yacc - yet another compiler-compiler
/usr/ccs/bin/yacc [-dltVv] [-b file_prefix] [ -Q
[y | n] ] [-P parser] [-p sym_prefix] file
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.
The following options are supported:
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), will be changed to file_prefix.tab.c,
file_prefix.tab.h, and file_prefix.output, respec-
-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 association
allows source files other than y.tab.c to access the
-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.
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 may also be
affected by the -p option. However, the -p option does
not affect #define symbols generated by yacc.
Allows you to specify the parser of your choice
instead of /usr/ccs/bin/yaccpar. For example, you can
example% yacc -P ~/myparser parser.y
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 sym-
bol. If YYDEBUG has a non-zero value, then the debug-
ging 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 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 infor-
mation for yacc.
The following operand is required:
file A path name of a file containing instructions for
which a parser is to be created.
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-
extern int yyparse();
/* 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. */
int yyerror(const char *msg)
(void) fprintf(stderr, "%s\n", msg);
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 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
The following exit values are returned:
0 Successful completion.
>0 An error occurred.
state transitions of the generated parser
source code of the generated parser
header file for the generated parser
parser prototype for C programs
See attributes(5) for descriptions of the following attri-
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| Availability | SUNWbtool |
| Interface Stability | Standard |
cc(1B), lex(1), attributes(5), environ(5), standards(5)
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.
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 iden-
Man(1) output converted with