yacc(1) User Commands yacc(1)NAMEyacc - yet another compiler-compiler
SYNOPSISyacc [-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 ana‐
lyzer program, yylex(), as well as main() and yyerror(), an error han‐
dling routine. These routines must be supplied by the user. The lex(1)
command is useful for creating lexical analyzers usable by yacc.
OPTIONS
The following options are supported:
-b file_prefix Uses file_prefix instead of y as the prefix for all
output files. The code file y.tab.c, the header file
y.tab.h (created when -d is specified), and the
description file y.output (created when -v is speci‐
fied), is changed to file_prefix.tab.c, file_pre‐
fix.tab.h, and file_prefix.output, respectively.
-d Generates the file y.tab.h with the #define state‐
ments that associate the yacc user-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 does not
contain any #line constructs. 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 prefix for all
external names produced by yacc. The names affected
include the functions yyparse(), yylex() and yyer‐
ror(), and the variables yylval, yychar and yydebug.
(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 be
affected 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 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
0, then the code is not included. The size and execu‐
tion time of a program produced without the runtime
debugging code is smaller and slightly faster.
-v Prepares the file y.output, which contains a descrip‐
tion of the parsing tables and a report on conflicts
generated by ambiguities in the grammar.
-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 programmer. These library func‐
tions are similar to the following code:
#include <locale.h>
int main(void)
{
extern int yyparse();
setlocale(LC_ALL, "");
/* If the following parser is one created by lex, the
application must be careful to ensure that LC_CTYPE
and LC_COLLATE are set to the POSIX locale. */
(void) yyparse();
return (0);
}
#include <stdio.h>
int yyerror(const char *msg)
{
(void) fprintf(stderr, "%s\n", msg);
return (0);
}
ENVIRONMENT VARIABLES
See environ(5) for descriptions of the following environment variables
that affect the execution of yacc: LANG, LC_ALL, LC_CTYPE, LC_MESSAGES,
and NLSPATH.
yacc can handle characters from EUC primary and supplementary 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 parser
yacc.acts temporary file
yacc.debug temporary file
yacc.tmp temporary file
yaccpar parser prototype for C programs
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Availability │developer/object-file │
├─────────────────────────────┼─────────────────────────────┤
│Interface Stability │Committed │
├─────────────────────────────┼─────────────────────────────┤
│Standard │See standards(5). │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOlex(1), attributes(5), environ(5), standards(5)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.
Users are encouraged to avoid using $ as part of any identifier name.
SunOS 5.11 24 Aug 2009 yacc(1)
