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<div class="section" id="module-termios">
<span id="termios-posix-style-tty-control"></span><h1>35.6. <a class="reference internal" href="#module-termios" title="termios: POSIX style tty control. (Unix)"><code class="xref py py-mod docutils literal"><span class="pre">termios</span></code></a> — POSIX style tty control<a class="headerlink" href="#module-termios" title="Permalink to this headline">¶</a></h1>
<hr class="docutils" id="index-0" />
<p>This module provides an interface to the POSIX calls for tty I/O control. For a
complete description of these calls, see <em class="manpage">termios(2)</em> Unix manual
page. It is only available for those Unix versions that support POSIX
<em>termios</em> style tty I/O control configured during installation.</p>
<p>All functions in this module take a file descriptor <em>fd</em> as their first
argument. This can be an integer file descriptor, such as returned by
<code class="docutils literal"><span class="pre">sys.stdin.fileno()</span></code>, or a <a class="reference internal" href="../glossary.html#term-file-object"><span class="xref std std-term">file object</span></a>, such as <code class="docutils literal"><span class="pre">sys.stdin</span></code> itself.</p>
<p>This module also defines all the constants needed to work with the functions
provided here; these have the same name as their counterparts in C. Please
refer to your system documentation for more information on using these terminal
control interfaces.</p>
<p>The module defines the following functions:</p>
<dl class="function">
<dt id="termios.tcgetattr">
<code class="descclassname">termios.</code><code class="descname">tcgetattr</code><span class="sig-paren">(</span><em>fd</em><span class="sig-paren">)</span><a class="headerlink" href="#termios.tcgetattr" title="Permalink to this definition">¶</a></dt>
<dd><p>Return a list containing the tty attributes for file descriptor <em>fd</em>, as
follows: <code class="docutils literal"><span class="pre">[iflag,</span> <span class="pre">oflag,</span> <span class="pre">cflag,</span> <span class="pre">lflag,</span> <span class="pre">ispeed,</span> <span class="pre">ospeed,</span> <span class="pre">cc]</span></code> where <em>cc</em> is a
list of the tty special characters (each a string of length 1, except the
items with indices <code class="xref py py-const docutils literal"><span class="pre">VMIN</span></code> and <code class="xref py py-const docutils literal"><span class="pre">VTIME</span></code>, which are integers when
these fields are defined). The interpretation of the flags and the speeds as
well as the indexing in the <em>cc</em> array must be done using the symbolic
constants defined in the <a class="reference internal" href="#module-termios" title="termios: POSIX style tty control. (Unix)"><code class="xref py py-mod docutils literal"><span class="pre">termios</span></code></a> module.</p>
</dd></dl>
<dl class="function">
<dt id="termios.tcsetattr">
<code class="descclassname">termios.</code><code class="descname">tcsetattr</code><span class="sig-paren">(</span><em>fd</em>, <em>when</em>, <em>attributes</em><span class="sig-paren">)</span><a class="headerlink" href="#termios.tcsetattr" title="Permalink to this definition">¶</a></dt>
<dd><p>Set the tty attributes for file descriptor <em>fd</em> from the <em>attributes</em>, which is
a list like the one returned by <a class="reference internal" href="#termios.tcgetattr" title="termios.tcgetattr"><code class="xref py py-func docutils literal"><span class="pre">tcgetattr()</span></code></a>. The <em>when</em> argument
determines when the attributes are changed: <code class="xref py py-const docutils literal"><span class="pre">TCSANOW</span></code> to change
immediately, <code class="xref py py-const docutils literal"><span class="pre">TCSADRAIN</span></code> to change after transmitting all queued output,
or <code class="xref py py-const docutils literal"><span class="pre">TCSAFLUSH</span></code> to change after transmitting all queued output and
discarding all queued input.</p>
</dd></dl>
<dl class="function">
<dt id="termios.tcsendbreak">
<code class="descclassname">termios.</code><code class="descname">tcsendbreak</code><span class="sig-paren">(</span><em>fd</em>, <em>duration</em><span class="sig-paren">)</span><a class="headerlink" href="#termios.tcsendbreak" title="Permalink to this definition">¶</a></dt>
<dd><p>Send a break on file descriptor <em>fd</em>. A zero <em>duration</em> sends a break for 0.25
–0.5 seconds; a nonzero <em>duration</em> has a system dependent meaning.</p>
</dd></dl>
<dl class="function">
<dt id="termios.tcdrain">
<code class="descclassname">termios.</code><code class="descname">tcdrain</code><span class="sig-paren">(</span><em>fd</em><span class="sig-paren">)</span><a class="headerlink" href="#termios.tcdrain" title="Permalink to this definition">¶</a></dt>
<dd><p>Wait until all output written to file descriptor <em>fd</em> has been transmitted.</p>
</dd></dl>
<dl class="function">
<dt id="termios.tcflush">
<code class="descclassname">termios.</code><code class="descname">tcflush</code><span class="sig-paren">(</span><em>fd</em>, <em>queue</em><span class="sig-paren">)</span><a class="headerlink" href="#termios.tcflush" title="Permalink to this definition">¶</a></dt>
<dd><p>Discard queued data on file descriptor <em>fd</em>. The <em>queue</em> selector specifies
which queue: <code class="xref py py-const docutils literal"><span class="pre">TCIFLUSH</span></code> for the input queue, <code class="xref py py-const docutils literal"><span class="pre">TCOFLUSH</span></code> for the
output queue, or <code class="xref py py-const docutils literal"><span class="pre">TCIOFLUSH</span></code> for both queues.</p>
</dd></dl>
<dl class="function">
<dt id="termios.tcflow">
<code class="descclassname">termios.</code><code class="descname">tcflow</code><span class="sig-paren">(</span><em>fd</em>, <em>action</em><span class="sig-paren">)</span><a class="headerlink" href="#termios.tcflow" title="Permalink to this definition">¶</a></dt>
<dd><p>Suspend or resume input or output on file descriptor <em>fd</em>. The <em>action</em>
argument can be <code class="xref py py-const docutils literal"><span class="pre">TCOOFF</span></code> to suspend output, <code class="xref py py-const docutils literal"><span class="pre">TCOON</span></code> to restart
output, <code class="xref py py-const docutils literal"><span class="pre">TCIOFF</span></code> to suspend input, or <code class="xref py py-const docutils literal"><span class="pre">TCION</span></code> to restart input.</p>
</dd></dl>
<div class="admonition seealso">
<p class="first admonition-title">See also</p>
<dl class="last docutils">
<dt>Module <a class="reference internal" href="tty.html#module-tty" title="tty: Utility functions that perform common terminal control operations. (Unix)"><code class="xref py py-mod docutils literal"><span class="pre">tty</span></code></a></dt>
<dd>Convenience functions for common terminal control operations.</dd>
</dl>
</div>
<div class="section" id="example">
<span id="termios-example"></span><h2>35.6.1. Example<a class="headerlink" href="#example" title="Permalink to this headline">¶</a></h2>
<p>Here’s a function that prompts for a password with echoing turned off. Note the
technique using a separate <a class="reference internal" href="#termios.tcgetattr" title="termios.tcgetattr"><code class="xref py py-func docutils literal"><span class="pre">tcgetattr()</span></code></a> call and a <a class="reference internal" href="../reference/compound_stmts.html#try"><code class="xref std std-keyword docutils literal"><span class="pre">try</span></code></a> ...
<a class="reference internal" href="../reference/compound_stmts.html#finally"><code class="xref std std-keyword docutils literal"><span class="pre">finally</span></code></a> statement to ensure that the old tty attributes are restored
exactly no matter what happens:</p>
<div class="highlight-python3"><div class="highlight"><pre><span></span><span class="k">def</span> <span class="nf">getpass</span><span class="p">(</span><span class="n">prompt</span><span class="o">=</span><span class="s2">"Password: "</span><span class="p">):</span>
<span class="kn">import</span> <span class="nn">termios</span><span class="o">,</span> <span class="nn">sys</span>
<span class="n">fd</span> <span class="o">=</span> <span class="n">sys</span><span class="o">.</span><span class="n">stdin</span><span class="o">.</span><span class="n">fileno</span><span class="p">()</span>
<span class="n">old</span> <span class="o">=</span> <span class="n">termios</span><span class="o">.</span><span class="n">tcgetattr</span><span class="p">(</span><span class="n">fd</span><span class="p">)</span>
<span class="n">new</span> <span class="o">=</span> <span class="n">termios</span><span class="o">.</span><span class="n">tcgetattr</span><span class="p">(</span><span class="n">fd</span><span class="p">)</span>
<span class="n">new</span><span class="p">[</span><span class="mi">3</span><span class="p">]</span> <span class="o">=</span> <span class="n">new</span><span class="p">[</span><span class="mi">3</span><span class="p">]</span> <span class="o">&</span> <span class="o">~</span><span class="n">termios</span><span class="o">.</span><span class="n">ECHO</span> <span class="c1"># lflags</span>
<span class="k">try</span><span class="p">:</span>
<span class="n">termios</span><span class="o">.</span><span class="n">tcsetattr</span><span class="p">(</span><span class="n">fd</span><span class="p">,</span> <span class="n">termios</span><span class="o">.</span><span class="n">TCSADRAIN</span><span class="p">,</span> <span class="n">new</span><span class="p">)</span>
<span class="n">passwd</span> <span class="o">=</span> <span class="nb">input</span><span class="p">(</span><span class="n">prompt</span><span class="p">)</span>
<span class="k">finally</span><span class="p">:</span>
<span class="n">termios</span><span class="o">.</span><span class="n">tcsetattr</span><span class="p">(</span><span class="n">fd</span><span class="p">,</span> <span class="n">termios</span><span class="o">.</span><span class="n">TCSADRAIN</span><span class="p">,</span> <span class="n">old</span><span class="p">)</span>
<span class="k">return</span> <span class="n">passwd</span>
</pre></div>
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<h3><a href="../contents.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">35.6. <code class="docutils literal"><span class="pre">termios</span></code> — POSIX style tty control</a><ul>
<li><a class="reference internal" href="#example">35.6.1. Example</a></li>
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<h4>Previous topic</h4>
<p class="topless"><a href="crypt.html"
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<h4>Next topic</h4>
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