Question

我正在遵循C Primer Plus的说明并组成以下代码：

#include <stdio.h>
int main(void) {
    int num;
    int x = scanf("%d", &num);
    printf("%d", x);
}

运行时：

$ ./a.out
t
0
$ ./a.out
2
1

scanf如何检测到“ 0”或“ 1”的值？

Answer 1

它不会检测到该值，而是将其返回。它读取一个整数并将其放入num中。 scanf的返回值不是它从用户输入中读取的值，而是读取的值数，在您的情况下，最大为1。

Answer 2

scanf被定义为

成功时，该函数返回成功读取的项目数。如果发生匹配失败，则此计数可以匹配预期的读数数或更少，甚至零。如果在输入数据失败之前无法成功读取任何数据，则返回EOF。

NAME
           scanf,  fscanf, sscanf, vscanf, vsscanf, vfscanf 

       ...

RETURN VALUE
       These functions return the number of input items  successfully  matched
       and assigned, which can be fewer than provided for, or even zero in the
       event of an early matching failure.

       The value EOF is returned if the end of input is reached before  either
       the  first  successful conversion or a matching failure occurs.  EOF is
       also returned if a read error occurs, in which case the error indicator
       for  the  stream  (see ferror(3)) is set, and errno is set indicate the
       error.

scanf（“％d”，＆num）的状态为0或1

2 个答案: