cpython/Lib/pty.py at 3.5 · python/cpython · GitHub

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"""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]

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