library functions are similar to the follow-
ing code:#include
int main(void) { extern int yyparse();setlocale(LC_ALL, "");
/* If the following parser is one created by lex, theSunOS 5.11 Last change: 24 Aug 2009 3
User Commands yacc(1)
application must be careful to ensure that LC_CTYPE
and LC_COLLATE are set to the POSIX locale. */
(void) yyparse(); return (0); }#include
int yyerror(const char *msg) {(void) fprintf(stderr, "%s\n", msg);
return (0); } ENVIRONMENT VARIABLES See environ(5) for descriptions of the following environmentvariables that affect the execution of yacc: LANG, LC_ALL,
LC_CTYPE, LC_MESSAGES, and NLSPATH.
yacc can handle characters from EUC primary and supplemen-
tary codesets as one-token symbols. EUC codes can only be
single character quoted terminal symbols. yacc expects
yylex() to return a wide character (wchar_t) value for these
one-token symbols.
EXIT STATUS The following exit values are returned: 0 Successful completion. >0 An error occurred. FILES y.output state transitions of the generated parser y.tab.c source code of the generated parser y.tab.h header file for the generated parseryacc.acts temporary file
yacc.debug temporary file
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User Commands yacc(1)
yacc.tmp temporary file
yaccpar parser prototype for C programs
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | developer/object-file |
|_____________________________|_____________________________|
| Interface Stability | Committed ||_____________________________|_____________________________|
| Standard | See standards(5). ||_____________________________|_____________________________|
SEE ALSO
lex(1), attributes(5), environ(5), standards(5) DIAGNOSTICSThe 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. NOTESBecause file names are fixed, at most one yacc process can
be active in a given directory at a given time.Users are encouraged to avoid using $ as part of any iden-
tifier name.SunOS 5.11 Last change: 24 Aug 2009 5