使用 fscanf，将文件扫描到 C 中的结构中，但第一个参数已经失败

Question

我有一个文件，我试图在其中将每一行读入 C 中的结构以进一步使用它。

文件如下所示：

Bread,212,2.7,36,6,9.8,0.01,0.01,10,500 
Pasta,347,2.5,64,13,7,0.01,0.01,6,500 
Honey,340,0.01,83,0.01,0.01,0.01,0.01,22.7,425 
Olive-oil,824,92,0.01,0.01,0.01,0.01,13.8,35,500 
White-beans,320,2.7,44,21,18,0.01,0.01,11,400 
Flaxseed-oil,828,92,0.01,0.01,0.01,52,14,100,100 
Cereal,363,6.5,58,13,9.9,0.01,0.01,11,1000 
Hazelnuts,644,61.6,10.5,12,0.01,0.09,7.83,16.74,252

所以我写了一个 for 循环来遍历文件中的行，试图将每个值存储到 struct 的字段中。我尝试打印结构的字段，但第一个参数字符串已经出错了。

正在打印：

scanresult: 1, name:  ■B, kcal: 0.00, omega 3: 0.00, omega 6: 0.00, carb: 0.00, protein: 0.00, fib: 0.00, price: 0.00, weight: 0.00g

Scanres 应该是 10，而不是 1，并且值应该与文件第一行的值匹配。

我试过在格式化字符串的参数前面有或没有空格。我还尝试了编译器警告 -Wall 和 -pedantic。没有发现问题。

还有什么可能导致此问题？

代码如下所示：

#include <stdio.h>

#define MAX_CHAR 100
#define SIZE_OF_SHELF 8

typedef struct {
    char name[MAX_CHAR];
    double kcal, fat, omega_3, omega_6, carb, protein, fib, price, weight;
} Food;

int main(void) {
    int i = 0, scanresult;
    Food Shelf[SIZE_OF_SHELF];
    FILE *fp;

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

    if (! fp) {
        printf("error loading file. bye.\n");
        return 0;
    }

    for (i = 0; !feof(fp); i++) {
        scanres = fscanf(fp, " %[^,],%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf ",
                         Shelf[i].name,
                         &Shelf[i].kcal, &Shelf[i].fat,
                         &Shelf[i].carb, &Shelf[i].protein,
                         &Shelf[i].fib, &Shelf[i].omega_3,
                         &Shelf[i].omega_6, &Shelf[i].price,
                         &Shelf[i].weight);
        
        printf("scanres: %d, name: %s, kcal: %.2f, omega 3: %.2f, omega 6: %.2f, carb: %.2f, protein: %.2f, fib: %.2f, price: %.2f, weight: %.2fg\n",
               scanres, Shelf[i].name, Shelf[i].kcal,
               Shelf[i].omega_3, Shelf[i].omega_6, Shelf[i].carb, 
               Shelf[i].protein, Shelf[i].fib, Shelf[i].price,
               Shelf[i].weight);
    }
    return 0;
}

如果有人发现我做错了什么，请告诉我。

Answer 1

检查文件的前三个字符是否有字节顺序标记 (BOM)。您可以使用 hexdump（或任何二进制编辑器）来检查它。

文件 BOM:

00000000  ef bb bf 42 72 65 61 64  2c 32 31 32 2c 32 2e 37  |...Bread,212,2.7|
00000010  2c 33 36 2c 36 2c 39 2e  38 2c 30 2e 30 31 2c 30  |,36,6,9.8,0.01,0|
00000020  2e 30 31 2c 31 30 2c 35  30 30 20 0a 50 61 73 74  |.01,10,500 .Past|
00000030  61 2c 33 34 37 2c 32 2e  35 2c 36 34 2c 31 33 2c  |a,347,2.5,64,13,|
...

文件无物料清单：

00000000  42 72 65 61 64 2c 32 31  32 2c 32 2e 37 2c 33 36  |Bread,212,2.7,36|
00000010  2c 36 2c 39 2e 38 2c 30  2e 30 31 2c 30 2e 30 31  |,6,9.8,0.01,0.01|
00000020  2c 31 30 2c 35 30 30 20  0a 50 61 73 74 61 2c 33  |,10,500 .Pasta,3|
00000030  34 37 2c 32 2e 35 2c 36  34 2c 31 33 2c 37 2c 30  |47,2.5,64,13,7,0|
...

Answer 2

很可能，除了具有该编码的 Byte Order Mark (BOM), the original copy of the foods.txt file was encoded using UTF-16, instead of ASCII or the more popular and compatible UTF-8. Taking a cue from wildplasser's answer, here is a hex dump of the first portion of the file in the little-endian 变体之外：

00000000  ff fe 42 00 72 00 65 00  61 00 64 00 2c 00 32 00  |..B.r.e.a.d.,.2.|
00000010  31 00 32 00 2c 00 32 00  2e 00 37 00 2c 00 33 00  |1.2.,.2...7.,.3.|
00000020  36 00 2c 00 36 00 2c 00  39 00 2e 00 38 00 2c 00  |6.,.6.,.9...8.,.|
00000030  30 00 2e 00 30 00 31 00  2c 00 30 00 2e 00 30 00  |0...0.1.,.0...0.|
00000040  31 00 2c 00 31 00 30 00  2c 00 35 00 30 00 30 00  |1.,.1.0.,.5.0.0.|
00000050  20 00 0a 00 50 00 61 00  73 00 74 00 61 00 2c 00  | ...P.a.s.t.a.,.|
00000060  33 00 34 00 37 00 2c 00  32 00 2e 00 35 00 2c 00  |3.4.7.,.2...5.,.|

前导 ff fe 代表字节顺序标记，并且会解释输出 name: ■B 中出现的神秘 ■。此后，每隔一个字节为 0，这就是“Bread”被截断为“B”的原因。然后 fscanf 的第一个 %lf 看到“r[=16=]e[=16=]a[=16=]d”，并且不能将其解析为双精度数，这就是为什么 fscanf returns 1 而不是 10.

Answer 3

将 .txt 文件的内容复制到新的 .txt 文件中解决了问题。它起源于一个 .xls 文件，我的猜测是，你们中的一些人提到的奇怪的 BOM 东西来自。

使用 fscanf，将文件扫描到 C 中的结构中，但第一个参数已经失败

Using fscanf, scanning a file into a struct in C, but the first argument is failing already

c

struct

byte-order-mark

scanf