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 STDIN_FILENO = 0
  14 STDOUT_FILENO = 1
  15 STDERR_FILENO = 2
  16
  17 CHILD = 0
  18
  19 def openpty():
  20         """openpty() -> (master_fd, slave_fd)
  21         Open a pty master/slave pair, using os.openpty() if possible."""
  22
  23         try:
  24                 return os.openpty()
  25         except (AttributeError, OSError):
  26                 pass
  27         master_fd, slave_name = _open_terminal()
  28         slave_fd = slave_open(slave_name)
  29         return master_fd, slave_fd
  30
  31 def master_open():
  32         """master_open() -> (master_fd, slave_name)
  33         Open a pty master and return the fd, and the filename of the slave end.
  34         Deprecated, use openpty() instead."""
  35
  36         try:
  37                 master_fd, slave_fd = os.openpty()
  38         except (AttributeError, OSError):
  39                 pass
  40         else:
  41                 slave_name = os.ttyname(slave_fd)
  42                 os.close(slave_fd)
  43                 return master_fd, slave_name
  44
  45         return _open_terminal()
  46
  47 def _open_terminal():
  48         """Open pty master and return (master_fd, tty_name).
  49         SGI and generic BSD version, for when openpty() fails."""
  50         try:
  51                 import sgi
  52         except ImportError:
  53                 pass
  54         else:
  55                 try:
  56                     tty_name, master_fd = sgi._getpty(FCNTL.O_RDWR, 0666, 0)
  57                 except IOError, msg:
  58                         raise os.error, msg
  59                 return master_fd, tty_name
  60         for x in 'pqrstuvwxyzPQRST':
  61                 for y in '0123456789abcdef':
  62                         pty_name = '/dev/pty' + x + y
  63                         try:
  64                                 fd = os.open(pty_name, FCNTL.O_RDWR)
  65                         except os.error:
  66                                 continue
  67                         return (fd, '/dev/tty' + x + y)
  68         raise os.error, 'out of pty devices'
  69
  70 def slave_open(tty_name):
  71         """slave_open(tty_name) -> slave_fd
  72         Open the pty slave and acquire the controlling terminal, returning
  73         opened filedescriptor.
  74         Deprecated, use openpty() instead."""
  75
  76         return os.open(tty_name, FCNTL.O_RDWR)
  77
  78 def fork():
  79         """fork() -> (pid, master_fd)
  80         Fork and make the child a session leader with a controlling terminal."""
  81
  82         try:
  83                 pid, fd = os.forkpty()
  84         except (AttributeError, OSError):
  85                 pass
  86         else:
  87                 if pid == CHILD:
  88                         try:
  89                                 os.setsid()
  90                         except OSError:
  91                                 # os.forkpty() already set us session leader
  92                                 pass
  93                 return pid, fd
  94
  95         master_fd, slave_fd = openpty()
  96         pid = os.fork()
  97         if pid == CHILD:
  98                 # Establish a new session.
  99                 os.setsid()
 100                 os.close(master_fd)
 101
 102                 # Slave becomes stdin/stdout/stderr of child.
 103                 os.dup2(slave_fd, STDIN_FILENO)
 104                 os.dup2(slave_fd, STDOUT_FILENO)
 105                 os.dup2(slave_fd, STDERR_FILENO)
 106                 if (slave_fd > STDERR_FILENO):
 107                         os.close (slave_fd)
 108
 109         # Parent and child process.
 110         return pid, master_fd
 111
 112 def _writen(fd, data):
 113         """Write all the data to a descriptor."""
 114         while data != '':
 115                 n = os.write(fd, data)
 116                 data = data[n:]
 117
 118 def _read(fd):
 119         """Default read function."""
 120         return os.read(fd, 1024)
 121
 122 def _copy(master_fd, master_read=_read, stdin_read=_read):
 123         """Parent copy loop.
 124         Copies
 125                 pty master -> standard output   (master_read)
 126                 standard input -> pty master    (stdin_read)"""
 127         while 1:
 128                 rfds, wfds, xfds = select(
 129                         [master_fd, STDIN_FILENO], [], [])
 130                 if master_fd in rfds:
 131                         data = master_read(master_fd)
 132                         os.write(STDOUT_FILENO, data)
 133                 if STDIN_FILENO in rfds:
 134                         data = stdin_read(STDIN_FILENO)
 135                         _writen(master_fd, data)
 136
 137 def spawn(argv, master_read=_read, stdin_read=_read):
 138         """Create a spawned process."""
 139         if type(argv) == type(''):
 140                 argv = (argv,)
 141         pid, master_fd = fork()
 142         if pid == CHILD:
 143                 apply(os.execlp, (argv[0],) + argv)
 144         mode = tty.tcgetattr(STDIN_FILENO)
 145         tty.setraw(STDIN_FILENO)
 146         try:
 147                 _copy(master_fd, master_read, stdin_read)
 148         except:
 149                 tty.tcsetattr(STDIN_FILENO, tty.TCSAFLUSH, mode)