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<div class="section" id="module-msvcrt">
<h1>34.2. <tt class="xref docutils literal"><span class="pre">msvcrt</span></tt> – Useful routines from the MS VC++ runtime<a class="headerlink" href="#module-msvcrt" title="Permalink to this headline">¶</a></h1>
<p><em>Platforms: </em>Windows</p>
<p>These functions provide access to some useful capabilities on Windows platforms.
Some higher-level modules use these functions to build the Windows
implementations of their services. For example, the <a title="Portable reading of passwords and retrieval of the userid." class="reference external" href="getpass.html#module-getpass"><tt class="xref docutils literal"><span class="pre">getpass</span></tt></a> module uses
this in the implementation of the <tt class="xref docutils literal"><span class="pre">getpass()</span></tt> function.</p>
<p>Further documentation on these functions can be found in the Platform API
documentation.</p>
<p>The module implements both the normal and wide char variants of the console I/O
api. The normal API deals only with ASCII characters and is of limited use
for internationalized applications. The wide char API should be used where
ever possible</p>
<div class="section" id="file-operations">
<span id="msvcrt-files"></span><h2>34.2.1. File Operations<a class="headerlink" href="#file-operations" title="Permalink to this headline">¶</a></h2>
<dl class="function">
<dt id="msvcrt.locking">
<tt class="descclassname">msvcrt.</tt><tt class="descname">locking</tt><big>(</big><em>fd</em>, <em>mode</em>, <em>nbytes</em><big>)</big><a class="headerlink" href="#msvcrt.locking" title="Permalink to this definition">¶</a></dt>
<dd>Lock part of a file based on file descriptor <em>fd</em> from the C runtime. Raises
<a title="exceptions.IOError" class="reference external" href="exceptions.html#exceptions.IOError"><tt class="xref docutils literal"><span class="pre">IOError</span></tt></a> on failure. The locked region of the file extends from the
current file position for <em>nbytes</em> bytes, and may continue beyond the end of the
file. <em>mode</em> must be one of the <tt class="xref docutils literal"><span class="pre">LK_*</span></tt> constants listed below. Multiple
regions in a file may be locked at the same time, but may not overlap. Adjacent
regions are not merged; they must be unlocked individually.</dd></dl>
<dl class="data">
<dt id="msvcrt.LK_LOCK">
<tt class="descclassname">msvcrt.</tt><tt class="descname">LK_LOCK</tt><a class="headerlink" href="#msvcrt.LK_LOCK" title="Permalink to this definition">¶</a></dt>
<dt id="msvcrt.LK_RLCK">
<tt class="descclassname">msvcrt.</tt><tt class="descname">LK_RLCK</tt><a class="headerlink" href="#msvcrt.LK_RLCK" title="Permalink to this definition">¶</a></dt>
<dd>Locks the specified bytes. If the bytes cannot be locked, the program
immediately tries again after 1 second. If, after 10 attempts, the bytes cannot
be locked, <a title="exceptions.IOError" class="reference external" href="exceptions.html#exceptions.IOError"><tt class="xref docutils literal"><span class="pre">IOError</span></tt></a> is raised.</dd></dl>
<dl class="data">
<dt id="msvcrt.LK_NBLCK">
<tt class="descclassname">msvcrt.</tt><tt class="descname">LK_NBLCK</tt><a class="headerlink" href="#msvcrt.LK_NBLCK" title="Permalink to this definition">¶</a></dt>
<dt id="msvcrt.LK_NBRLCK">
<tt class="descclassname">msvcrt.</tt><tt class="descname">LK_NBRLCK</tt><a class="headerlink" href="#msvcrt.LK_NBRLCK" title="Permalink to this definition">¶</a></dt>
<dd>Locks the specified bytes. If the bytes cannot be locked, <a title="exceptions.IOError" class="reference external" href="exceptions.html#exceptions.IOError"><tt class="xref docutils literal"><span class="pre">IOError</span></tt></a> is
raised.</dd></dl>
<dl class="data">
<dt id="msvcrt.LK_UNLCK">
<tt class="descclassname">msvcrt.</tt><tt class="descname">LK_UNLCK</tt><a class="headerlink" href="#msvcrt.LK_UNLCK" title="Permalink to this definition">¶</a></dt>
<dd>Unlocks the specified bytes, which must have been previously locked.</dd></dl>
<dl class="function">
<dt id="msvcrt.setmode">
<tt class="descclassname">msvcrt.</tt><tt class="descname">setmode</tt><big>(</big><em>fd</em>, <em>flags</em><big>)</big><a class="headerlink" href="#msvcrt.setmode" title="Permalink to this definition">¶</a></dt>
<dd>Set the line-end translation mode for the file descriptor <em>fd</em>. To set it to
text mode, <em>flags</em> should be <a title="os.O_TEXT" class="reference external" href="os.html#os.O_TEXT"><tt class="xref docutils literal"><span class="pre">os.O_TEXT</span></tt></a>; for binary, it should be
<a title="os.O_BINARY" class="reference external" href="os.html#os.O_BINARY"><tt class="xref docutils literal"><span class="pre">os.O_BINARY</span></tt></a>.</dd></dl>
<dl class="function">
<dt id="msvcrt.open_osfhandle">
<tt class="descclassname">msvcrt.</tt><tt class="descname">open_osfhandle</tt><big>(</big><em>handle</em>, <em>flags</em><big>)</big><a class="headerlink" href="#msvcrt.open_osfhandle" title="Permalink to this definition">¶</a></dt>
<dd>Create a C runtime file descriptor from the file handle <em>handle</em>. The <em>flags</em>
parameter should be a bitwise OR of <a title="os.O_APPEND" class="reference external" href="os.html#os.O_APPEND"><tt class="xref docutils literal"><span class="pre">os.O_APPEND</span></tt></a>, <a title="os.O_RDONLY" class="reference external" href="os.html#os.O_RDONLY"><tt class="xref docutils literal"><span class="pre">os.O_RDONLY</span></tt></a>,
and <a title="os.O_TEXT" class="reference external" href="os.html#os.O_TEXT"><tt class="xref docutils literal"><span class="pre">os.O_TEXT</span></tt></a>. The returned file descriptor may be used as a parameter
to <a title="os.fdopen" class="reference external" href="os.html#os.fdopen"><tt class="xref docutils literal"><span class="pre">os.fdopen()</span></tt></a> to create a file object.</dd></dl>
<dl class="function">
<dt id="msvcrt.get_osfhandle">
<tt class="descclassname">msvcrt.</tt><tt class="descname">get_osfhandle</tt><big>(</big><em>fd</em><big>)</big><a class="headerlink" href="#msvcrt.get_osfhandle" title="Permalink to this definition">¶</a></dt>
<dd>Return the file handle for the file descriptor <em>fd</em>. Raises <a title="exceptions.IOError" class="reference external" href="exceptions.html#exceptions.IOError"><tt class="xref docutils literal"><span class="pre">IOError</span></tt></a> if
<em>fd</em> is not recognized.</dd></dl>
</div>
<div class="section" id="console-i-o">
<span id="msvcrt-console"></span><h2>34.2.2. Console I/O<a class="headerlink" href="#console-i-o" title="Permalink to this headline">¶</a></h2>
<dl class="function">
<dt id="msvcrt.kbhit">
<tt class="descclassname">msvcrt.</tt><tt class="descname">kbhit</tt><big>(</big><big>)</big><a class="headerlink" href="#msvcrt.kbhit" title="Permalink to this definition">¶</a></dt>
<dd>Return true if a keypress is waiting to be read.</dd></dl>
<dl class="function">
<dt id="msvcrt.getch">
<tt class="descclassname">msvcrt.</tt><tt class="descname">getch</tt><big>(</big><big>)</big><a class="headerlink" href="#msvcrt.getch" title="Permalink to this definition">¶</a></dt>
<dd>Read a keypress and return the resulting character. Nothing is echoed to the
console. This call will block if a keypress is not already available, but will
not wait for <tt class="docutils literal"><span class="pre">Enter</span></tt> to be pressed. If the pressed key was a special
function key, this will return <tt class="docutils literal"><span class="pre">'\000'</span></tt> or <tt class="docutils literal"><span class="pre">'\xe0'</span></tt>; the next call will
return the keycode. The <tt class="docutils literal"><span class="pre">Control-C</span></tt> keypress cannot be read with this
function.</dd></dl>
<dl class="function">
<dt id="msvcrt.getwch">
<tt class="descclassname">msvcrt.</tt><tt class="descname">getwch</tt><big>(</big><big>)</big><a class="headerlink" href="#msvcrt.getwch" title="Permalink to this definition">¶</a></dt>
<dd><p>Wide char variant of <a title="msvcrt.getch" class="reference internal" href="#msvcrt.getch"><tt class="xref docutils literal"><span class="pre">getch()</span></tt></a>, returning a Unicode value.</p>
<p class="versionadded">
<span class="versionmodified">New in version 2.6.</span></p>
</dd></dl>
<dl class="function">
<dt id="msvcrt.getche">
<tt class="descclassname">msvcrt.</tt><tt class="descname">getche</tt><big>(</big><big>)</big><a class="headerlink" href="#msvcrt.getche" title="Permalink to this definition">¶</a></dt>
<dd>Similar to <a title="msvcrt.getch" class="reference internal" href="#msvcrt.getch"><tt class="xref docutils literal"><span class="pre">getch()</span></tt></a>, but the keypress will be echoed if it represents a
printable character.</dd></dl>
<dl class="function">
<dt id="msvcrt.getwche">
<tt class="descclassname">msvcrt.</tt><tt class="descname">getwche</tt><big>(</big><big>)</big><a class="headerlink" href="#msvcrt.getwche" title="Permalink to this definition">¶</a></dt>
<dd><p>Wide char variant of <a title="msvcrt.getche" class="reference internal" href="#msvcrt.getche"><tt class="xref docutils literal"><span class="pre">getche()</span></tt></a>, returning a Unicode value.</p>
<p class="versionadded">
<span class="versionmodified">New in version 2.6.</span></p>
</dd></dl>
<dl class="function">
<dt id="msvcrt.putch">
<tt class="descclassname">msvcrt.</tt><tt class="descname">putch</tt><big>(</big><em>char</em><big>)</big><a class="headerlink" href="#msvcrt.putch" title="Permalink to this definition">¶</a></dt>
<dd>Print the character <em>char</em> to the console without buffering.</dd></dl>
<dl class="function">
<dt id="msvcrt.putwch">
<tt class="descclassname">msvcrt.</tt><tt class="descname">putwch</tt><big>(</big><em>unicode_char</em><big>)</big><a class="headerlink" href="#msvcrt.putwch" title="Permalink to this definition">¶</a></dt>
<dd><p>Wide char variant of <a title="msvcrt.putch" class="reference internal" href="#msvcrt.putch"><tt class="xref docutils literal"><span class="pre">putch()</span></tt></a>, accepting a Unicode value.</p>
<p class="versionadded">
<span class="versionmodified">New in version 2.6.</span></p>
</dd></dl>
<dl class="function">
<dt id="msvcrt.ungetch">
<tt class="descclassname">msvcrt.</tt><tt class="descname">ungetch</tt><big>(</big><em>char</em><big>)</big><a class="headerlink" href="#msvcrt.ungetch" title="Permalink to this definition">¶</a></dt>
<dd>Cause the character <em>char</em> to be “pushed back” into the console buffer; it will
be the next character read by <a title="msvcrt.getch" class="reference internal" href="#msvcrt.getch"><tt class="xref docutils literal"><span class="pre">getch()</span></tt></a> or <a title="msvcrt.getche" class="reference internal" href="#msvcrt.getche"><tt class="xref docutils literal"><span class="pre">getche()</span></tt></a>.</dd></dl>
<dl class="function">
<dt id="msvcrt.ungetwch">
<tt class="descclassname">msvcrt.</tt><tt class="descname">ungetwch</tt><big>(</big><em>unicode_char</em><big>)</big><a class="headerlink" href="#msvcrt.ungetwch" title="Permalink to this definition">¶</a></dt>
<dd><p>Wide char variant of <a title="msvcrt.ungetch" class="reference internal" href="#msvcrt.ungetch"><tt class="xref docutils literal"><span class="pre">ungetch()</span></tt></a>, accepting a Unicode value.</p>
<p class="versionadded">
<span class="versionmodified">New in version 2.6.</span></p>
</dd></dl>
</div>
<div class="section" id="other-functions">
<span id="msvcrt-other"></span><h2>34.2.3. Other Functions<a class="headerlink" href="#other-functions" title="Permalink to this headline">¶</a></h2>
<dl class="function">
<dt id="msvcrt.heapmin">
<tt class="descclassname">msvcrt.</tt><tt class="descname">heapmin</tt><big>(</big><big>)</big><a class="headerlink" href="#msvcrt.heapmin" title="Permalink to this definition">¶</a></dt>
<dd>Force the <tt class="xref docutils literal"><span class="pre">malloc()</span></tt> heap to clean itself up and return unused blocks to
the operating system. On failure, this raises <a title="exceptions.IOError" class="reference external" href="exceptions.html#exceptions.IOError"><tt class="xref docutils literal"><span class="pre">IOError</span></tt></a>.</dd></dl>
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<h3><a href="../contents.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference external" href="#">34.2. <tt class="docutils literal"><span class="pre">msvcrt</span></tt> – Useful routines from the MS VC++ runtime</a><ul>
<li><a class="reference external" href="#file-operations">34.2.1. File Operations</a></li>
<li><a class="reference external" href="#console-i-o">34.2.2. Console I/O</a></li>
<li><a class="reference external" href="#other-functions">34.2.3. Other Functions</a></li>
</ul>
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