solab4pb3

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <limits.h>
#include <string.h>
#define MAX(a, b) a > b ? a : b
#define MIN(a, b) a < b ? a : b

int getFD(const char *const path, int flags, int perm) {
  int fd = open(path, flags, perm);
  if (fd < 0) {
    perror("Open err: ");
    exit(1);
  }
  return fd;
}

void closeFD(int fd) {
  if (close(fd) < 0) {
    perror("Close err: ");
    exit(1);
  }
}

int main(int argc, char *argv[]) {
  if (argc != 3) {
    fprintf(stderr, "Wrong usage!\n");
    exit(1);
  }

  int fd1 = getFD(argv[1], O_RDONLY, 0);

  int nr;
  int max = INT_MIN, min = INT_MAX;
  int cnt = 0, sum = 0;
  while (read(fd1, &nr, sizeof(int)) > 0) {
    min = MIN(min, nr);
    max = MAX(max, nr);
    sum += nr;
    cnt++;
  }

  int fd2 = getFD(argv[2], O_RDWR | O_CREAT, S_IWUSR | S_IRUSR);

  char template[50] = "";
  sprintf(template, " Min: %d\n Max: %d\n Mean: %lf\n", min, max, 1.0 * sum/cnt);
  size_t templateLen = strlen(template);
  if (write(fd2, template, templateLen) == -1) {
    perror("Write err: ");
    exit(1);
  }

  closeFD(fd1);
  closeFD(fd2);
  return 0;
}