/* Open a pty, fork a child that frobs the pty's settings then
   exec()s, and see what we get back in a short conversation with the
   child. */
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <termios.h>
#include <unistd.h>

void * lose (char *s)
{
  fprintf(stderr, "%d\n", errno);
  fprintf(stderr, "%s: %s\n", s, strerror(errno));
  exit(1);
}

/* set some flags on a terminal */
int set_noecho (int fd) 
{
  struct termios  stermios;

  if (tcgetattr(fd, &stermios) < 0) return 0;

  stermios.c_lflag &= ~(ECHO | ECHONL);
  stermios.c_iflag &= ~(BRKINT);
  stermios.c_iflag |= (ICANON|ICRNL);
  stermios.c_oflag |= (OPOST|ONLCR); /* We want CR/LF-terminated lines. */

  stermios.c_cc[VERASE]=0177;
  if (tcsetattr(fd, TCSANOW, &stermios) < 0) return 0;
  return 1;
}

/* For some reason, I need to declare this... */
extern char *ptsname();

/* Open a pty with a pipe(2)-like interface. */
int open_pty(int fildes[2])
{
  /* pty mumbojumbo */
  int mtrfd = open("/dev/ptmx", O_RDWR, 0);
  char *pts;
  int slvfd;
  if (mtrfd == -1) return -1;
  if (grantpt(mtrfd) != 0) return -1;
  if (unlockpt(mtrfd) != 0) return -1;

  if ((pts = ptsname(mtrfd)) == NULL) return -1;
  slvfd = open(pts, O_RDWR, 0666);
  if (slvfd == -1) return -1;
  
  fildes[0] = mtrfd;
  fildes[1] = slvfd;
  return 0;
}

/* yes, this is written somewhat strangely. */
int main (int argc, char **argv) 
{
  int fds[2];
  pid_t pid;

  (open_pty(fds) == 0) || lose("open_pty");

  /* make a test file. */
  (system("echo foo > openpty.test") == 0) || lose("system");

  pid = fork();
  if (pid < -1) lose("fork");
  if (pid == 0) {
    dup2(fds[1], 0);
    (set_noecho(0) != 0) || lose("set_noecho");
    dup2(fds[1], 1);
    dup2(fds[1], 2);
    close(fds[1]);
    execl("/bin/ed", "/bin/ed", "openpty.test", NULL);
  } else {
    FILE *f;
    int status;
    (f = fdopen(fds[0], "w+")) || lose("fdopen");
    printf("%d\n", fgetc(f));
    printf("%d\n", fgetc(f));
    printf("%d\n", fgetc(f));
    fprintf(f, "q\n");
    fflush(f);
    wait(&status);
    (unlink("openpty.test")==0) || lose("unlink");
  }
}

/*
Expected output (which I get on Linux and NetBSD)
52
13
10

What I get on Solaris:
52
10
52

That is, the child's terminal isn't converting newlines to CR/LFs.
*/