在空时阻止文件读取c中的垃圾数据 [英] prevent file read rubbish data in c when empty

问题描述

我有问题，当文件为空时它会在屏幕上打印垃圾数据如何避免这种情况



这里是我的代码

i have problem when file is empty it print rubbish data on the screen how to avoid that

here is my code

void openFile()
{
    int i;
    char str[999];
    FILE * file;


    file = fopen("1.txt" , "r");

    if (file)
    {
        while (!feof(file))
        {

            fscanf(file,"%d ",&i);
            printf("%d ", i);

            fscanf(file,"%s ",str);
            printf("%s ",str);

            fscanf(file,"%s",str);
            printf("%s ",str);
        }
        fclose(file);
    }
  }

推荐答案

使用这样的feof非常糟糕 - 因为没有从中读取数据文件在那时，feof将返回false - 因此你打印的值是cr @ p - fscanf，fgets实际上设置了文件结束条件



你更好关闭使用while / break并在每个fscanf之后检查文件结尾 - 例如： -

using feof like that is really bad - since no data has been read from the file at that point, feof will return false - hence the values you are printing are cr@p - fscanf, fgets actually set the end of file condition

you are better off using a while/break and checking for end-of-file after every fscanf - something like :-

while( 1 ) {
  /* read integer */
  fscanf(file,"%d ",&i);
  if ( feof(file) )    /* check for EOF right after fscanf() */
    break;
  printf("%d ", i);

  /* read string */
  fscanf(file,"%d ",&i);
  if ( feof(file) )    /* check for EOF right after fscanf() */
    break;
  printf("%s ",str);

  /* read string */
  fscanf(file,"%d ",&i);
  if ( feof(file) )    /* check for EOF right after fscanf() */
    break;
  printf("%s ",str);

}
fclose(file);

你试图在条件存在之前测试它，这将是永远不会工作您也没有检查 fscanf 的错误退货，因此您的程序将打印任何旧垃圾。你最好只需一次调用 fscanf 来阅读所有字段，例如：

You are trying to test for a condition before it exists, which will never work. You are also not checking for bad returns from fscanf, so your program will print any old rubbish. You would be better off reading all fields in a single call to fscanf, something like:

void openFile()
{
    int i;
    char str1[999];
    char str2[999];
    FILE * file;
 

    file = fopen("1.txt" , "r");
 
    if (file)
    {
        while (fscanf(file,"%d %s %s", &i, str1, str2) == 3)
        {
            printf("%d ", i);
            printf("%s ", str1);
            printf("%s\n",str2);
        }
        fclose(file);
    }
}

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