c语言中如何使用fscanf从文件中读取数据

Question

我想用“fscanf”导入数字（总共 40000 个，space 分隔）（格式：2.000000000000000000e+02）并将其放入一维数组中。我尝试了很多东西，但我得到的数字很奇怪。

到目前为止我得到的：

int main() {
        FILE* pixel = fopen("/Users/xy/sample.txt", "r");
        float arr[40000];
        fscanf(pixel,"%f", arr);
   
        for(int i = 0; i<40000; i++)
            printf("%f", arr[i]);
}

我希望有人能帮助我，我是初学者 ;-) 非常感谢！！

Answer 1

你需要循环调用fscanf()。你只读了一个数字。

int main() {
    FILE* pixel = fopen("/Users/xy/sample.txt", "r");
    if (!pixel) {
        printf("Unable to open file\n");
        exit(1);
    }

    float arr[40000];
    for (int i = 0; i < 40000; i++) {
        fscanf(pixel, "%f", &arr[i]);
    }

    for(int i = 0; i<40000; i++) {
        printf("%f", arr[i]);
    }
    printf("\n");
}

Answer 2

而不是：

fscanf(pixel,"%f", arr);

与此完全等价且只读取一个值：

fscanf(pixel,"%f", &arr[0]);

你想要这个：

for(int i = 0; i<40000; i++)
   fscanf(pixel,"%f", &arr[i]);

完整代码：

#include <stdio.h>
#include <stdlib.h>

int main() {
  FILE* pixel = fopen("/Users/xy/sample.txt", "r");
  if (pixel == NULL)   // check if file could be opened
  {
    printf("Can't open file");
    exit(1);
  }

  float arr[40000];
  int nbofvaluesread = 0;

  for(int i = 0; i < 40000; i++)  // read 40000 values
  {
     if (fscanf(pixel,"%f", &arr[i]) != 1)
       break;     // stop loop if nothing could be read or because there
                  // are less than 40000 values in the file, or some 
                  // other rubbish is in the file
     nbofvaluesread++;
  } 
  
  for(int i = 0; i < nbofvaluesread ; i++)
     printf("%f", arr[i]);

  fclose(pixel);  // don't forget to close the file
}

免责声明：这是未经测试的代码，但它应该让您了解自己做错了什么。

c语言中如何使用fscanf从文件中读取数据

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