Lib/pty.py

   1 # pty.py -- 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, sys, FCNTL
  11 import tty
  12
  13 STDIN_FILENO = 0
  14 STDOUT_FILENO = 1
  15 STDERR_FILENO = 2
  16
  17 CHILD = 0
  18
  19 # Open pty master.  Returns (master_fd, tty_name).  SGI and Linux/BSD version.
  20 def master_open():
  21         try:
  22                 import sgi
  23         except ImportError:
  24                 pass
  25         else:
  26                 try:
  27                     tty_name, master_fd = sgi._getpty(FCNTL.O_RDWR, 0666, 0)
  28                 except IOError, msg:
  29                         raise os.error, msg
  30                 return master_fd, tty_name
  31         for x in 'pqrstuvwxyzPQRST':
  32                 for y in '0123456789abcdef':
  33                         pty_name = '/dev/pty' + x + y
  34                         try:
  35                                 fd = os.open(pty_name, FCNTL.O_RDWR)
  36                         except os.error:
  37                                 continue
  38                         return (fd, '/dev/tty' + x + y)
  39         raise os.error, 'out of pty devices'
  40
  41 # Open the pty slave.  Acquire the controlling terminal.
  42 # Returns file descriptor.  Linux version.  (Should be universal? --Guido)
  43 def slave_open(tty_name):
  44         return os.open(tty_name, FCNTL.O_RDWR)
  45
  46 # Fork and make the child a session leader with a controlling terminal.
  47 # Returns (pid, master_fd)
  48 def fork():
  49         master_fd, tty_name = master_open()
  50         pid = os.fork()
  51         if pid == CHILD:
  52                 # Establish a new session.
  53                 os.setsid()
  54
  55                 # Acquire controlling terminal.
  56                 slave_fd = slave_open(tty_name)
  57                 os.close(master_fd)
  58
  59                 # Slave becomes stdin/stdout/stderr of child.
  60                 os.dup2(slave_fd, STDIN_FILENO)
  61                 os.dup2(slave_fd, STDOUT_FILENO)
  62                 os.dup2(slave_fd, STDERR_FILENO)
  63                 if (slave_fd > STDERR_FILENO):
  64                         os.close (slave_fd)
  65
  66         # Parent and child process.
  67         return pid, master_fd
  68
  69 # Write all the data to a descriptor.
  70 def writen(fd, data):
  71         while data != '':
  72                 n = os.write(fd, data)
  73                 data = data[n:]
  74
  75 # Default read function.
  76 def read(fd):
  77         return os.read(fd, 1024)
  78
  79 # Parent copy loop.
  80 # Copies
  81 #       pty master -> standard output   (master_read)
  82 #       standard input -> pty master    (stdin_read)
  83 def copy(master_fd, master_read=read, stdin_read=read):
  84         while 1:
  85                 rfds, wfds, xfds = select(
  86                         [master_fd, STDIN_FILENO], [], [])
  87                 if master_fd in rfds:
  88                         data = master_read(master_fd)
  89                         os.write(STDOUT_FILENO, data)
  90                 if STDIN_FILENO in rfds:
  91                         data = stdin_read(STDIN_FILENO)
  92                         writen(master_fd, data)
  93
  94 # Create a spawned process.
  95 def spawn(argv, master_read=read, stdin_read=read):
  96         if type(argv) == type(''):
  97                 argv = (argv,)
  98         pid, master_fd = fork()
  99         if pid == CHILD:
 100                 apply(os.execlp, (argv[0],) + argv)
 101         mode = tty.tcgetattr(STDIN_FILENO)
 102         tty.setraw(STDIN_FILENO)
 103         try:
 104                 copy(master_fd, master_read, stdin_read)
 105         except:
 106                 tty.tcsetattr(STDIN_FILENO, tty.TCSAFLUSH, mode)