El proyecto flex en sí viene con un conjunto decente de ejemplos, incluyendo make files y bison files.
https://github.com/westes/flex/releases
Para una excelente introducción al tema, sugiero lex y yacc 2ª edición:
http://oreilly.com/catalog/9781565920002
Por último, vaya aquí para una cartilla rápida :
http://ds9a.nl/lex-yacc/cvs/lex-yacc-howto.html
Editar:
Como se mencionó Bart, otra fuente es: http://oreilly.com/catalog/9780596155988/
Y el siguiente es el archivo de esqueleto que utilizo para iniciar un proyecto Flex. Utiliza gnu getopts para analizar opciones de línea de comando y obtener el nombre del archivo. No reclamo portabilidad o facilidad de uso. :)
/*
* This file is part of flex.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE.
*/
/**************************************************
start of definitions section
***************************************************/
%{
/* A template scanner file to build "scanner.c". */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <getopt.h>
/*#include "parser.h" */
//put your variables here
char FileName[256];
FILE *outfile;
char **myOut;
char inputName[256];
// flags for command line options
static int specificFile_flag = 0;
static int output_flag = 0;
static int help_flag = 0;
%}
%option 8bit outfile="scanner.c"
%option nounput nomain noyywrap
%option warn
%x header
%x fileType
%x final
%%
/************************************************
start of rules section
*************************************************/
/* these flex patterns will eat all input */
. { }
\n { }
%%
/****************************************************
start of code section
*****************************************************/
int main(int argc, char **argv);
int main (argc,argv)
int argc;
char **argv;
{
/****************************************************
The main method drives the program. It gets the filename from the
command line, and opens the initial files to write to. Then it calls the lexer.
After the lexer returns, the main method finishes out the report file,
closes all of the open files, and prints out to the command line to let the
user know it is finished.
****************************************************/
int c;
// the gnu getopt library is used to parse the command line for flags
// afterwards, the final option is assumed to be the input file
while (1) {
static struct option long_options[] = {
/* These options set a flag. */
{"specific-file", no_argument, &specificFile_flag, 1},
{"help", no_argument, &help_flag, 1},
/* These options don't set a flag. We distinguish them by their indices. */
{"debug", no_argument, 0, 'd'},
{"specificFile", no_argument, 0, 's'},
{"useStdOut", no_argument, 0, 'o'},
{0, 0, 0, 0}
};
/* getopt_long stores the option index here. */
int option_index = 0;
c = getopt_long (argc, argv, "dso",
long_options, &option_index);
/* Detect the end of the options. */
if (c == -1)
break;
switch (c) {
case 0:
/* If this option set a flag, do nothing else now. */
if (long_options[option_index].flag != 0)
break;
printf ("option %s", long_options[option_index].name);
if (optarg)
printf (" with arg %s", optarg);
printf ("\n");
break;
case 'd':
break;
case 's':
specificFile_flag = 1;
break;
case 'o':
output_flag = 1;
break;
case '?':
/* getopt_long already printed an error message. */
break;
default:
abort();
}
}
if (help_flag == 1) {
printf("proper syntax is: addressGrabber.exe [OPTIONS]... INFILE OUTFILE\n");
printf("grabs address from prn files\n\n");
printf("Option list: \n");
printf("-s --specific-file changes INFILE from a prn list to a specific prn\n");
printf("-d turns on debug information\n");
printf("-o sets output to stdout\n");
printf("--help print help to screen\n");
printf("\n");
printf("list example: addressGrabber.exe list.csv\n");
printf("prn example: addressGrabber.exe -s 01110500.prn\n\n");
printf("If infile is left out, then stdin is used for input.\n");
printf("If outfile is a filename, then that file is used.\n");
printf("If there is no outfile, then infile-EDIT.tab is used.\n");
printf("There cannot be an outfile without an infile.\n");
return 0;
}
//get the filename off the command line and redirect it to input
//if there is no filename or it is a - then use stdin
if (optind < argc) {
FILE *file;
file = fopen(argv[optind], "rb");
if (!file) {
fprintf(stderr, "Flex could not open %s\n",argv[optind]);
exit(1);
}
yyin = file;
strcpy(inputName, argv[optind]);
}
else {
printf("no input file set, using stdin. Press ctrl-c to quit");
yyin = stdin;
strcpy(inputName, "\b\b\b\b\bagainst stdin");
}
//increment current place in argument list
optind++;
/********************************************
if no input name, then output set to stdout
if no output name then copy input name and add -EDIT.csv
if input name is '-' then output set to stdout
otherwise use output name
*********************************************/
if (optind > argc) {
yyout = stdout;
}
else if (output_flag == 1) {
yyout = stdout;
}
else if (optind < argc){
outfile = fopen(argv[optind], "wb");
if (!outfile) {
fprintf(stderr, "Flex could not open %s\n",FileName);
exit(1);
}
yyout = outfile;
}
else {
strncpy(FileName, argv[optind-1], strlen(argv[optind-1])-4);
FileName[strlen(argv[optind-1])-4] = '\0';
strcat(FileName, "-EDIT.tab");
outfile = fopen(FileName, "wb");
if (!outfile) {
fprintf(stderr, "Flex could not open %s\n",FileName);
exit(1);
}
yyout = outfile;
}
yylex();
if (output_flag == 0) {
fclose(yyout);
}
printf("Flex program finished running file %s\n", inputName);
return 0;
}
Por último, ya que las personas mantienen la comprobación de esto, también tengo una example lexer and parser con makefile en github.
Excelentes recursos. Tal vez incluya http://oreilly.com/catalog/9780596155988/? –
@Bart Kiers He agregado su enlace y la fuente de mi archivo esqueleto flexible. –
Genial, desafortunadamente solo puedo votar una vez :) –