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Reading ints from a file with C

This is a very simple question, but I cannot find something about it here. I want to read two integers from a file with C. Now my code is:

int main() {
    FILE *fp;
    int s[80];
    int t;

    if((fp=fopen("numbers", "r")) == NULL) {
        printf("Cannot open file.\n");
    } else {
        fscanf(fp, "%d%d", s, &t);
        printf("%d %d\n", s[0], s[1]);
    }

return 0;
}

I am getting the first integer from the file, but the next one is just a random number. My file looks like this:

100 54

Thank you in advance

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6 answers


This line:

fscanf(fp, "%d%d", s, &t);


puts one of an int in s[0]

and the other in t

, but you print s[0]

(which is your first int) and s[1]

that is uninitialized (and therefore "random").

+6


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Are you reading the results in s and t, but only printing s?



+3


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Your problem is this line:

fscanf(fp, "%d%d", s, &t);
printf("%d %d\n", s[0], s[1]);

You read s [0] and t, but you print s [0] and s [1]. Any of the following will work as a replacement:

fscanf(fp, "%d%d", s, &t);
printf("%d %d\n", s[0], t);

Or:

fscanf(fp, "%d%d", &s[0], &s[1]);
printf("%d %d\n", s[0], s[1]);
+2


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You never initialize it. You are passing a pointer to s

, which means (here) the first element, as the first parameter. What do you expect to see in s[1]

?

+1


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When you execute fscanf, you are using one set of variables. But when you do printf you are using a different one.

One way to make it work correctly:

#include "stdio.h"
int main()
{
  FILE *fp;
  int s[80];

  if((fp=fopen("numbers", "r")) == NULL) {
    printf("Cannot open file.\n");
  } else {
    fscanf(fp, "%d%d", &s[0], &s[1]);
    printf("%d %d\n", s[0], s[1]);
  }

  return 0;
}
+1


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You need to read in &s[0]

and &s[1]

or print s[0]

and t

.

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