[英]C Programming - Calling fgets() twice?
In my C program, I call fgets()
twice to get input from the user. 在我的C程序中,我调用
fgets()
两次以获取用户的输入。 However, on the second call of fgets()
(which is in a function), it doesn't wait for the input to be taken, it just skips over it as if it didn't even ask for it. 但是,在第二次调用
fgets()
(在函数中)时,它不会等待输入,它只是跳过它就像它甚至没有要求它一样。 Here is my code (shortened down a bit): 这是我的代码(缩短了一点):
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define ARE_EQUAL 0
void rm_nl(char *c, int s);
float ctof();
float ftoc();
int main()
{
char str[2]; // Setting vars
float result;
printf("Type 'C' or 'F': "); // Prompt
fgets(str, 2, stdin); // <-- First fgets
rm_nl(str, 2); // rm_nl() removes the newline
// from input
printf("\n");
if(strcmp(str, "C") == ARE_EQUAL || strcmp(str, "c") == ARE_EQUAL)
{
result = ctof(); // Compares strings and calls
printf("%.2f\n", result); // function conditionally
}
else
{
result = ftoc();
printf("%.2f\n", result);
}
return 0;
}
float ctof() // One of the two functions
{ // (they are almost the same)
char input[64];
float fahr, cels; // Local vars
printf("Type in a Celsius value: "); // Prompt
fgets(input, 64, stdin); // <-- Second fgets
rm_nl(input, sizeof(input));
// Yadda yadda yadda
}
// Second function and rm_nl() not shown for readability
This program would output something like: 该程序将输出如下内容:
Type 'C' or 'F': (value)
and then... 然后...
Type a Celsius value: 57.40 (I don't type this)
(Program terminates)
It fills in the 57.40 without me even typing it! 即使输入它,它也没有我填充57.40! What should I do differently?
我该怎么办?
fgets(str, 2, stdin);
You're providing too little space for fgets
. 你为
fgets
提供的空间太小了。 You only allow it to read one character (since 2
includes the 0-terminator). 您只允许它读取一个字符(因为
2
包含0终结符)。
The newline will always be left in the input buffer so the next stdio operation will read it. 换行符将始终保留在输入缓冲区中,以便下一个stdio操作将读取它。
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