NAME
yacc - yet another compiler-compiler
SYNOPSIS
/usr/ccs/bin/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 may 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 as
main() and yyerror(), an error handling routine. These rou-
tines 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
Use 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
specified), will be changed to file_prefix.tab.c,
file_prefix.tab.h, and file_prefix.output, respec-
tively.
-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 will
not contain any #line constructs. This option
should only be used after the grammar and the
associated actions are fully debugged.
-P parser Allows you to specify the parser of your choice
instead of /usr/ccs/bin/yaccpar. For example, you
can specify:
example% yacc -P ~/myparser parser.y
-p sym_prefix
Use sym_prefix instead of yy as the prefix for all
external names produced by yacc . The names
affected include the functions yyparse(), yylex()
and yyerror(), 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 may also be affected by the -p option;
however, the -p option does not affect #define
symbols generated by yacc .
-Q[y|n] The -Qy option puts the version stamping informa-
tion in y.tab.c. This allows you to know what ver-
sion of yacc built the file. The -Qn option (the
default) writes no version information.
-t Compiles runtime debugging code by default. Run-
time 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 com-
piled. 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 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 .
-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.
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: Using The yacc Command
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 <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 : LC_CTYPE,
LC_MESSAGES, and NLSPATH.
yacc can handle characters from EUC primary and supplemen-
tary codesets as one-token symbols. EUC codes may 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 attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWbtool |
|_____________________________|_____________________________|
SEE ALSO
cc(1B), lex(1), attributes(5), environ(5)
Programming Utilities Guide
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.
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