破解无线密码

累了闲得无聊，看到一篇很好的文章，以后可能会用到 分享下：

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• 113. 如果使用任何一种”w”模式打开一个已有的文件，文件内容将被删除，以便程序以一个空文件开始操作。

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•  简单的文件压缩程序：

• // reducto.c -- reduces your files by two-thirds!

  #include

  #include     // for exit()

  #include     // for strcpy(), strcat()

  #define LEN 40

   

  int main(int argc, char *argv[])

  {

      FILE  *in, *out;   // declare two FILE pointers

      int ch;

      char name[LEN];    // storage for output filename

      int count = 0;

     

  // check for command-line arguments

      if (argc < 2)      

      {

           fprintf(stderr, "Usage: %s filename\n", argv[0]);

           exit(1);

      }

  // set up input

      if ((in = fopen(argv[1], "r")) == NULL)

      {

          fprintf(stderr, "I couldn't open the file \"%s\"\n",

                  argv[1]);

          exit(2);

      }

  // set up output   

      strncpy(name,argv[1], LEN - 5); // copy filename

      name[LEN - 5] = '\0';

      strcat(name,".red");            // append .red 

      if ((out = fopen(name, "w")) == NULL)

      {                       // open file for writing

          fprintf(stderr,"Can't create output file.\n");

          exit(3);

      }

  // copy data

      while ((ch = getc(in)) != EOF)

          if (count++ % 3 == 0)

              putc(ch, out);  // print every 3rd char

  // clean up   

      if (fclose(in) != 0 || fclose(out) != 0)

          fprintf(stderr,"Error in closing files\n");

     

      return 0;

  }