The shell in the xterm

Stelios Xanthakis sxanth at ceid.upatras.gr
Thu Oct 21 02:19:32 CEST 2004


Hi.

I'm trying to open an xterm in slave mode connected
to a pseudo tty with an interactive python shell.
This can be useful when working in a GUI to pop up
xterm'd shells. The program below is a first attempt.
It opens an xterm with an interactive python interpreter
in which we can even run "os.system ('bash')" and
call vi. However there are problems...

------------------------------------------------------
import os
import code
import thread
import time
import sys

STDIN_FILENO = 0
STDOUT_FILENO = 1
STDERR_FILENO = 2

CHILD = 0

def openpty ():
     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)

def slave_open(tty_name):
     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 IOError:
         pass
     return result

def fork():
     master_fd, slave_fdn = openpty()
     slave_fd = slave_open (slave_fdn)
     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, slave_fdn

def thrr (cmd):
     thread.start_new_thread (os.system, (cmd,))

pid, fd, n = fork ()

if pid > 0:
    print 'parent, reading', n[8:]
    cmd = 'xterm -S'+n[8:]+str (fd)
    thrr (cmd)
    time.sleep (3)
    print "Send a command to the xterm!"
    os.write (fd, 'print "Hi!"\n')
    time.sleep (10)
    print "leave..."
else:
     code.interact ()
     print "terminated"
     sys.exit (1)
---------------------------------------

This is wrong. The fact that the interactive interpreter is executed in 
a different process, means that it has its own data and cannot modify 
the main program's state.

If we use threads, because of CLONE_FILES, we can't connect the
thread's stdin/stdout to the pty.

There are other problems, like xterm complaining that it cannot
'stat /dev/pts/p0', how do we kill the xterm once the
code.interact() terminates, zombies, etc.

I'm confused. Ideas?

Stelios



More information about the Python-list mailing list