Lib/pty.py

   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
   9 from select import select
  10 import os
  11 import tty
  12
  13 __all__ = ["openpty","fork","spawn"]
  14
  15 STDIN_FILENO = 0
  16 STDOUT_FILENO = 1
  17 STDERR_FILENO = 2
  18
  19 CHILD = 0
  20
  21 def 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
  33 def 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
  49 def _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, 0o666, 0)
  59         except IOError as 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
  72 def 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
  90 def 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
 130 def _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
 136 def _read(fd):
 137     """Default read function."""
 138     return os.read(fd, 1024)
 139
 140 def _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
 155 def 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)