Does the input buffer gets cleared after scanf reads?

问题

Does the input buffer gets cleared after scanf reads?

#include <stdio.h>

int main(void) 
{
    int a, b;
    scanf("%d", &a);//I inputted 3
    scanf("%d", &b);//I inputted 4
}

So when I gave the input 4 was 3 present in the input buffer?

回答1:

So when I gave the input 4 was 3 present in the input buffer?

No, the 3 was consumed.

You cannot re-read it (as int or otherwise).

If you input "3<enter>" the 3 is consumed and the buffer contains just the "<enter>". You then type "4<enter>" which is added to the buffer. The 2nd scanf (*) consumes the initial enter and the 4 leaving "<enter>" for the next input operation.

(*) the conversion specifier "%d" skips optional leading whitespace and (tries to) converts the rest of the input to integer (if no errors occur).

回答2:

So when I gave the input 4 was 3 present in the input buffer?

No, it wasn't.

scanf() reads (and consumes) from the standard input until a match the specified format (in your case an integer) is found. That format is converted and consumed as well.

来源：https://stackoverflow.com/questions/61641084/does-the-input-buffer-gets-cleared-after-scanf-reads