Question

I have the following code lines :

printf("enter a number: \n");
if (scanf("%d", &x) == 1)
{ //do some stuff}
else {return 1;}
printf("enter another number: \n");
if (scanf("%d",&y) == 1)
{ //do some stuff}
else {return 1;}

the code works but when I'm putting an input to x in the following form "1 1" (1 then space then 1 again) it put the 2nd 1 into y. How can I make it won't happen? it should just stop the code.

I know there are other methods to get inputs but as for now, I'm only allowed to use scanf to get input from the user.

Answer 1

您正在看到scanf的正常行为。第二个1被读取第二个scanf因为%d会跳过空格，直到找到下一个数字为止转换。

在第一个scanf之后，这是输入缓冲区中剩下的内容

+-----+-----+------+
| ' ' | '1' | '\n' |
+-----+-----+------+

因此，如果您想在第一次转换后停止，则需要清除缓冲区。您可以使用此功能：

void clear_line(FILE *fp)
{
    if(fp == NULL)
        return;

    int c;
    while((c = fgetc(fp)) != '\n' && c != EOF);
}

然后你可以这样做：

printf("enter a number: \n");
if (scanf("%d", &x) == 1)
{ //do some stuff}
else {return 1;}

clear_line(stdin);

printf("enter another number: \n");
if (scanf("%d",&y) == 1)
{ //do some stuff}
else {return 1;}

clear_line(stdin);

在这种情况下，即使您输入1 1，第二个scanf也会等待用户输入

scanf validation of input also 1 scanf gets 2 inputs and send it to the next var without needing

1 个答案: