1 2 :mod:`termios` --- POSIX style tty control 3 ========================================== 4 5 .. module:: termios 6 :platform: Unix 7 :synopsis: POSIX style tty control. 8 9 10 .. index:: 11 pair: POSIX; I/O control 12 pair: tty; I/O control 13 14 This module provides an interface to the POSIX calls for tty I/O control. For a 15 complete description of these calls, see :manpage:`termios(2)` Unix manual 16 page. It is only available for those Unix versions that support POSIX 17 *termios* style tty I/O control configured during installation. 18 19 All functions in this module take a file descriptor *fd* as their first 20 argument. This can be an integer file descriptor, such as returned by 21 ``sys.stdin.fileno()``, or a file object, such as ``sys.stdin`` itself. 22 23 This module also defines all the constants needed to work with the functions 24 provided here; these have the same name as their counterparts in C. Please 25 refer to your system documentation for more information on using these terminal 26 control interfaces. 27 28 The module defines the following functions: 29 30 31 .. function:: tcgetattr(fd) 32 33 Return a list containing the tty attributes for file descriptor *fd*, as 34 follows: ``[iflag, oflag, cflag, lflag, ispeed, ospeed, cc]`` where *cc* is a 35 list of the tty special characters (each a string of length 1, except the 36 items with indices :const:`VMIN` and :const:`VTIME`, which are integers when 37 these fields are defined). The interpretation of the flags and the speeds as 38 well as the indexing in the *cc* array must be done using the symbolic 39 constants defined in the :mod:`termios` module. 40 41 42 .. function:: tcsetattr(fd, when, attributes) 43 44 Set the tty attributes for file descriptor *fd* from the *attributes*, which is 45 a list like the one returned by :func:`tcgetattr`. The *when* argument 46 determines when the attributes are changed: :const:`TCSANOW` to change 47 immediately, :const:`TCSADRAIN` to change after transmitting all queued output, 48 or :const:`TCSAFLUSH` to change after transmitting all queued output and 49 discarding all queued input. 50 51 52 .. function:: tcsendbreak(fd, duration) 53 54 Send a break on file descriptor *fd*. A zero *duration* sends a break for 0.25 55 --0.5 seconds; a nonzero *duration* has a system dependent meaning. 56 57 58 .. function:: tcdrain(fd) 59 60 Wait until all output written to file descriptor *fd* has been transmitted. 61 62 63 .. function:: tcflush(fd, queue) 64 65 Discard queued data on file descriptor *fd*. The *queue* selector specifies 66 which queue: :const:`TCIFLUSH` for the input queue, :const:`TCOFLUSH` for the 67 output queue, or :const:`TCIOFLUSH` for both queues. 68 69 70 .. function:: tcflow(fd, action) 71 72 Suspend or resume input or output on file descriptor *fd*. The *action* 73 argument can be :const:`TCOOFF` to suspend output, :const:`TCOON` to restart 74 output, :const:`TCIOFF` to suspend input, or :const:`TCION` to restart input. 75 76 77 .. seealso:: 78 79 Module :mod:`tty` 80 Convenience functions for common terminal control operations. 81 82 83 Example 84 ------- 85 86 .. _termios-example: 87 88 Here's a function that prompts for a password with echoing turned off. Note the 89 technique using a separate :func:`tcgetattr` call and a :keyword:`try` ... 90 :keyword:`finally` statement to ensure that the old tty attributes are restored 91 exactly no matter what happens:: 92 93 def getpass(prompt="Password: "): 94 import termios, sys 95 fd = sys.stdin.fileno() 96 old = termios.tcgetattr(fd) 97 new = termios.tcgetattr(fd) 98 new[3] = new[3] & ~termios.ECHO # lflags 99 try: 100 termios.tcsetattr(fd, termios.TCSADRAIN, new) 101 passwd = raw_input(prompt) 102 finally: 103 termios.tcsetattr(fd, termios.TCSADRAIN, old) 104 return passwd 105 106
