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@@ -0,0 +1,167 @@
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+import array
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+import fcntl
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+import os
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+import pty
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+import select
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+import signal
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+import sys
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+import termios
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+import tty
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+
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+# The following escape codes are xterm codes.
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+# See http://rtfm.etla.org/xterm/ctlseq.html for more.
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+START_ALTERNATE_MODE = set('\x1b[?{0}h'.format(i) for i in ('1049', '47', '1047'))
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+END_ALTERNATE_MODE = set('\x1b[?{0}l'.format(i) for i in ('1049', '47', '1047'))
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+ALTERNATE_MODE_FLAGS = tuple(START_ALTERNATE_MODE) + tuple(END_ALTERNATE_MODE)
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+
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+def findlast(s, substrs):
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+ '''
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+ Finds whichever of the given substrings occurs last in the given string
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+ and returns that substring, or returns None if no such strings
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+ occur.
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+ '''
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+ i = -1
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+ result = None
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+ for substr in substrs:
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+ pos = s.rfind(substr)
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+ if pos > i:
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+ i = pos
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+ result = substr
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+ return result
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+
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+class Interceptor(object):
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+ '''
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+ This class does the actual work of the pseudo terminal. The spawn()
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+ function is the main entrypoint.
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+ '''
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+
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+ def __init__(self):
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+ self.master_fd = None
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+
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+ def spawn(self, argv=None):
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+ '''
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+ Create a spawned process.
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+ Based on the code for pty.spawn().
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+ '''
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+ assert self.master_fd is None
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+ if not argv:
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+ argv = [os.environ['SHELL']]
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+
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+ pid, master_fd = pty.fork()
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+ self.master_fd = master_fd
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+ if pid == pty.CHILD:
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+ os.execlp(argv[0], *argv)
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+
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+ old_handler = signal.signal(signal.SIGWINCH, self._signal_winch)
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+ try:
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+ mode = tty.tcgetattr(pty.STDIN_FILENO)
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+ tty.setraw(pty.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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+ self._init_fd()
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+ try:
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+ self._copy()
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+ except (IOError, OSError):
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+ if restore:
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+ tty.tcsetattr(pty.STDIN_FILENO, tty.TCSAFLUSH, mode)
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+
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+ os.close(master_fd)
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+ self.master_fd = None
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+ signal.signal(signal.SIGWINCH, old_handler)
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+
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+ def _init_fd(self):
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+ '''
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+ Called once when the pty is first set up.
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+ '''
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+ self._set_pty_size()
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+
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+ def _signal_winch(self, signum, frame):
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+ '''
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+ Signal handler for SIGWINCH - window size has changed.
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+ '''
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+ self._set_pty_size()
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+
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+ def _set_pty_size(self):
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+ '''
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+ Sets the window size of the child pty based on the window size of
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+ our own controlling terminal.
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+ '''
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+ assert self.master_fd is not None
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+
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+ # Get the terminal size of the real terminal, set it on the pseudoterminal.
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+ buf = array.array('h', [0, 0, 0, 0])
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+ fcntl.ioctl(pty.STDOUT_FILENO, termios.TIOCGWINSZ, buf, True)
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+ fcntl.ioctl(self.master_fd, termios.TIOCSWINSZ, buf)
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+
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+ def _copy(self):
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+ '''
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+ Main select loop. Passes all data to self.master_read() or
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+ self.stdin_read().
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+ '''
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+ assert self.master_fd is not None
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+ master_fd = self.master_fd
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+ while 1:
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+ try:
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+ rfds, wfds, xfds = select.select([master_fd, pty.STDIN_FILENO], [], [])
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+ except select.error, e:
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+ if e[0] == 4: # Interrupted system call.
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+ continue
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+
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+ if master_fd in rfds:
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+ data = os.read(self.master_fd, 1024)
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+ self.master_read(data)
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+ if pty.STDIN_FILENO in rfds:
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+ data = os.read(pty.STDIN_FILENO, 1024)
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+ self.stdin_read(data)
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+
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+ def write_stdout(self, data):
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+ '''
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+ Writes to stdout as if the child process had written the data.
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+ '''
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+ os.write(pty.STDOUT_FILENO, data)
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+
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+ def write_master(self, data):
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+ '''
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+ Writes to the child process from its controlling terminal.
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+ '''
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+ master_fd = self.master_fd
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+ assert master_fd is not None
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+ while data != '':
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+ n = os.write(master_fd, data)
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+ data = data[n:]
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+
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+ def master_read(self, data):
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+ '''
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+ Called when there is data to be sent from the child process back to
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+ the user.
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+ '''
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+ flag = findlast(data, ALTERNATE_MODE_FLAGS)
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+ if flag is not None:
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+ if flag in START_ALTERNATE_MODE:
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+ # This code is executed when the child process switches the
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+ # terminal into alternate mode. The line below
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+ # assumes that the user has opened vim, and writes a
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+ # message.
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+ self.write_master('IEntering special mode.\x1b')
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+ elif flag in END_ALTERNATE_MODE:
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+ # This code is executed when the child process switches the
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+ # terminal back out of alternate mode. The line below
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+ # assumes that the user has returned to the command
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+ # prompt.
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+ self.write_master('echo "Leaving special mode."\r')
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+ self.write_stdout(data)
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+
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+ def stdin_read(self, data):
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+ '''
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+ Called when there is data to be sent from the user/controlling
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+ terminal down to the child process.
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+ '''
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+ print data + '_'
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+ self.write_master(data)
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+
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+if __name__ == '__main__':
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+ i = Interceptor()
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+ i.write_stdout('\nThe dream has begun.\n')
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+ i.spawn(sys.argv[1:])
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+ i.write_stdout('\nThe dream is (probably) over.\n')
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Johann Woelper