c - C 中的 Fscanf 用于存储文件中的数据

Question

这是我的代码。

#include<stdio.h>

struct element {
    int value;
    char activity;
};

typedef struct element element;

int main(int argc,char** argv) {
    FILE* fp;
    fp = fopen(argv[1], "r");

    element a;

    while(feof(fp) == 0) {
        fscanf(fp, "%c %d", &a.activity, &a.value);

        printf("\n%d", a.value);
    }
}

现在，它两次输出文件中的每个整数..

我怎么会得到这个奇怪的答案？

我的结构是:

struct element {
    int value;
    char activity;
};

typedef struct element element;

我的输入文件是:

i 23
i 56
i 19
i 20
i 44

Answer 1

查看您的 fscanf 模式:

fscanf(fp, "%c,%d", &a.activity, &a.value);

然后在你的文件格式:

i 23
i 56
i 19
i 20
i 44

我没有看到任何逗号。尝试使用空格，并确保考虑到换行符:

fscanf(fp, "%c %d\n", &a.activity, &a.value);

请记住 fscanf 不只是按顺序读取值，它会考虑通配符周围的固定字符。

编辑——同样重要，Keith 在评论中指出:

Note that using \n in the fscanf format string may be slightly misleading. Any white-space character (including \n) matches zero or more white-space characters. So adding the \n works for the given input -- but it would also work if the input were all on one line separated by spaces or tabs: i 23 i 56 i 19 i 20 i 44. If you really want line-oriented input, use fgets() (not gets()) to read a line at a time into a string, then sscanf() to parse the string. (All the *scanf() functions have problems with numeric overflow, though.)

希望对您有所帮助!

(PS:哦，我修正了你的代码格式。下次你发帖时，花点时间确保代码看起来正确缩进和东西。看到一个困惑的代码片段有点消除回答的欲望，你会在你的问题中得到的反馈要少得多!)