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/Lib/pty.py

http://unladen-swallow.googlecode.com/
Python | 174 lines | 129 code | 20 blank | 25 comment | 8 complexity | 6c4c308ffc37f507c750c8efccf3d65b MD5 | raw file
  1"""Pseudo terminal utilities."""
  2
  3# Bugs: No signal handling.  Doesn't set slave termios and window size.
  4#       Only tested on Linux.
  5# See:  W. Richard Stevens. 1992.  Advanced Programming in the
  6#       UNIX Environment.  Chapter 19.
  7# Author: Steen Lumholt -- with additions by Guido.
  8
  9from select import select
 10import os
 11import tty
 12
 13__all__ = ["openpty","fork","spawn"]
 14
 15STDIN_FILENO = 0
 16STDOUT_FILENO = 1
 17STDERR_FILENO = 2
 18
 19CHILD = 0
 20
 21def openpty():
 22    """openpty() -> (master_fd, slave_fd)
 23    Open a pty master/slave pair, using os.openpty() if possible."""
 24
 25    try:
 26        return os.openpty()
 27    except (AttributeError, OSError):
 28        pass
 29    master_fd, slave_name = _open_terminal()
 30    slave_fd = slave_open(slave_name)
 31    return master_fd, slave_fd
 32
 33def master_open():
 34    """master_open() -> (master_fd, slave_name)
 35    Open a pty master and return the fd, and the filename of the slave end.
 36    Deprecated, use openpty() instead."""
 37
 38    try:
 39        master_fd, slave_fd = os.openpty()
 40    except (AttributeError, OSError):
 41        pass
 42    else:
 43        slave_name = os.ttyname(slave_fd)
 44        os.close(slave_fd)
 45        return master_fd, slave_name
 46
 47    return _open_terminal()
 48
 49def _open_terminal():
 50    """Open pty master and return (master_fd, tty_name).
 51    SGI and generic BSD version, for when openpty() fails."""
 52    try:
 53        import sgi
 54    except ImportError:
 55        pass
 56    else:
 57        try:
 58            tty_name, master_fd = sgi._getpty(os.O_RDWR, 0666, 0)
 59        except IOError, msg:
 60            raise os.error, msg
 61        return master_fd, tty_name
 62    for x in 'pqrstuvwxyzPQRST':
 63        for y in '0123456789abcdef':
 64            pty_name = '/dev/pty' + x + y
 65            try:
 66                fd = os.open(pty_name, os.O_RDWR)
 67            except os.error:
 68                continue
 69            return (fd, '/dev/tty' + x + y)
 70    raise os.error, 'out of pty devices'
 71
 72def slave_open(tty_name):
 73    """slave_open(tty_name) -> slave_fd
 74    Open the pty slave and acquire the controlling terminal, returning
 75    opened filedescriptor.
 76    Deprecated, use openpty() instead."""
 77
 78    result = os.open(tty_name, os.O_RDWR)
 79    try:
 80        from fcntl import ioctl, I_PUSH
 81    except ImportError:
 82        return result
 83    try:
 84        ioctl(result, I_PUSH, "ptem")
 85        ioctl(result, I_PUSH, "ldterm")
 86    except IOError:
 87        pass
 88    return result
 89
 90def fork():
 91    """fork() -> (pid, master_fd)
 92    Fork and make the child a session leader with a controlling terminal."""
 93
 94    try:
 95        pid, fd = os.forkpty()
 96    except (AttributeError, OSError):
 97        pass
 98    else:
 99        if pid == CHILD:
100            try:
101                os.setsid()
102            except OSError:
103                # os.forkpty() already set us session leader
104                pass
105        return pid, fd
106
107    master_fd, slave_fd = openpty()
108    pid = os.fork()
109    if pid == CHILD:
110        # Establish a new session.
111        os.setsid()
112        os.close(master_fd)
113
114        # Slave becomes stdin/stdout/stderr of child.
115        os.dup2(slave_fd, STDIN_FILENO)
116        os.dup2(slave_fd, STDOUT_FILENO)
117        os.dup2(slave_fd, STDERR_FILENO)
118        if (slave_fd > STDERR_FILENO):
119            os.close (slave_fd)
120
121        # Explicitly open the tty to make it become a controlling tty.
122        tmp_fd = os.open(os.ttyname(STDOUT_FILENO), os.O_RDWR)
123        os.close(tmp_fd)
124    else:
125        os.close(slave_fd)
126
127    # Parent and child process.
128    return pid, master_fd
129
130def _writen(fd, data):
131    """Write all the data to a descriptor."""
132    while data != '':
133        n = os.write(fd, data)
134        data = data[n:]
135
136def _read(fd):
137    """Default read function."""
138    return os.read(fd, 1024)
139
140def _copy(master_fd, master_read=_read, stdin_read=_read):
141    """Parent copy loop.
142    Copies
143            pty master -> standard output   (master_read)
144            standard input -> pty master    (stdin_read)"""
145    while 1:
146        rfds, wfds, xfds = select(
147                [master_fd, STDIN_FILENO], [], [])
148        if master_fd in rfds:
149            data = master_read(master_fd)
150            os.write(STDOUT_FILENO, data)
151        if STDIN_FILENO in rfds:
152            data = stdin_read(STDIN_FILENO)
153            _writen(master_fd, data)
154
155def spawn(argv, master_read=_read, stdin_read=_read):
156    """Create a spawned process."""
157    if type(argv) == type(''):
158        argv = (argv,)
159    pid, master_fd = fork()
160    if pid == CHILD:
161        os.execlp(argv[0], *argv)
162    try:
163        mode = tty.tcgetattr(STDIN_FILENO)
164        tty.setraw(STDIN_FILENO)
165        restore = 1
166    except tty.error:    # This is the same as termios.error
167        restore = 0
168    try:
169        _copy(master_fd, master_read, stdin_read)
170    except (IOError, OSError):
171        if restore:
172            tty.tcsetattr(STDIN_FILENO, tty.TCSAFLUSH, mode)
173
174    os.close(master_fd)