checking a file if it exists or not before opening it

 #include<stdio.h>

int main()

{

    FILE *ptr;

    int n1,n2;

    ptr=fopen("ab.txt","r");

    if(ptr==NULL)

    {

printf("file doesnot exist");

    }

    else{

        fscanf(ptr,"%d",&n1);

                fscanf(ptr,"%d\n",&n2);

                fclose(ptr);

        printf("n1:%d\n",n1);

                printf("n2:%d",n2);

    }

    return 0;

}