LEX(1) General Commands Manual LEX(1)NAME
lex - generator of lexical analysis programs
SYNOPSIS
lex [ -tvn ] [ file ... ]
DESCRIPTION
Lex generates programs to be used in simple lexical analysis of text. The input files (standard input default) contain regular expressions
to be searched for and actions written in C to be executed when expressions are found.
A C source program, lex.yy.c is generated. This program, when run, copies unrecognized portions of the input to the output, and executes
the associated C action for each regular expression that is recognized.
The options have the following meanings.
-t Place the result on the standard output instead of in file lex.yy.c.
-v Print a one-line summary of statistics of the generated analyzer.
-n Opposite of -v; -n is default.
EXAMPLES
This program converts upper case to lower, removes blanks at the end of lines, and replaces multiple blanks by single blanks.
%%
[A-Z] putchar(yytext[0]+'a'-'A');
[ ]+$
[ ]+ putchar(' ');
FILES
lex.yy.c
output
/sys/lib/lex/ncform
template
SEE ALSO yacc(1), sed(1)
M. E. Lesk and E. Schmidt, `LEX--Lexical Analyzer Generator', Unix Research System Programmer's Manual, Tenth Edition, Volume 2.
SOURCE
/sys/src/cmd/lex
BUGS
Cannot handle UTF.
The asteroid to kill this dinosaur is still in orbit.
LEX(1)
Check Out this Related Man Page
YACC(1) General Commands Manual YACC(1)NAME
yacc - yet another compiler-compiler
SYNOPSIS
yacc [ option ... ] grammar
DESCRIPTION
Yacc converts a context-free grammar and translation code into a set of tables for an LR(1) parser and translator. 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 This program must be loaded with a lexical analyzer func-
tion, yylex(void) (often generated by lex(1)), with a main(int argc, char *argv[]) program, and with an error handling routine, yyer-
ror(char*).
The options are
-o output Direct output to the specified file instead of y.tab.c.
-Dn Create file y.debug, containing diagnostic messages. To incorporate them in the parser, compile it with preprocessor symbol
yydebug defined. The amount of diagnostic output from the parser is regulated by value n. The value 0 reports errors; 1
reports reductions; higher values (up to 4) include more information about state transitions.
-v Create file y.output, containing a description of the parsing tables and of conflicts arising from ambiguities in the grammar.
-d Create file y.tab.h, containing #define statements that associate yacc-assigned `token codes' with user-declared `token names'.
Include it in source files other than y.tab.c to give access to the token codes.
-s stem Change the prefix of the file names y.tab.c, y.tab.h, y.debug, and y.output to stem.
-S Write a parser that uses Stdio instead of the print routines in libc.
The specification of yacc itself is essentially the same as the UNIX version described in the references mentioned below. Besides the -D
option, the main relevant differences are:
The interface to the C environment is by default through <libc.h> rather than <stdio.h>; the -S option reverses this.
The parser accepts UTF input text (see utf(6)), which has a couple of effects. First, the return value of yylex() no longer fits in
a short; second, the starting value for non-terminals is now 0xE000 rather than 257.
The generated parser can be recursive: actions can call yyparse, for example to implement a sort of #include statement in an inter-
preter.
Finally, some undocumented inner workings of the parser have been changed, which may affect programs that know too much about its
structure.
FILES
y.output
y.tab.c
y.tab.h
y.debug
y.tmp.*
temporary file
y.acts.*
temporary file
/sys/lib/yaccpar
parser prototype
/sys/lib/yaccpars
parser prototype using stdio
SOURCE
/sys/src/cmd/yacc.c
SEE ALSO lex(1)
S. C. Johnson and R. Sethi, ``Yacc: A parser generator'', Unix Research System Programmer's Manual, Tenth Edition, Volume 2
B. W. Kernighan and Rob Pike, The UNIX Programming Environment, Prentice Hall, 1984
BUGS
The parser may not have full information when it writes to y.debug so that the names of the tokens returned by may be missing.
YACC(1)