求助C程序

# include <stdio.h>
# include <conio.h>
# include <math.h>
# include <stdlib.h>

long gmval(int m)
{
long s;
int i;
while(++m)
{
for(i=2;i<=sqrt(m);++i)
if(m%i==0) break;
if(i<=sqrt(m)) continue;
i=m;
s=0;
while(i)
{
s=s*10+i%10;
i/=10;
}
if(m==s) break;
}
return m;
}

void main()
{
int m;
long k;
FILE *fp;
if((fp=fopen("myf2.out","w"))==NULL)
{
printf("can't open the file");
exit(0);
}
scanf("%d",&m);
k=gmval(m);
printf("m=%d,%ld\n",m,k);
fprintf(fp,"m=%d,%ld\n",m,k);
fprintf(fp,"\nMy exam nimber is :0112400123\n");
fclose(fp);
getch();
}
程序中倒数第四行为什么fprintf不能输出结果？

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