Doc/libtermios.tex

   1 \section{Built-in Module \sectcode{termios}}
   2 \bimodindex{termios}
   3 \indexii{Posix}{I/O control}
   4 \indexii{tty}{I/O control}
   5
   6 \renewcommand{\indexsubitem}{(in module termios)}
   7
   8 This module provides an interface to the Posix calls for tty I/O
   9 control.  For a complete description of these calls, see the Posix or
  10 \UNIX{} manual pages.  It is only available for those \UNIX{} versions
  11 that support Posix \code{termios} style tty I/O control (and then
  12 only if configured at installation time).
  13
  14 All functions in this module take a file descriptor \var{fd} as their
  15 first argument.  This must be an integer file descriptor, such as
  16 returned by \code{sys.stdin.fileno()}.
  17
  18 This module should be used in conjunction with the \code{TERMIOS}
  19 module, which defines the relevant symbolic constants (see the next
  20 section).
  21
  22 The module defines the following functions:
  23
  24 \begin{funcdesc}{tcgetattr}{fd}
  25 Return a list containing the tty attributes for file descriptor
  26 \var{fd}, as follows: \code{[\var{iflag}, \var{oflag}, \var{cflag},
  27 \var{lflag}, \var{ispeed}, \var{ospeed}, \var{cc}]} where \var{cc} is
  28 a list of the tty special characters (each a string of length 1,
  29 except the items with indices \code{VMIN} and \code{VTIME}, which are
  30 integers when these fields are defined).  The interpretation of the
  31 flags and the speeds as well as the indexing in the \var{cc} array
  32 must be done using the symbolic constants defined in the
  33 \code{TERMIOS} module.
  34 \end{funcdesc}
  35
  36 \begin{funcdesc}{tcsetattr}{fd\, when\, attributes}
  37 Set the tty attributes for file descriptor \var{fd} from the
  38 \var{attributes}, which is a list like the one returned by
  39 \code{tcgetattr()}.  The \var{when} argument determines when the
  40 attributes are changed: \code{TERMIOS.TCSANOW} to change immediately,
  41 \code{TERMIOS.TCSADRAIN} to change after transmitting all queued
  42 output, or \code{TERMIOS.TCSAFLUSH} to change after transmitting all
  43 queued output and discarding all queued input.
  44 \end{funcdesc}
  45
  46 \begin{funcdesc}{tcsendbreak}{fd\, duration}
  47 Send a break on file descriptor \var{fd}.  A zero \var{duration} sends
  48 a break for 0.25--0.5 seconds; a nonzero \var{duration} has a system
  49 dependent meaning.
  50 \end{funcdesc}
  51
  52 \begin{funcdesc}{tcdrain}{fd}
  53 Wait until all output written to file descriptor \var{fd} has been
  54 transmitted.
  55 \end{funcdesc}
  56
  57 \begin{funcdesc}{tcflush}{fd\, queue}
  58 Discard queued data on file descriptor \var{fd}.  The \var{queue}
  59 selector specifies which queue: \code{TERMIOS.TCIFLUSH} for the input
  60 queue, \code{TERMIOS.TCOFLUSH} for the output queue, or
  61 \code{TERMIOS.TCIOFLUSH} for both queues.
  62 \end{funcdesc}
  63
  64 \begin{funcdesc}{tcflow}{fd\, action}
  65 Suspend or resume input or output on file descriptor \var{fd}.  The
  66 \var{action} argument can be \code{TERMIOS.TCOOFF} to suspend output,
  67 \code{TERMIOS.TCOON} to restart output, \code{TERMIOS.TCIOFF} to
  68 suspend input, or \code{TERMIOS.TCION} to restart input.
  69 \end{funcdesc}
  70
  71 \subsection{Example}
  72 \nodename{termios Example}
  73
  74 Here's a function that prompts for a password with echoing turned off.
  75 Note the technique using a separate \code{termios.tcgetattr()} call
  76 and a \code{try {\ldots} finally} statement to ensure that the old tty
  77 attributes are restored exactly no matter what happens:
  78
  79 \begin{verbatim}
  80 def getpass(prompt = "Password: "):
  81     import termios, TERMIOS, sys
  82     fd = sys.stdin.fileno()
  83     old = termios.tcgetattr(fd)
  84     new = termios.tcgetattr(fd)
  85     new[3] = new[3] & ~TERMIOS.ECHO          # lflags
  86     try:
  87         termios.tcsetattr(fd, TERMIOS.TCSADRAIN, new)
  88         passwd = raw_input(prompt)
  89     finally:
  90         termios.tcsetattr(fd, TERMIOS.TCSADRAIN, old)
  91     return passwd
  92 \end{verbatim}
  93
  94
  95 \section{Standard Module \sectcode{TERMIOS}}
  96 \stmodindex{TERMIOS}
  97 \indexii{Posix}{I/O control}
  98 \indexii{tty}{I/O control}
  99
 100 \renewcommand{\indexsubitem}{(in module TERMIOS)}
 101
 102 This module defines the symbolic constants required to use the
 103 \code{termios} module (see the previous section).  See the Posix or
 104 \UNIX{} manual pages (or the source) for a list of those constants.
 105
 106 Note: this module resides in a system-dependent subdirectory of the
 107 Python library directory.  You may have to generate it for your
 108 particular system using the script \file{Tools/scripts/h2py.py}.