Question

我想写一个小程序来学习C;这是：

#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;
}

当我跑步时，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]

该程序在运行时会跳过scanf("%[^\n]", info[counter].name);这行吗？

为什么，是什么导致它？

Answer 1

根据C标准，

fflush(stdin)未定义，但它适用于某些实现。但最好避免它，因为它不可移植，可能会调用未定义的行为。

要解决此问题，请将所有fflush(stdin)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);

并且应该将放在 for循环中。否则，您调用未定义的行为，因为

您通过了int* %d，希望int。
您访问分配的内存段之外的无效内存位置。

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

Answer 2

问题在于您的scanf模式。使用" %[^\n]"代替"%[^\n]"无法捕获\n（之前的数据输入后）
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＆＃39; Reilly Media

Understanding and Using C Pointers

scanf（“％[^ \ n]”）被跳过

2 个答案: