"""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,error
import os
# Absurd: import termios and then delete it. This is to force an attempt
# to import pty to raise an ImportError on platforms that lack termios.
# Without this explicit import of termios here, some other module may
# import tty first, which in turn imports termios and dies with an
# ImportError then. But since tty *does* exist across platforms, that
# leaves a damaged module object for tty in sys.modules, and the import
# of tty here then appears to work despite that the tty imported is junk.
import termios
del termios
import tty
__all__ = ["openpty","fork","spawn","th_spawn","popen2"]
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).
SGI and generic BSD version, for when openpty() fails."""
try:
import sgi
except ImportError:
pass
else:
try:
tty_name, master_fd = sgi._getpty(os.O_RDWR, 0666, 0)
except IOError, msg:
raise os.error, msg
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 os.error:
continue
return (fd, '/dev/tty' + x + y)
raise os.error, '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."""
return os.open(tty_name, os.O_RDWR)
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)
# 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, stdin_fd=STDIN_FILENO,
stdout_fd=STDOUT_FILENO):
"""Parent copy loop.
Copies
pty master -> stdout_fd (master_read)
stdin_fd -> pty master (stdin_read)"""
try:
mode = tty.tcgetattr(stdin_fd)
tty.setraw(stdin_fd)
restore = 1
except tty.error: # This is the same as termios.error
restore = 0
try:
while 1:
rfds, wfds, xfds = select(
[master_fd, stdin_fd], [], [])
if master_fd in rfds:
data = master_read(master_fd)
os.write(stdout_fd, data)
if stdin_fd in rfds:
data = stdin_read(stdin_fd)
_writen(master_fd, data)
except (IOError, OSError, error): # The last entry is select.error
if restore:
tty.tcsetattr(stdin_fd, tty.TCSAFLUSH, mode)
if stdin_fd > STDERR_FILENO:
os.close(stdin_fd)
if stdout_fd > STDERR_FILENO:
os.close(stdout_fd)
def spawn(argv, master_read=_read, stdin_read=_read, stdin_fd=STDIN_FILENO,
stdout_fd=STDOUT_FILENO):
"""Create a spawned process. The controlling terminal reads and
writes its data to stdin_fd and stdout_fd respectively.
NOTE: This function does not return until one of the input or output file
descriptors are closed, or the child process exits."""
if type(argv) == type(''):
argv = (argv,)
pid, master_fd = fork()
if pid == CHILD:
apply(os.execlp, (argv[0],) + argv)
_copy(master_fd, master_read, stdin_read, stdin_fd, stdout_fd)
def th_spawn(argv, master_read=_read, stdin_read=_read, stdin_fd=STDIN_FILENO,
stdout_fd=STDOUT_FILENO):
"""Create a spawned process. The controlling terminal reads and
writes its data to stdin_fd and stdout_fd respectively. The function
returns the pid of the spawned process. (It returns immediately.)"""
import thread
if type(argv) == type(''):
argv = (argv,)
pid, master_fd = fork()
if pid == CHILD:
apply(os.execlp, (argv[0],) + argv)
thread.start_new_thread(_copy, (master_fd, master_read, stdin_read, \
stdin_fd, stdout_fd))
return pid
def popen2(cmd, bufsize=1024, master_read=_read, stdin_read=_read):
"""Execute the shell command 'cmd' in a sub-process.
If 'bufsize' is specified, it sets the buffer size for the I/O pipes.
The function returns (child_stdin, child_stdout, child_pid), where the
file objects are pipes connected to the spawned process's controling
terminal, and the child_pid is the pid of the child process.
"""
argv = ('/bin/sh', '-c', cmd)
child_stdin_rfd, child_stdin_wfd = os.pipe()
child_stdout_rfd, child_stdout_wfd = os.pipe()
child_pid = th_spawn(argv, master_read, stdin_read, child_stdin_rfd, \
child_stdout_wfd)
child_stdin = os.fdopen(child_stdin_wfd, 'w', bufsize)
child_stdout = os.fdopen(child_stdout_rfd, 'r', bufsize)
return child_stdin, child_stdout, child_pid
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