flex也可以从外部文本文件中读入要解析的文本，用yyrestart(f),可以打开多个文件

并循环打开。

flex也可以从外部文本文件中读入要解析的文本，用yyrestart(f),可以打开多个文件

并循环打开。

另外%option noyywrap，使用默认的flex设置(yywrap()在读完一个输入时调用)

/* Companion source code for "flex & bison", published by O'Reilly

 * Media, ISBN 978-0-596-15597-1

 * Copyright (c) 2009, Taughannock Networks. All rights reserved.

 * See the README file for license conditions and contact info.

 * $Header: /home/johnl/flnb/code/RCS/fb2-2.l,v 2.1 2009/11/08 02:53:18 johnl Exp $

 */

/* fb2-2 read several files */

%option noyywrap

%{

int chars = 0;

int words = 0;

int lines = 0;

int totchars = 0;

int totwords = 0;

int totlines = 0;

%}

%%

[a-zA-Z]+    { words++; chars += strlen(yytext); }

\n        { chars++; lines++; }

.        { chars++; }

%%

main(int argc, char **argv)

{

  int i;

  if(argc < 2) { /* just read stdin */

    yylex();

    printf("%8d%8d%8d\n", lines, words, chars);

    return 0;

  }

  for(i = 1; i < argc; i++) {

    FILE *f = fopen(argv[i], "r");

 

    if(!f) {

      perror(argv[1]);

      return (1);

    }

    yyrestart(f);

    yylex();

    fclose(f);

    printf("%8d%8d%8d %s\n", lines, words, chars, argv[i]);

    totchars += chars; chars = 0;

    totwords += words; words = 0;

    totlines += lines; lines = 0;

  }

  if(argc > 1)

    printf("%8d%8d%8d total\n", totlines, totwords, totchars);

  return 0;

}