为什么我的 fscanf 总是跳过随机数？

Question

基本上我需要扫描这个文件中的所有值......它几乎可以这样做，但它似乎跳过了随机值，所以它最终没有正确排列。 （这只是我需要为作业做的一部分，所以你不会“放弃答案”，我仍然想自己解决，只需要一点帮助来解决这个问题，因为我卡住了）

https://www.dropbox.com/sh/wterbuyxm76wwrz/AADEtolX68OFrKELI_lxT8_Ra/assignments%20and%20labs/labs/lab5_inputFile.txt?dl=0

代码如下：

int main()
{
    FILE *fp;
    char x[15];
    float ID [1000];
    int i=0, j=0;
    float homework [1000];
    float lab [1000];
    float midterm [1000];
    float Final [1000];
    int count=0;
    char headers[35];
    char y;

    fp= fopen("lab5_inputFile.txt", "r");

    while (fscanf(fp, "%s", x)!=EOF){
        if (count > 728){
            fscanf(fp, "%f", &ID[i]);
            printf("ID : %.1f\n", ID[i]);
            fscanf(fp, "%f", &homework[i]);
            printf("Homework: %.1f\n", homework[i]);
            fscanf(fp, "%f", &lab[i]);
            printf("lab: %.1f\n", lab[i]);
            fscanf(fp, "%f", &midterm[i]);
            printf("Midterm: %.1f\n", midterm[i]);
            fscanf(fp, "%f", &Final[i]);
            printf("Final: %.1f\n", Final[i]);

            i++;
        }
            count ++;

    }
    printf("count = %d\n", count);
    fclose(fp);

我只扫描了最后几个值以使其更易于阅读/调试，在实际代码中我只会跳过标题，在提交之前我还计划更改许多其他内容，就像我可能会使用指针类型和 malloc 而不是数组和其他一堆东西，但我的主要问题是如何解决我在从文件读取到数组时遇到的问题。

提前致谢！

Answer 1

您每次都在跳过第一行x。您应该将其重写为：

char x[100];
/* while (fscanf(fp, "%s", x)!=EOF){ */
fgets(x, 100, fp);  /* Skip first line */
for(; /* ever */; ) {
    if(5 == fscanf(fp, "%f%f%f%f%f", &ID[i], &homework[i], &lab[i], &midterm[i], &Final[i])) {
       printf("ID : %.1f\n", ID[i]);
       printf("Homework: %.1f\n", homework[i]);
       printf("lab: %.1f\n", lab[i]);
       printf("Midterm: %.1f\n", midterm[i]);
       printf("Final: %.1f\n", Final[i]);
       i++;
    } else break;
}

Live example here

Answer 2

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

struct grade
{
    float ID;
    float homework;
    float lab;
    float midterm;
    float final;
};

#define ARRAYSIZE (1000)

int main()
{
    FILE *fp;
    struct grade studentGrades[ARRAYSIZE] = {{0},{0},{0},{0},{0}};
    int i=0;
    int count=0;


    if( NULL == (fp= fopen("lab5_inputFile.txt", "r") ) )
    {
        perror( "fopen for read of lab5_inputFile.txt" );
        exit(1);
    }

    // implied else fopen successful

    char* dummy = malloc(1000*sizeof(char) );
    if( NULL == dummy )
    {
        perror( "malloc for dummy buffer" );
        exit(2);
    }

    // implied else, malloc successful

    char * firstLine = fgets( dummy, sizeof(dummy), fp ); // step past first line of file
    if( NULL == firstLine )
    {
        perror( "fget of first line of file" );
        exit(3);
    }

    // implied else, fgets successful

    free( dummy );

    int itemCount = 0;
    for ( i = 0; i < ARRAYSIZE; i++ )
    {
        itemCount = fscanf(fp, " %f", &studentGrades[i].ID);
        if( EOF == itemCount ) // Note:making assumption that every line, 
                               // after first, is properly formatted
        {
            break; // exit for loop
        }
        if( 1 != itemCount )
        {
            perror("fscanf");
            exit(4);
        }

        // implied else read of ID successful, not end of file

        printf("ID : %.1f\n", studentGrades[i].ID);

        if( 1 != fscanf(fp, " %f", &studentGrades[i].homework) )
        {
            perror( "fscanf of homework");
            exit(5);
        }

        // implied else, read of homework successful

        printf("Homework: %.1f\n", studentGrades[i].homework);

        if( 1 != fscanf(fp, " %f", &studentGrades[i].lab) )
        {
            perror( "fscanf of lab" );
            exit(6);
        }

        // implied else, read of lab successful

        printf("lab: %.1f\n", studentGrades[i].lab);

        if( 1 != fscanf(fp, " %f", &studentGrades[i].midterm) )
        {
            perror( "fscanf of midterm" );
            exit(7);
        }

        // implied else, read of midterm successful

        printf("Midterm: %.1f\n", studentGrades[i].midterm);

        if( 1 != fscanf(fp, " %f", &studentGrades[i].final) )
        {
            perror( "fscanf of final" );
            exit(8);
        }

        // implied else, read of final successful

        printf("Final: %.1f\n", studentGrades[i].final);

        count ++;

    } // end for

    printf("count = %d\n", count);
    fclose(fp);

    return(0);
}

Answer 3

OP 的方法重复读取“一组非空白文本，然后是 5 个数字”。代码应该读取行一次，将其扔掉，然后然后重复读取 5 个数字的组。

读取并折腾第一行，然后使用fgets() 读取直到EOF 的行。使用sscanf() 或strtod() 扫描缓冲区。

char buf[100];
fgets(buf, sizeof buf, fp);  // Read and toss first line
i = 0;

while (fgets(buf, sizeof buf, fp) != NULL) {  // Read until EOF
  if ((i >= 1000) || (sscanf(buf, "%f%f%f%f%f", &ID[i], &homework[i], &lab[i], 
      &midterm[i], &Final[i]) != 5)) {
    fputs("Quit as too many lines or ill formatted\n", stderr);
    break;
  }
  printf("ID : %.1f\n", ID[i]);
  printf("Homework: %.1f\n", homework[i]);
  printf("lab: %.1f\n", lab[i]);
  printf("Midterm: %.1f\n", midterm[i]);
  printf("Final: %.1f\n", Final[i]);
  i++;
}