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, FCNTL
  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(FCNTL.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, FCNTL.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     return os.open(tty_name, FCNTL.O_RDWR)
  79
  80 def fork():
  81     """fork() -> (pid, master_fd)
  82     Fork and make the child a session leader with a controlling terminal."""
  83
  84     try:
  85         pid, fd = os.forkpty()
  86     except (AttributeError, OSError):
  87         pass
  88     else:
  89         if pid == CHILD:
  90             try:
  91                 os.setsid()
  92             except OSError:
  93                 # os.forkpty() already set us session leader
  94                 pass
  95         return pid, fd
  96
  97     master_fd, slave_fd = openpty()
  98     pid = os.fork()
  99     if pid == CHILD:
 100         # Establish a new session.
 101         os.setsid()
 102         os.close(master_fd)
 103
 104         # Slave becomes stdin/stdout/stderr of child.
 105         os.dup2(slave_fd, STDIN_FILENO)
 106         os.dup2(slave_fd, STDOUT_FILENO)
 107         os.dup2(slave_fd, STDERR_FILENO)
 108         if (slave_fd > STDERR_FILENO):
 109             os.close (slave_fd)
 110
 111     # Parent and child process.
 112     return pid, master_fd
 113
 114 def _writen(fd, data):
 115     """Write all the data to a descriptor."""
 116     while data != '':
 117         n = os.write(fd, data)
 118         data = data[n:]
 119
 120 def _read(fd):
 121     """Default read function."""
 122     return os.read(fd, 1024)
 123
 124 def _copy(master_fd, master_read=_read, stdin_read=_read):
 125     """Parent copy loop.
 126     Copies
 127             pty master -> standard output   (master_read)
 128             standard input -> pty master    (stdin_read)"""
 129     while 1:
 130         rfds, wfds, xfds = select(
 131                 [master_fd, STDIN_FILENO], [], [])
 132         if master_fd in rfds:
 133             data = master_read(master_fd)
 134             os.write(STDOUT_FILENO, data)
 135         if STDIN_FILENO in rfds:
 136             data = stdin_read(STDIN_FILENO)
 137             _writen(master_fd, data)
 138
 139 def spawn(argv, master_read=_read, stdin_read=_read):
 140     """Create a spawned process."""
 141     if type(argv) == type(''):
 142         argv = (argv,)
 143     pid, master_fd = fork()
 144     if pid == CHILD:
 145         apply(os.execlp, (argv[0],) + argv)
 146     mode = tty.tcgetattr(STDIN_FILENO)
 147     tty.setraw(STDIN_FILENO)
 148     try:
 149         _copy(master_fd, master_read, stdin_read)
 150     except:
 151         tty.tcsetattr(STDIN_FILENO, tty.TCSAFLUSH, mode)