command line arrow key detection without termios.h

#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <unistd.h>

#define stdin 0
#define stdout 1
#define __KERNEL_NCCS 19
#define ICANON 0000002
#define ECHO   0000010

typedef unsigned int tcflag_t;
typedef unsigned char cc_t;

int printf(const char*, ...);

struct linux_termios {
  tcflag_t c_iflag;         /* Input flags */
  tcflag_t c_oflag;         /* Output flags */
  tcflag_t c_cflag;         /* Control mode flags */
  tcflag_t c_lflag;         /* Local mode flags  */
  cc_t c_line;              /* Line discipline */
  cc_t c_cc[__KERNEL_NCCS]; /* Control characters */
};

struct linux_termios termios_orig;

void backup_termios() {
  struct linux_termios l_termios;

  ioctl(stdin, TCGETS, &l_termios);

  memcpy(&termios_orig, &l_termios, sizeof(struct linux_termios));
  memcpy(&termios_orig.c_cc[0], &l_termios.c_cc[0], __KERNEL_NCCS);
}

struct linux_termios get_termios() {
  struct linux_termios l_termios;
  ioctl(stdin, TCGETS, &l_termios);

  return l_termios;
}

void enable_raw_mode() {
  struct linux_termios termios = get_termios();
  termios.c_lflag &= ~(ECHO | ICANON);
  ioctl(stdin, TCSETSF, &termios);
}

void revert_termios() {
  ioctl(stdin, TCSETSF, &termios_orig);
}

int main() {
  backup_termios();
  enable_raw_mode();
  atexit(revert_termios);

  char buf;
  while(read(stdin, &buf, 1) == 1 && buf != 'q') {
    if (buf == 27) {
      // Arrow key pressed, skip '['
      read(stdin, &buf, 1);

      read(stdin, &buf, 1);
      switch (buf) {
        case 'A': {
          write(stdout, "U", 1);
          break;
        }
        case 'B': {
          write(stdout, "D", 1);
          break;
        }
        case 'C': {
          write(stdout, "L", 1);
          break;
        }
        case 'D': {
          write(stdout, "R", 1);
          break;
        }
        default: write(stdout, &buf, 1);
      }
    }
  }

  return 0;
}