scanf()不接受任何输入

I have C code doing some calculations (irrelevant to my question, I believe ). The program will ask for some parameters for calculation. The problem is when I running the codes, a scanf("%c", &ch) isn't working properly.

我有C代码做一些计算(我认为与我的问题无关)。程序将要求一些参数进行计算。问题是当我运行代码时，一个scanf(“%c”，&ch)不能正常工作。

I'm interested in whether you can reproduce this problem because it seems that I didn't get anything wrong, am I?

我感兴趣的是你是否可以重现这个问题因为看起来我没有做错什么，是吗?

I posted an compilable and shortened version of my program.

我发布了我的程序的一个可编译和缩短版本。

#include<stdio.h>
#include<stdlib.h>
#include<math.h>
int main(void)
{
        float Dia_MM, Dia_I, Se1, Se, Sut = 75.00;
        float Ka, Kb, Kc, Kd, Ke, Kf;
        char Ch;
        char Bt;
        float Reli;
        printf("Please input the surface condition of the shaft: G, M, H or A\n");
        scanf("%c", &Ch);
//      getchar();
        printf("Please input the diameter of the shaft in inch\n");
        scanf("%f", &Dia_I);
        printf("Please specify whether your shaft is in bending (B) or torsion (T)");
        scanf("%c", &Bt);// THIS LINE IS JUST SKIPPED
        exit(0);
}

The GDB log is listed:

GDB日志列示:

  Breakpoint 1, main () at main.c:25
  25        float Dia_MM, Dia_I, Se1, Se, Sut = 75.00;
  (gdb) n
  30        printf("Please input the surface condition of the shaft: G, M, H or A\n");
  (gdb) n
  Please input the surface condition of the shaft: G, M, H or A
  31        scanf("%c", &Ch);
  (gdb) G
  Undefined command: "G".  Try "help".
  (gdb) n 
  G
  33        printf("Please input the diameter of the shaft in inch\n");
  (gdb) n
  Please       input the diameter of the shaft in inch
  34        scanf("%f", &Dia_I);
  (gdb) n
  4.5
  35        printf("Please specify whether your shaft is in bending (B) or torsion (T)");
  (gdb) n
  36            scanf("%c", &Bt);
  (gdb) n                            //PROBLEM HERE. SCANF() GOES BEFORE TAKE ANY INPUT.
  37        exit(0);

3 个解决方案

#1

scanf() does not consume trailing newlines. The skipped scanf() receives the newline from the previous line typed by the user and terminates without receiving more input as you would expect...

scanf()不消耗尾线。跳过的scanf()从用户输入的前一行接收换行，并在不接收更多输入的情况下终止。

scanf() is a bit cumbersome with newlines. A possible solution would be to use fgets() to get a line from the console and then employ sscanf() to parse the received string.

scanf()对于换行来说有点麻烦。一种可能的解决方案是使用fgets()从控制台获取一行，然后使用sscanf()解析接收到的字符串。

Another, more targeted, solution would be to use " %c" in the format string of the last scanf() call. The %c format specifier does not consume leading whitespace on its own, which is why it gets the remaining newline, rather than a character typed by the user.

另一个更有针对性的解决方案是在最后一次scanf()调用的格式字符串中使用“%c”。%c格式说明符本身不使用前导空白，这就是为什么它获得剩余的换行符，而不是用户键入的字符。

#2

As thkala told above scanf() does not consume trailing newlines.But there is another way to absorb the newline from the previous line using \n like that scanf("%c\n",...).

正如thkala在上面所说的，scanf()不消耗尾线。但是有另一种方法可以利用类似于scanf(“%c\n”，…)的\n从上一行中吸收换行。

#3

You can also use

您还可以使用

scanf(" %c",&c);

#1