"""Pseudo terminal utilities.""" # Bugs: No signal handling. Doesn't set slave termios and window size. # Only tested on Linux. # See: W. Richard Stevens. 1992. Advanced Programming in the # UNIX Environment. Chapter 19. # Author: Steen Lumholt -- with additions by Guido. from select import select import os import tty __all__ = ["openpty","fork","spawn"] STDIN_FILENO = 0 STDOUT_FILENO = 1 STDERR_FILENO = 2 CHILD = 0 def openpty(): """openpty() -> (master_fd, slave_fd) Open a pty master/slave pair, using os.openpty() if possible.""" try: return os.openpty() except (AttributeError, OSError): pass master_fd, slave_name = _open_terminal() slave_fd = slave_open(slave_name) return master_fd, slave_fd def master_open(): """master_open() -> (master_fd, slave_name) Open a pty master and return the fd, and the filename of the slave end. Deprecated, use openpty() instead.""" try: master_fd, slave_fd = os.openpty() except (AttributeError, OSError): pass else: slave_name = os.ttyname(slave_fd) os.close(slave_fd) return master_fd, slave_name return _open_terminal() def _open_terminal(): """Open pty master and return (master_fd, tty_name).""" for x in 'pqrstuvwxyzPQRST': for y in '0123456789abcdef': pty_name = '/dev/pty' + x + y try: fd = os.open(pty_name, os.O_RDWR) except OSError: continue return (fd, '/dev/tty' + x + y) raise OSError('out of pty devices') def slave_open(tty_name): """slave_open(tty_name) -> slave_fd Open the pty slave and acquire the controlling terminal, returning opened filedescriptor. Deprecated, use openpty() instead.""" result = os.open(tty_name, os.O_RDWR) try: from fcntl import ioctl, I_PUSH except ImportError: return result try: ioctl(result, I_PUSH, "ptem") ioctl(result, I_PUSH, "ldterm") except OSError: pass return result def fork(): """fork() -> (pid, master_fd) Fork and make the child a session leader with a controlling terminal.""" try: pid, fd = os.forkpty() except (AttributeError, OSError): pass else: if pid == CHILD: try: os.setsid() except OSError: # os.forkpty() already set us session leader pass return pid, fd master_fd, slave_fd = openpty() pid = os.fork() if pid == CHILD: # Establish a new session. os.setsid() os.close(master_fd) # Slave becomes stdin/stdout/stderr of child. os.dup2(slave_fd, STDIN_FILENO) os.dup2(slave_fd, STDOUT_FILENO) os.dup2(slave_fd, STDERR_FILENO) if (slave_fd > STDERR_FILENO): os.close (slave_fd) # Explicitly open the tty to make it become a controlling tty. tmp_fd = os.open(os.ttyname(STDOUT_FILENO), os.O_RDWR) os.close(tmp_fd) else: os.close(slave_fd) # Parent and child process. return pid, master_fd def _writen(fd, data): """Write all the data to a descriptor.""" while data: n = os.write(fd, data) data = data[n:] def _read(fd): """Default read function.""" return os.read(fd, 1024) def _copy(master_fd, master_read=_read, stdin_read=_read): """Parent copy loop. Copies pty master -> standard output (master_read) standard input -> pty master (stdin_read)""" fds = [master_fd, STDIN_FILENO] while True: rfds, wfds, xfds = select(fds, [], []) if master_fd in rfds: data = master_read(master_fd) if not data: # Reached EOF. fds.remove(master_fd) else: os.write(STDOUT_FILENO, data) if STDIN_FILENO in rfds: data = stdin_read(STDIN_FILENO) if not data: fds.remove(STDIN_FILENO) else: _writen(master_fd, data) def spawn(argv, master_read=_read, stdin_read=_read): """Create a spawned process.""" if type(argv) == type(''): argv = (argv,) pid, master_fd = fork() if pid == CHILD: os.execlp(argv[0], *argv) try: mode = tty.tcgetattr(STDIN_FILENO) tty.setraw(STDIN_FILENO) restore = 1 except tty.error: # This is the same as termios.error restore = 0 try: _copy(master_fd, master_read, stdin_read) except OSError: if restore: tty.tcsetattr(STDIN_FILENO, tty.TCSAFLUSH, mode) os.close(master_fd) return os.waitpid(pid, 0)[1]