%d 占位符输入“3abc”，无法清除 'abc' 缓冲区

Question

下面是我的代码：

int length;
char ch;

printf("\n\tEnter the length of the password: ");
while (scanf("%d", &length) != 1) {

    printf("\n\tPlease enter digit only.\n");
    printf("\n\tEnter the length of the password: ");

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

printf("\n\tEnter the number of passwords you want: ");
while (scanf("%d", &num) != 1) {

    printf("\n\tPlease enter digit only.\n");
    printf("\n\tEnter the number of passwords you want: ");

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

当我输入的时候abc okay.

当我输入3abc时，按长度收到3，但'abc'还在缓冲区中。

我用while ((ch = getchar()) != '\n' && ch != EOF);清除了还是不行？

感谢专家的任何帮助。

Answer 1

如果 scanf 正确抓取了一个数字作为您的测试用例 3asc

，则您不会刷新 stdin

 int length;
 int ch;

 printf("\n\tEnter the length of the password: ");
 while (scanf("%d", &length) != 1) {

     printf("\n\tPlease enter digit only.\n");
     printf("\n\tEnter the length of the password: ");

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

 // flush stdin
 while ((ch = getchar()) != '\n' && ch != EOF);

 printf("\n\tEnter the number of passwords you want: ");
 while (scanf("%d", &length) != 1) {

     printf("\n\tPlease enter digit only.\n");
     printf("\n\tEnter the number of passwords you want: ");

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

并且，已经评论过，要识别ch != EOFch必须int。此外getchar原型是int getchar(void)

Answer 2

如果scanf()成功，循环内的内容不会被执行...所以如果你输入“3abc”，scanf()读取'3'而"abc"是仍在输入缓冲区中，因为您没有进入循环

%d 占位符输入“3abc”，无法清除 'abc' 缓冲区

%d placeholder input '3abc', cannot clear 'abc' buffer

c

buffer

stdin

flush