Mini Shell

# Run an xterm on current process or a forked process

# Adapted from pty.py in Python 1.5.2 distribution.
# The pty.fork() couldnt be used because it didn't return
# the pty name needed by xterm
# I couldnt import pty.py to use master_open because it didn't find termios.

import os
import sys
import fcntl

# We couldnt find termios

STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO = 0, 1, 2

# Open pty master.  Returns (master_fd, tty_name).  SGI and Linux/BSD version.
# Copied from pty.py from Python 1.5.2. /SN


def master_open():
    try:
        import sgi
    except ImportError:
        pass
    else:
        try:
            tty_name, master_fd = sgi._getpty(fcntl.O_RDWR, 0o666, 0)
        except IOError as 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, fcntl.O_RDWR)
            except os.error:
                continue
            return (fd, '/dev/tty' + x + y)
    raise os.error('out of pty devices')

# Open the pty slave.  Acquire the controlling terminal.
# Returns file descriptor.  Linux version.  (Should be universal? --Guido)
# Copied from pty.py from Python 1.5.2. /SN


def slave_open(tty_name):
    return os.open(tty_name, fcntl.O_RDWR)


def xterm(prog=None, options=''):
    master_fd, tty_name = master_open()
    pid = os.fork()
    if pid:
        # Acquire controlling terminal.
        slave_fd = slave_open(tty_name)

        # 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)
        os.close(master_fd)
        sys.stdin.readline()  # Throw away an init string from xterm
        if prog is not None:
            prog()
    else:
        os.setsid()
        cmd = 'xterm %s -S%s%d' % (options, tty_name[-2:], master_fd)
        os.system(cmd)
        #os.waitpid(pid, 0)
    return pid


def forkxterm(prog=None, options=''):
    pid = os.fork()
    if pid:
        return pid
    else:
        os.setsid()
        pid = xterm(prog, options)
        if not pid:
            os._exit(0)


def hello():
    print('hello')
    while 1:
        pass