Comparing 2 files in c linux fgets

I need to compare 2 files and return 1 if they are same or 0 if not, but function always return 0. I have no idea why. Maybe you know diferent function that can do this.

int compare(char *file_1, char *file_2)
{
    FILE *data_1 = fopen(file_1,"r");
    FILE *data_2 = fopen(file_2,"r");
    char line1[1000];
    char line2[1000];
    while(fgets(line1, sizeof(line1), data_1)&&fgets(line2, sizeof(line2), data_2)){
        if(strcmp(line1,line2)==0){
          fclose(data_1);
          fclose(data_2);
          return 0;
        }
    }
    fclose(data_1);
    fclose(data_2);
    return 1;
}

Answer

strcmp(line1,line2)==0 means line1 and line2 are equals, your code supposes they are different

There is an other error, if a file is starts with the content of the other you consider the files are equals (supposing you corrected the strcmp)

---

I encourage you to check the result of the fopen in case at least one of them does not exist / cannot be open

---

a solution can be :

int compare(char *file_1, char *file_2)
{
  FILE *fp1 = fopen(file_1,"r");

  if (fp1 == 0)
    return 0;

  FILE *fp2 = fopen(file_2,"r");

  if (fp2 == 0) {
    fclose(fp1);
    return 0;
  }

  char line1[1000];
  char line2[1000];
  char * r1, * r2;
  int result;

  for (;;) {
    r1 = fgets(line1, sizeof(line1), fp1);
    r2 = fgets(line2, sizeof(line2), fp2);

    if ((r1 == 0) || (r2 == 0)) {
      result = (r1 == r2);
      break;
    }

    if (strcmp(line1,line2) != 0) {
      result = 0;
      break;
    }
  }

  fclose(fp1);
  fclose(fp2);

  return result;
}