"""Pseudo terminal utilities."""

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# Bugs: No signal handling. Doesn't set slave termios and window size.

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# Only tested on Linux.

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# See: W. Richard Stevens. 1992. Advanced Programming in the

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# UNIX Environment. Chapter 19.

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# Author: Steen Lumholt -- with additions by Guido.

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from select import select

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import os

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import sys

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import tty

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__all__ = ["openpty","fork","spawn"]

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STDIN_FILENO = 0

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STDOUT_FILENO = 1

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STDERR_FILENO = 2

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CHILD = 0

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def openpty():

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"""openpty() -> (master_fd, slave_fd)

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Open a pty master/slave pair, using os.openpty() if possible."""

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try:

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return os.openpty()

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except (AttributeError, OSError):

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pass

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master_fd, slave_name = _open_terminal()

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slave_fd = slave_open(slave_name)

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return master_fd, slave_fd

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def master_open():

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"""master_open() -> (master_fd, slave_name)

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Open a pty master and return the fd, and the filename of the slave end.

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Deprecated, use openpty() instead."""

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try:

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master_fd, slave_fd = os.openpty()

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except (AttributeError, OSError):

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pass

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else:

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slave_name = os.ttyname(slave_fd)

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os.close(slave_fd)

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return master_fd, slave_name

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return _open_terminal()

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def _open_terminal():

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"""Open pty master and return (master_fd, tty_name)."""

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for x in 'pqrstuvwxyzPQRST':

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for y in '0123456789abcdef':

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pty_name = '/dev/pty' + x + y

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try:

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fd = os.open(pty_name, os.O_RDWR)

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except OSError:

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continue

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return (fd, '/dev/tty' + x + y)

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raise OSError('out of pty devices')

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def slave_open(tty_name):

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"""slave_open(tty_name) -> slave_fd

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Open the pty slave and acquire the controlling terminal, returning

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opened filedescriptor.

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Deprecated, use openpty() instead."""

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result = os.open(tty_name, os.O_RDWR)

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try:

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from fcntl import ioctl, I_PUSH

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except ImportError:

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return result

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try:

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ioctl(result, I_PUSH, "ptem")

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ioctl(result, I_PUSH, "ldterm")

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except OSError:

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pass

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return result

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def fork():

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"""fork() -> (pid, master_fd)

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Fork and make the child a session leader with a controlling terminal."""

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try:

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pid, fd = os.forkpty()

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except (AttributeError, OSError):

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pass

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else:

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if pid == CHILD:

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try:

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os.setsid()

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except OSError:

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# os.forkpty() already set us session leader

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pass

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return pid, fd

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master_fd, slave_fd = openpty()

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pid = os.fork()

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if pid == CHILD:

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# Establish a new session.

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os.setsid()

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os.close(master_fd)

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# Slave becomes stdin/stdout/stderr of child.

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os.dup2(slave_fd, STDIN_FILENO)

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os.dup2(slave_fd, STDOUT_FILENO)

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os.dup2(slave_fd, STDERR_FILENO)

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if (slave_fd > STDERR_FILENO):

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os.close (slave_fd)

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# Explicitly open the tty to make it become a controlling tty.

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tmp_fd = os.open(os.ttyname(STDOUT_FILENO), os.O_RDWR)

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os.close(tmp_fd)

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else:

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os.close(slave_fd)

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# Parent and child process.

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return pid, master_fd

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def _writen(fd, data):

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"""Write all the data to a descriptor."""

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while data:

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n = os.write(fd, data)

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data = data[n:]

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def _read(fd):

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"""Default read function."""

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return os.read(fd, 1024)

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def _copy(master_fd, master_read=_read, stdin_read=_read):

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"""Parent copy loop.

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Copies

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pty master -> standard output (master_read)

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standard input -> pty master (stdin_read)"""

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fds = [master_fd, STDIN_FILENO]

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while True:

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rfds, wfds, xfds = select(fds, [], [])

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if master_fd in rfds:

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data = master_read(master_fd)

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if not data: # Reached EOF.

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fds.remove(master_fd)

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else:

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os.write(STDOUT_FILENO, data)

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if STDIN_FILENO in rfds:

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data = stdin_read(STDIN_FILENO)

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if not data:

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fds.remove(STDIN_FILENO)

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else:

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_writen(master_fd, data)

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def spawn(argv, master_read=_read, stdin_read=_read):

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"""Create a spawned process."""

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if type(argv) == type(''):

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argv = (argv,)

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sys.audit('pty.spawn', argv)

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pid, master_fd = fork()

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if pid == CHILD:

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os.execlp(argv[0], *argv)

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try:

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mode = tty.tcgetattr(STDIN_FILENO)

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tty.setraw(STDIN_FILENO)

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restore = 1

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except tty.error: # This is the same as termios.error

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restore = 0

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try:

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_copy(master_fd, master_read, stdin_read)

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except OSError:

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if restore:

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tty.tcsetattr(STDIN_FILENO, tty.TCSAFLUSH, mode)

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os.close(master_fd)

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return os.waitpid(pid, 0)[1]

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