如何阅读在C文件中的行由行？ [英] How to read a file line-by-line in C?

问题描述

好吧，我是初学者，当谈到C，如此忍受我。

Okay, I'm a beginner when it comes to C, so bear with me.

下面的问题：我有多达100个IP地址，1每行的文本文件。我需要阅读每一个地址，一个字符串，进入所谓的名单的数组。首先，我假设，排行榜将需要一个二维字符数组。每个IP地址的长度为11个字符，12如果包含'\\ 0'，所以我宣布名单如下：

Here's the problem: I have a text file with up to 100 IP addresses, 1 per line. I need to read each address, as a string, into an array called "list". First, I'm assuming that "list" will need to be a two-dimensional char array. Each IP address is 11 characters in length, 12 if you include '\0', so I declared list as follows:

字符名单[100] [12];

接下来，我尝试使用与fgets来读取数据流：

Next, I attempt to use fgets to read the stream:

  for (i = 0; i < 100; i++)  
  {  
      if (feof(stream))  
          break;  
          for (j = 0; j < 12; j++)  
          fgets(&list[i][j], 12, stream);  
      count++;  
  }

要检查是否字符串被正确读取，我试图将它们输出：

To check to see if the strings were read properly, I attempt to output them:

  for (i = 0; i < 5; i++)  
  {  
      for (j = 0; j < 11; j++)  
          printf("%c", list[i][j]);  
      printf("\n");  
  }

运行程序后，很清楚什么是错的。作为一个初学者，我不知道是什么，但我猜我在读取文件错误。有没有错误。它编译，但在打印两行一个陌生的地址。

After running the program, it's clear something is wrong. Being a beginner, I'm not sure what, but I'm guessing I'm reading the file wrong. There are no errors. It compiles, but prints a strange address on two lines.

任何帮助将是AP preciated。

Any help would be appreciated.

编辑：

我更换了与fgets code这一点：

I replaced the fgets code with this:

for (i = 0; i < 100; i++)
  {
      if (feof(stream))
          break;
      fgets(list[i], 12, stream);
      count++;
  }

现在打印五根弦，但他们是从内存中随机的字符。

It now prints five strings, but they are "random" characters from memory.

推荐答案

首先，内容如下：

      for (j = 0; j < 12; j++)  
      fgets(&list[i][j], 12, stream);

您有一个很大的问题就在这里。这是试图读取的字符串的进入每个连续的字符的阵列中

You have a big problem right here. This is attempting to read a string into each successive character in your array.

总而言之，我认为你正在做这个有很多比它需要的更加复杂。想想你的数组为100个字符串，而与fgets 将在时间的字符串工作。这意味着阅读能是这个样子：

All in all, I think you're making this a lot more complex than it needs to be. Think of your array as 100 strings, and fgets will work with a string at a time. That means reading can look something like this:

for (i=0; i<100 && fgets(list[i], 11, string); i++)
    ;

还有另外一个小的细节处理：与fgets（）通常保持在每行的末尾新行。因此，您可能需要留有余地13个字符（11地址，1新线，1 NUL终止），否则你可能需要将数据读入临时缓冲区，并将其复制到你的列表您已经剥去后才能关闭新线。

There is one other minor detail to deal with: fgets() normally retains the new-line at the end of each line. As such, you may need to leave room for 13 characters (11 for address, 1 for new-line, 1 for NUL terminator), or else you may want to read the data into a temporary buffer, and copy it to your list only after you've stripped off the new-line.

在你目前的code打印的琴弦，你在一次工作一个字符，它可以工作，但不必要的困难。有几个人使用％s的printf的转换，这是罚款本身建议。去用它，但是，你必须简化你的索引了一下。打印第6个地址会是这个样子：

In your current code for printing the strings, you're working one character at a time, which can work, but is unnecessarily difficult. Several people have suggested using the %s printf conversion, which is fine in itself. To go with it, however, you have to simplify your indexing a bit. Printing the first six addresses would look something like this:

for (i=0; i<6; i++)
    printf("%s", list[i]);

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