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104 lines
3.7 KiB
ReStructuredText
104 lines
3.7 KiB
ReStructuredText
:mod:`termios` --- POSIX style tty control
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==========================================
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.. module:: termios
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:platform: Unix
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:synopsis: POSIX style tty control.
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.. index::
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pair: POSIX; I/O control
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pair: tty; I/O control
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This module provides an interface to the POSIX calls for tty I/O control. For a
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complete description of these calls, see the POSIX or Unix manual pages. It is
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only available for those Unix versions that support POSIX *termios* style tty
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I/O control (and then only if configured at installation time).
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All functions in this module take a file descriptor *fd* as their first
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argument. This can be an integer file descriptor, such as returned by
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``sys.stdin.fileno()``, or a :term:`file object`, such as ``sys.stdin`` itself.
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This module also defines all the constants needed to work with the functions
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provided here; these have the same name as their counterparts in C. Please
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refer to your system documentation for more information on using these terminal
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control interfaces.
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The module defines the following functions:
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.. function:: tcgetattr(fd)
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Return a list containing the tty attributes for file descriptor *fd*, as
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follows: ``[iflag, oflag, cflag, lflag, ispeed, ospeed, cc]`` where *cc* is a
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list of the tty special characters (each a string of length 1, except the
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items with indices :const:`VMIN` and :const:`VTIME`, which are integers when
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these fields are defined). The interpretation of the flags and the speeds as
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well as the indexing in the *cc* array must be done using the symbolic
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constants defined in the :mod:`termios` module.
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.. function:: tcsetattr(fd, when, attributes)
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Set the tty attributes for file descriptor *fd* from the *attributes*, which is
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a list like the one returned by :func:`tcgetattr`. The *when* argument
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determines when the attributes are changed: :const:`TCSANOW` to change
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immediately, :const:`TCSADRAIN` to change after transmitting all queued output,
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or :const:`TCSAFLUSH` to change after transmitting all queued output and
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discarding all queued input.
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.. function:: tcsendbreak(fd, duration)
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Send a break on file descriptor *fd*. A zero *duration* sends a break for 0.25
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--0.5 seconds; a nonzero *duration* has a system dependent meaning.
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.. function:: tcdrain(fd)
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Wait until all output written to file descriptor *fd* has been transmitted.
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.. function:: tcflush(fd, queue)
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Discard queued data on file descriptor *fd*. The *queue* selector specifies
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which queue: :const:`TCIFLUSH` for the input queue, :const:`TCOFLUSH` for the
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output queue, or :const:`TCIOFLUSH` for both queues.
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.. function:: tcflow(fd, action)
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Suspend or resume input or output on file descriptor *fd*. The *action*
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argument can be :const:`TCOOFF` to suspend output, :const:`TCOON` to restart
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output, :const:`TCIOFF` to suspend input, or :const:`TCION` to restart input.
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.. seealso::
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Module :mod:`tty`
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Convenience functions for common terminal control operations.
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.. _termios-example:
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Example
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-------
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Here's a function that prompts for a password with echoing turned off. Note the
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technique using a separate :func:`tcgetattr` call and a :keyword:`try` ...
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:keyword:`finally` statement to ensure that the old tty attributes are restored
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exactly no matter what happens::
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def getpass(prompt="Password: "):
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import termios, sys
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fd = sys.stdin.fileno()
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old = termios.tcgetattr(fd)
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new = termios.tcgetattr(fd)
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new[3] = new[3] & ~termios.ECHO # lflags
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try:
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termios.tcsetattr(fd, termios.TCSADRAIN, new)
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passwd = input(prompt)
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finally:
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termios.tcsetattr(fd, termios.TCSADRAIN, old)
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return passwd
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