Question

I have a program called test.c, and an input file called test.in. I’m trying to read two strings from the input file and output them to the console. I’m running Windows 7 but I’m compiling with MinGW using gcc.

This is my file test.c:

#include <stdio.h>
main() {

    FILE *fin = fopen ("test.in", "r");
    char  *one, *two;

    fscanf(fin, "%s %s", one, two);
    printf("%s\n%s", one, two);

    fclose(fin);
    return 0;
}

And this is my file test.in :

ONE
TWO

I go to MinGW, run “gcc -o test.exe test.c”, everything compiles fine, but when I run test.exe, a pop-up comes up and says “test.exe has stopped working. Windows is trying to find a solution to the problem…”

Does anyone know why this is?

Answer 1

fscanf is writing to the uninitialised pointers you pass it. The effects of this are undefined but a crash is likely. You need to allocate your char arrays before calling it:

#define MAX_LEN (32) /* change this as required */
char one[MAX_LEN];
char two[MAX_LEN];
fscanf(fin, "%s %s", one, two);