使用 freopen() 和 scanf() 从文件中读取一个 int

Question

I try to read an int from a file using freopen(). File in.txt simply have a number:1, but what I get in output is -858993460. My code is shown below:

#include <cstdio>
#pragma warning(disable:4996)
using namespace std;

int main()
{
    freopen("in.txt", "r", stdin);
    int t;
    scanf("%d", &t);
    printf("%d\n", t);
    return 0;
}

Why does scanf() not read from in.txt correctly?

Answer 1

rule #1, if you have file io then check the return values

int main()
{
    FILE * ret = freopen("in.txt", "r", stdin);
    if(ret == NULL){
       printf("failed to open file");
       return -1;
    }
    int t;
    scanf("%d", &t);
    printf("%d\n", t);
    return 0;
}

your code runs fine for me once I point it at a real file

also check the return from scanf

 int count = scanf("%d", &t); 
 if(count != 1){
     printf("bad number");
     return -1;
 }