scanf("%[^\n]") 被跳过

Question

我想写一个小程序来学习C；在这里：

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

int total;
char suffix[3];
struct person {
    char id[11];
    char name[21];
    char sex[7];
    int age;
    char phone[12];
};

char* number_suffix (int number) {
    int mod;
    mod = number % 10;

    switch (mod) {
        case 1:
            strcpy(suffix, "st");
            break;
        case 2:
            strcpy(suffix, "nd");
            break;
        case 3:
            strcpy(suffix, "rd");
            break;
        default:
            strcpy(suffix, "th");
            break;
    }
    return suffix;
}

void input_info (struct person info[], int total_people) {
    int counter;
    for (counter=0; counter<total_people; counter++){
        printf("%s%d%s%s\n","Please input the ID(10 digits) of ", (counter+1),
                number_suffix(counter), " person: ");
        scanf("%s", info[counter].id);
        fflush(stdin);

        printf("%s%d%s%s\n", "Please input the Name(20 chars) of ", (counter+1),
                number_suffix(counter), " person: ");
        scanf("%[^\n]", info[counter].name);
        fflush(stdin);

        printf("%s%d%s%s\n", "Please input the Sex(Male/Female) of ", (counter+1),
                number_suffix(counter), " person: ");
        scanf("%s", info[counter].sex);
        fflush(stdin);

        printf("%s%d%s%s\n", "Please input the Age(1~100) of ", (counter+1),
                number_suffix(counter), " person: ");
        scanf("%d", &info[counter].age);
        fflush(stdin);

        printf("%s%d%s%s\n", "Please input the Phone of ", (counter+1),
                number_suffix(counter), " person: ");
        scanf("%s", info[counter].phone);
        fflush(stdin);
    }
    printf("%s\n%s\n%s\n%d\n%s\n", info[counter].id, info[counter].name, info[counter].sex, &info[counter].age, info[counter].phone);
}

int main (void) {
    printf("%s\n", "Please input a number that how many people you want to record:");
    scanf("%d", &total);
    fflush(stdin);
    struct person *person_info = malloc(sizeof(struct person)*total);
    input_info(person_info, total);

    free(person_info);
    return 0;
}

当我运行它时，我发现了一些奇怪的东西。

Please input a number that how many people you want to record:
1
Please input the ID(10 digits) of 1th person:
A01
Please input the Name(20 chars) of 1th person:
Please input the Sex(Male/Female) of 1th person:
Male
Please input the Age(1~100) of 1th person:
32
Please input the Phone of 1th person:
1224464
[empty line]
[empty line]
[empty line]
1926234464
[empty line]

该程序在运行时是否跳过scanf("%[^\n]", info[counter].name); 这一行？

为什么，是什么原因造成的？

Answer 1

fflush(stdin) 根据 C 标准未定义，但它适用于某些实现。但最好避免使用它，因为它不可移植并且可能会调用未定义的行为。

要解决此问题，请将所有 fflush(stdin)s 替换为

int c; /* Declare it once */
while((c = getchar()) != '\n' && c != EOF); /* Discards everything until a newline character or EOF */

---

另一个问题是

printf("%s\n%s\n%s\n%d\n%s\n", info[counter].id, info[counter].name, info[counter].sex, &info[counter].age, info[counter].phone);

应该是

printf("%s\n%s\n%s\n%d\n%s\n", info[counter].id, info[counter].name, info[counter].sex, info[counter].age, info[counter].phone);

并且应该放在内 for 循环。否则，您会调用未定义的行为，因为

1. 您为 %d 传递了一个 int*，它需要一个 int。
2. 您访问了超出已分配内存段的无效内存位置。

---

另外，正如其他人所说，将counter + 1 传递给number_suffix。

Answer 2

1. 问题在于您的 scanf 模式。使用" %[^\n]" 而不是"%[^\n]" 来不捕获\n（在之前的数据输入之后）
2. 将counter + 1 传递给number_suffix

如何理解指针、struct、malloc、函数参数之间的关系？

从 O'Reilly Media

阅读 Understanding and Using C Pointers