Question

我正在尝试阅读像这样的文本文件

    1234567890 1234
    9876543210 22

到我的程序中的List结构中。我通过fgets（）读取文件然后使用strtok分隔数字，将它们放入变量然后最终进入List。但是，我发现在执行此操作并打印生成的字符串时，strtok始终将最后一行中的最后一个字符串设为NULL，从而导致分段错误。

fgets(fileOutput,400,filePointer); //Read in a line from the file

inputPlate = strtok(fileOutput," "); // Take the first token, store     into inputPlate

while(fileOutput != NULL)
{
    string = strtok(NULL," ");
    mileage = atoi(string); //Convert from string to integer and store into mileage

    car = initializeCar(mileage,dateNULL,inputPlate);
    avail->next = addList(avail->next,car,0);

    fgets(fileOutput,400,filePointer);
    inputPlate = strtok(fileOutput," ");
}

如何解决此问题？

Answer 1

用fgets()逐行阅读文本文件是好的不检查fgets()的返回值很弱。这导致OP的代码处理超出最后一行。

// Weak code
// fgets(fileOutput,400,filePointer); //Read in a line from the file
// ...
// while(fileOutput != NULL)
// {

最好检查fgets()的结果以确定输入何时完成：

#define LINE_SIZE 400
...
while (fgets(fileOutput, LINE_SIZE, filePointer) != NULL) 
{

然后处理字符串。评估解析成功的一种简单方法是将" %n"附加到sscanf()格式以记录扫描的偏移量。

   char inputPlate[LINE_SIZE];
   int mileage;
   int n = -1;
   sscanf(fileOutput, "%s%d %n", inputPlate, &mileage, &n);
   // Was `n` not changed? Did scanning stop before the string end?
   if (n < 0 || fileOutput[n] != '\0') {
     Handle_Bad_input();
     break;
   } else {
     car = initializeCar(mileage, dateNULL, inputPlate);
     avail->next = addList(avail->next,car,0);
   }
}

Answer 2

您可以使用fscanf()编写一个更简单的解析器：

    FILE *filePointer;
    ... // code not shown for opening the file, initalizing the list...
    char inputPlate[32];
    int mileage;

    while (fscanf(filePointer, "%31s%d", inputPlate, &mileage) == 2) {
        car = initializeCar(mileage, dateNULL, inputPlate);
        avail->next = addList(avail->next, car, 0);
    }

C - 如何将数字的空格分隔文本文件列表读入List

2 个答案: