pb2 ex simplified

#include <stdio.h>
#include <stdlib.h>
#define IFILE "in.txt"
#define OFILE "out.txt"

FILE *openFile(char path[], char mode[]) {
  FILE *f = NULL;
  if ((f = fopen(path, mode)) == NULL) {
    perror("");
    exit(-1);
  }
  return f;
}

void closeFile(FILE *f) {
  if (fclose(f) == EOF) {
    perror("");
  }
}

int expr(FILE *fin) {
  int a, b;
  fscanf(fin, "%d", &a);
  for (int i = 0; i < 3; i++) fgetc(fin);
  fscanf(fin, "%d", &b);
  return a + b;
}

int main(void) {
  FILE *fin = openFile(IFILE, "r");
  FILE *fout = openFile(OFILE, "w");

  int id;
  while (fscanf(fin, "%d", &id) == 1) {
    fprintf(fout, "id: %d\n", id);
    int sum = expr(fin);
    fprintf(fout, "res=%d", sum);

    for (int last = 0, curr = 0; (curr = fgetc(fin)); last = curr) {
      if (curr == EOF) {
        break;
      }
      fputc(curr, fout);
      if (last == curr && last == '\n') {
        break;
      }
    }
  }

  closeFile(fin);
  closeFile(fout);
  return 0;
}

/*
pattern:
1
2 + 3
afkr
frftgeth
hryh

2
3 + 4
grs
grff
ff

 */