#define _XOPEN_SOURCE 600
#include <termios.h>
#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>

#include <stdio.h>
#include <string.h>

#define check(x) if ((x) == -1) {       \
    perror(#x); \
    exit(1); \
  }

int main()
{
  int ptymfd = posix_openpt(O_RDWR);
  check(ptymfd);
  check(grantpt(ptymfd));
  check(unlockpt(ptymfd));
  char *slavename = ptsname(ptymfd);
  printf("pty = %s\n", slavename);

  while (1)
    {
      char ch;
      int r = read(ptymfd, &ch, 1);
      check(r);
      if ('A' <= ch && ch < 'Z')
        ch++;
      int w = write(ptymfd, &ch, 1);
      check(w);
    }
  
  return EXIT_SUCCESS;
}