C 结构不扫描所有输入

Question

我有这个 C 代码:

#include "stdio.h"

main()
{
    struct books
    {
        char name[100],author[100];
        int year,copies;
    }book1,book2;

    printf("Enter details of first book\n");
    gets(book1.name);
    gets(book1.author);
    scanf("%d%d",&book1.year,&book1.copies);

    printf("Enter details for second book\n");
    gets(book2.name);
    gets(book2.author);
    scanf("%d%d",&book2.year,&book2.copies);

    printf("%s\n%s\n%d\n%d\n",book1.name,book1.author,book1.year,book1.copies);
    printf("%s\n%s\n%d\n%d\n",book2.name,book2.author,book2.year,book2.copies);  
}  

这里发生的事情是它只扫描到第二本书的作者姓名。之后它直接打印输出。

这是我的输入:(前两行是初始 printf 语句)

Enter details of first book
warning: this program uses gets(), which is unsafe.
the c programmign laguagne
dfadsda
3432
23
Enter details for second book
ruby on rails
mark hammers  

之后它直接打印输出:

the c programmign laguagne
dfadsda
3432
23

ruby on rails
0
0

这里出了什么问题？我们还可以看到第二本书的名字被分配给作者。

我使用 gcc 作为 Mac OS X ML 上的编译器。

Answer 1

使用fflush(stdin)在每个输入语句之前。该方法将清除输入缓冲区。 修改后您的代码将是 -

#include "stdio.h"

int main()
{
    struct books
    {
        char name[100],author[100];
        int year,copies;
    }book1,book2;

    printf("Enter details of first book\n");
    gets(book1.name);
    fflush(stdin);

    gets(book1.author);
    fflush(stdin);

    scanf("%d%d",&book1.year,&book1.copies);
    fflush(stdin);

    printf("Enter details for second book\n");
    gets(book2.name);
    fflush(stdin);

    gets(book2.author);
    fflush(stdin);
    scanf("%d%d",&book2.year,&book2.copies);

    printf("%s\n%s\n%d\n%d\n",book1.name,book1.author,book1.year,book1.copies);
    printf("%s\n%s\n%d\n%d\n",book2.name,book2.author,book2.year,book2.copies);  
    return 0;
} 

您可以查看 fflush() 的详细信息here .

更新: 在 scanf() 语句之后，您需要刷新输入缓冲区。 fflush() 方法在这里没有用，因为它仅为输出流定义。您可以在每个 scanf() 行之后使用单行代码来使用部分读取的行的其余部分，例如 -

while((c = getchar()) != '\n' && c != EOF);

你的代码将是:

#include "stdio.h"

int main()
{
    struct books
    {
        char name[100],author[100];
        int year,copies;
    }book1,book2;
    char c;
    printf("Enter details of first book\n");
    gets(book1.name);
    gets(book1.author);

    scanf("%d%d",&book1.year,&book1.copies);
    while((c = getchar()) != '\n' && c != EOF);

    printf("Enter details for second book\n");
    gets(book2.name);
    gets(book2.author);
    scanf("%d%d",&book2.year,&book2.copies);
    while((c = getchar()) != '\n' && c != EOF);

    printf("%s\n%s\n%d\n%d\n",book1.name,book1.author,book1.year,book1.copies);
    printf("%s\n%s\n%d\n%d\n",book2.name,book2.author,book2.year,book2.copies);  
    return 0;
} 

输出:

Enter details of first book
warning: this program uses gets(), which is unsafe.
sadsadas
asa
12
34
Enter details for second book
zxczxc
sds
23
22
sadsadas
asa
12
34
zxczxc
sds
23
22