检测的feof文件的假结束 [英] feof detecting false end of file

问题描述

我问这个早了不同的问题，但我是大错特错了那么我创建了一个新的问题，因为我要问一个完全不同的问题。这个问题

I asked a different question about this earlier, but I was way off base about the problem so I've created a new question as I'm asking an entirely different question.

我有一个函数读取一个文本文件中的给定线（由交流变频给出）。它执行的行的读出，然后检查，如果这是在该文件中的最后一行。如果因此增加的值。

I have a function that reads a given line in a text file (given by ac variable). It performs the read of the line and then checks if that was the last line in the file. If so it increments a value.

的问题是，它的增加的值，即使它不是文件的实际结束。我想我使用的feof错了，但我已经没有运气得到它的工作：

The problem is that it's incremented the value even when it's not the actual end of the file. I think I'm using feof wrong but I've had no luck getting it to work:

int readIn(TinCan* inCan, int toggle)
  {
  int ii, isFinished = 0;
  char fullName[20];
  sprintf(fullName, "Label_%d.txt", inCan->pid);

  FILE* fp; 
    fp = fopen(fullName, "r");

    if(fp==NULL) 
      {
      printf("Error: could not open %s\n", fullName);
      }

    else
      {
      for (ii=0; ii < ((inCan->ac)-1); ii++)
        {
        fscanf(fp, "%*d %*d %*d\n"); /*move through lines without scanning*/
        }
      fscanf(fp,"%d %d %d", &inCan->ac, &inCan->state, &inCan->time);
      }

    if (feof(fp) && (toggle == 1)) 
      {
      printf("File ended"); 
      writeLog(inCan);
      isFinished = 1;
      terminated++;
      }

  fclose(fp);
  return finished;
  }

根据要求

样本数据，这是一个文本文件，我可以用：

Sample data as requested, this is a text file I may use:

1 1 30
2 2 5
3 1 1

FSCANF正确分配值。在第二行，的feof返回true，终止递增。的feof再次为第3行返回true，增量结束了第二次。

fscanf correctly assigns the values. On the second line, feof returns true and terminated is incremented. feof returns true again for the 3rd line and increments terminated a second time.

推荐答案

的feof（）不如果文件已经结束检测。它可以检测，如果最后读取错误是由于已经结束的文件。

feof() does not detect if the file has ended. It detects if the last read error was due to the file having ended.

的 的feof（）只是读取失败后会发生。的

feof() only happens after a failed read.

所以，首先读取数据和检查返回值。如果读取失败使用的feof（），以确保它失败，因为档案结尾达到（其他原因读取失败是某种（网络错误下来，坏扇区，起火打印机，...），检测与 FERROR（））。

So, first read data and check the return value. If the read failed use feof() to make sure it failed because the END-OF-FILE was reached (other reasons for the read to fail are error of some kind (network down, bad sector, printer on fire, ...), detectable with ferror()).

这篇关于检测的feof文件的假结束的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！