YACC(1) (Extended Software Generation System Utilities) YACC(1)
NAME
yacc - yet another compiler-compiler
SYNOPSIS
yacc [ -vdlt ] grammar
DESCRIPTION
The yacc command converts a context-free grammar into a set
of tables for a simple automaton which executes an LR(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 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 must
be supplied by the user; lex(1) is useful for creating
lexical analyzers usable by yacc.
If the -v flag is given, the file y.output is prepared,
which contains a description of the parsing tables and a
report on conflicts generated by ambiguities in the grammar.
If the -d flag is used, the file y.tab.h is generated with
the #define statements that associate the yacc-assigned
``token codes'' with the user-declared ``token names''.
This allows source files other than y.tab.c to access the
token codes.
If the -l flag is given, the code produced in y.tab.c will
not contain any #line constructs. This should only be used
after the grammar and the associated actions are fully
debugged.
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. However, when yacc's
-t option is used, this debugging code will be compiled by
default. Independent of whether the -t option was used, the
runtime debugging code is under the control of YYDEBUG, a
Page 1 May 1989
YACC(1) (Extended Software Generation System Utilities) YACC(1)
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.
FILES
y.output
y.tab.c
y.tab.h defines for token names
yacc.tmp,
yacc.debug, yacc.acts temporary files
/usr/lib/yaccpar parser prototype for C programs
SEE ALSO
lex(1).
Programmer's 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 is also
reported.
CAVEAT
Because file names are fixed, at most one yacc process can
be active in a given directory at a given time.
Page 2 May 1989