solab4pb4

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

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

void closeFD(int fd) {
  if (close(fd) < 0) {
    perror("");
    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);

  unsigned sof;
  unsigned on1b = 0, on2b = 0, on4b = 0;
  unsigned min = UINT_MAX, max = 0;
  unsigned long long sum = 0;
  while (read(fd1, &sof, 1) > 0) {
    unsigned len, data;
    read(fd1, &len, 1);
    read(fd1, &data, len);
    switch (len) {
    case 1:
      on1b++;
      break;
    case 2:
      on2b++;
      break;
    case 4:
      on4b++;
      break;
    }
    min = MIN(min, data);
    max = MAX(max, data);
    sum += data;
  }
  closeFD(fd1);

  int fd2 = getFD(argv[2], O_RDWR | O_CREAT, S_IWUSR | S_IRUSR);
  static char ans[50];

  sprintf(ans, "min: %u\n", min);
  write(fd2, ans, strlen(ans));
  sprintf(ans, "max: %u\n", max);
  write(fd2, ans, strlen(ans));
  sprintf(ans, "avg: %g\n", 1. * sum / (on1b + on2b + on4b));
  write(fd2, ans, strlen(ans));
  sprintf(ans, "1 byte ints: %u\n", on1b);
  write(fd2, ans, strlen(ans));
  sprintf(ans, "2 byte ints: %u\n", on2b);
  write(fd2, ans, strlen(ans));
  sprintf(ans, "4 byte ints: %u\n", on4b);
  write(fd2, ans, strlen(ans));

  close(fd2);
  return 0;
}