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<div class="section" id="module-select">
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<span id="select-waiting-for-i-o-completion"></span><h1><a class="reference internal" href="#module-select" title="select: Wait for I/O completion on multiple streams."><code class="xref py py-mod docutils literal notranslate"><span class="pre">select</span></code></a> — Waiting for I/O completion<a class="headerlink" href="#module-select" title="Permalink to this headline">¶</a></h1>
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<hr class="docutils" />
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<p>This module provides access to the <code class="xref c c-func docutils literal notranslate"><span class="pre">select()</span></code> and <code class="xref c c-func docutils literal notranslate"><span class="pre">poll()</span></code> functions
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available in most operating systems, <code class="xref c c-func docutils literal notranslate"><span class="pre">devpoll()</span></code> available on
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Solaris and derivatives, <code class="xref c c-func docutils literal notranslate"><span class="pre">epoll()</span></code> available on Linux 2.5+ and
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<code class="xref c c-func docutils literal notranslate"><span class="pre">kqueue()</span></code> available on most BSD.
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Note that on Windows, it only works for sockets; on other operating systems,
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it also works for other file types (in particular, on Unix, it works on pipes).
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It cannot be used on regular files to determine whether a file has grown since
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it was last read.</p>
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<div class="admonition note">
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<p class="admonition-title">Note</p>
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<p>The <a class="reference internal" href="selectors.html#module-selectors" title="selectors: High-level I/O multiplexing."><code class="xref py py-mod docutils literal notranslate"><span class="pre">selectors</span></code></a> module allows high-level and efficient I/O
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multiplexing, built upon the <a class="reference internal" href="#module-select" title="select: Wait for I/O completion on multiple streams."><code class="xref py py-mod docutils literal notranslate"><span class="pre">select</span></code></a> module primitives. Users are
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encouraged to use the <a class="reference internal" href="selectors.html#module-selectors" title="selectors: High-level I/O multiplexing."><code class="xref py py-mod docutils literal notranslate"><span class="pre">selectors</span></code></a> module instead, unless they want
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precise control over the OS-level primitives used.</p>
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</div>
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<p>The module defines the following:</p>
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<dl class="exception">
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<dt id="select.error">
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<em class="property">exception </em><code class="descclassname">select.</code><code class="descname">error</code><a class="headerlink" href="#select.error" title="Permalink to this definition">¶</a></dt>
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<dd><p>A deprecated alias of <a class="reference internal" href="exceptions.html#OSError" title="OSError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">OSError</span></code></a>.</p>
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<div class="versionchanged">
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<p><span class="versionmodified changed">Changed in version 3.3: </span>Following <span class="target" id="index-0"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-3151"><strong>PEP 3151</strong></a>, this class was made an alias of <a class="reference internal" href="exceptions.html#OSError" title="OSError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">OSError</span></code></a>.</p>
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</div>
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</dd></dl>
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<dl class="function">
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<dt id="select.devpoll">
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<code class="descclassname">select.</code><code class="descname">devpoll</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#select.devpoll" title="Permalink to this definition">¶</a></dt>
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<dd><p>(Only supported on Solaris and derivatives.) Returns a <code class="docutils literal notranslate"><span class="pre">/dev/poll</span></code>
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polling object; see section <a class="reference internal" href="#devpoll-objects"><span class="std std-ref">/dev/poll Polling Objects</span></a> below for the
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methods supported by devpoll objects.</p>
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<p><code class="xref c c-func docutils literal notranslate"><span class="pre">devpoll()</span></code> objects are linked to the number of file
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descriptors allowed at the time of instantiation. If your program
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reduces this value, <code class="xref c c-func docutils literal notranslate"><span class="pre">devpoll()</span></code> will fail. If your program
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increases this value, <code class="xref c c-func docutils literal notranslate"><span class="pre">devpoll()</span></code> may return an
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incomplete list of active file descriptors.</p>
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<p>The new file descriptor is <a class="reference internal" href="os.html#fd-inheritance"><span class="std std-ref">non-inheritable</span></a>.</p>
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<div class="versionadded">
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<p><span class="versionmodified added">New in version 3.3.</span></p>
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</div>
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<div class="versionchanged">
|
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<p><span class="versionmodified changed">Changed in version 3.4: </span>The new file descriptor is now non-inheritable.</p>
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</div>
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</dd></dl>
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<dl class="function">
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<dt id="select.epoll">
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<code class="descclassname">select.</code><code class="descname">epoll</code><span class="sig-paren">(</span><em>sizehint=-1</em>, <em>flags=0</em><span class="sig-paren">)</span><a class="headerlink" href="#select.epoll" title="Permalink to this definition">¶</a></dt>
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<dd><p>(Only supported on Linux 2.5.44 and newer.) Return an edge polling object,
|
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which can be used as Edge or Level Triggered interface for I/O
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events.</p>
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<p><em>sizehint</em> informs epoll about the expected number of events to be
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registered. It must be positive, or <cite>-1</cite> to use the default. It is only
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used on older systems where <code class="xref c c-func docutils literal notranslate"><span class="pre">epoll_create1()</span></code> is not available;
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otherwise it has no effect (though its value is still checked).</p>
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<p><em>flags</em> is deprecated and completely ignored. However, when supplied, its
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value must be <code class="docutils literal notranslate"><span class="pre">0</span></code> or <code class="docutils literal notranslate"><span class="pre">select.EPOLL_CLOEXEC</span></code>, otherwise <code class="docutils literal notranslate"><span class="pre">OSError</span></code> is
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raised.</p>
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<p>See the <a class="reference internal" href="#epoll-objects"><span class="std std-ref">Edge and Level Trigger Polling (epoll) Objects</span></a> section below for the methods supported by
|
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epolling objects.</p>
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<p><code class="docutils literal notranslate"><span class="pre">epoll</span></code> objects support the context management protocol: when used in a
|
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<a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">with</span></code></a> statement, the new file descriptor is automatically closed
|
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at the end of the block.</p>
|
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<p>The new file descriptor is <a class="reference internal" href="os.html#fd-inheritance"><span class="std std-ref">non-inheritable</span></a>.</p>
|
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<div class="versionchanged">
|
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<p><span class="versionmodified changed">Changed in version 3.3: </span>Added the <em>flags</em> parameter.</p>
|
|||
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</div>
|
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<div class="versionchanged">
|
|||
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<p><span class="versionmodified changed">Changed in version 3.4: </span>Support for the <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">with</span></code></a> statement was added.
|
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The new file descriptor is now non-inheritable.</p>
|
|||
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</div>
|
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<div class="deprecated">
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<p><span class="versionmodified deprecated">Deprecated since version 3.4: </span>The <em>flags</em> parameter. <code class="docutils literal notranslate"><span class="pre">select.EPOLL_CLOEXEC</span></code> is used by default now.
|
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Use <a class="reference internal" href="os.html#os.set_inheritable" title="os.set_inheritable"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.set_inheritable()</span></code></a> to make the file descriptor inheritable.</p>
|
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</div>
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</dd></dl>
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<dl class="function">
|
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<dt id="select.poll">
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<code class="descclassname">select.</code><code class="descname">poll</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#select.poll" title="Permalink to this definition">¶</a></dt>
|
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<dd><p>(Not supported by all operating systems.) Returns a polling object, which
|
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supports registering and unregistering file descriptors, and then polling them
|
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for I/O events; see section <a class="reference internal" href="#poll-objects"><span class="std std-ref">Polling Objects</span></a> below for the methods supported
|
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by polling objects.</p>
|
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</dd></dl>
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<dl class="function">
|
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<dt id="select.kqueue">
|
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<code class="descclassname">select.</code><code class="descname">kqueue</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#select.kqueue" title="Permalink to this definition">¶</a></dt>
|
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<dd><p>(Only supported on BSD.) Returns a kernel queue object; see section
|
|||
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<a class="reference internal" href="#kqueue-objects"><span class="std std-ref">Kqueue Objects</span></a> below for the methods supported by kqueue objects.</p>
|
|||
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<p>The new file descriptor is <a class="reference internal" href="os.html#fd-inheritance"><span class="std std-ref">non-inheritable</span></a>.</p>
|
|||
|
|
<div class="versionchanged">
|
|||
|
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<p><span class="versionmodified changed">Changed in version 3.4: </span>The new file descriptor is now non-inheritable.</p>
|
|||
|
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</div>
|
|||
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</dd></dl>
|
|||
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<dl class="function">
|
|||
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<dt id="select.kevent">
|
|||
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<code class="descclassname">select.</code><code class="descname">kevent</code><span class="sig-paren">(</span><em>ident</em>, <em>filter=KQ_FILTER_READ</em>, <em>flags=KQ_EV_ADD</em>, <em>fflags=0</em>, <em>data=0</em>, <em>udata=0</em><span class="sig-paren">)</span><a class="headerlink" href="#select.kevent" title="Permalink to this definition">¶</a></dt>
|
|||
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<dd><p>(Only supported on BSD.) Returns a kernel event object; see section
|
|||
|
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<a class="reference internal" href="#kevent-objects"><span class="std std-ref">Kevent Objects</span></a> below for the methods supported by kevent objects.</p>
|
|||
|
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</dd></dl>
|
|||
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|
|||
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<dl class="function">
|
|||
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<dt id="select.select">
|
|||
|
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<code class="descclassname">select.</code><code class="descname">select</code><span class="sig-paren">(</span><em>rlist</em>, <em>wlist</em>, <em>xlist</em><span class="optional">[</span>, <em>timeout</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#select.select" title="Permalink to this definition">¶</a></dt>
|
|||
|
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<dd><p>This is a straightforward interface to the Unix <code class="xref c c-func docutils literal notranslate"><span class="pre">select()</span></code> system call.
|
|||
|
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The first three arguments are sequences of ‘waitable objects’: either
|
|||
|
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integers representing file descriptors or objects with a parameterless method
|
|||
|
|
named <a class="reference internal" href="io.html#io.IOBase.fileno" title="io.IOBase.fileno"><code class="xref py py-meth docutils literal notranslate"><span class="pre">fileno()</span></code></a> returning such an integer:</p>
|
|||
|
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<ul class="simple">
|
|||
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<li><p><em>rlist</em>: wait until ready for reading</p></li>
|
|||
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<li><p><em>wlist</em>: wait until ready for writing</p></li>
|
|||
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<li><p><em>xlist</em>: wait for an “exceptional condition” (see the manual page for what
|
|||
|
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your system considers such a condition)</p></li>
|
|||
|
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</ul>
|
|||
|
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<p>Empty sequences are allowed, but acceptance of three empty sequences is
|
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platform-dependent. (It is known to work on Unix but not on Windows.) The
|
|||
|
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optional <em>timeout</em> argument specifies a time-out as a floating point number
|
|||
|
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in seconds. When the <em>timeout</em> argument is omitted the function blocks until
|
|||
|
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at least one file descriptor is ready. A time-out value of zero specifies a
|
|||
|
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poll and never blocks.</p>
|
|||
|
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<p>The return value is a triple of lists of objects that are ready: subsets of the
|
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first three arguments. When the time-out is reached without a file descriptor
|
|||
|
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becoming ready, three empty lists are returned.</p>
|
|||
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<p id="index-1">Among the acceptable object types in the sequences are Python <a class="reference internal" href="../glossary.html#term-file-object"><span class="xref std std-term">file
|
|||
|
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objects</span></a> (e.g. <code class="docutils literal notranslate"><span class="pre">sys.stdin</span></code>, or objects returned by
|
|||
|
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<a class="reference internal" href="functions.html#open" title="open"><code class="xref py py-func docutils literal notranslate"><span class="pre">open()</span></code></a> or <a class="reference internal" href="os.html#os.popen" title="os.popen"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.popen()</span></code></a>), socket objects returned by
|
|||
|
|
<a class="reference internal" href="socket.html#socket.socket" title="socket.socket"><code class="xref py py-func docutils literal notranslate"><span class="pre">socket.socket()</span></code></a>. You may also define a <em class="dfn">wrapper</em> class yourself,
|
|||
|
|
as long as it has an appropriate <a class="reference internal" href="io.html#io.IOBase.fileno" title="io.IOBase.fileno"><code class="xref py py-meth docutils literal notranslate"><span class="pre">fileno()</span></code></a> method (that
|
|||
|
|
really returns a file descriptor, not just a random integer).</p>
|
|||
|
|
<div class="admonition note">
|
|||
|
|
<p class="admonition-title">Note</p>
|
|||
|
|
<p id="index-2">File objects on Windows are not acceptable, but sockets are. On Windows,
|
|||
|
|
the underlying <code class="xref c c-func docutils literal notranslate"><span class="pre">select()</span></code> function is provided by the WinSock
|
|||
|
|
library, and does not handle file descriptors that don’t originate from
|
|||
|
|
WinSock.</p>
|
|||
|
|
</div>
|
|||
|
|
<div class="versionchanged">
|
|||
|
|
<p><span class="versionmodified changed">Changed in version 3.5: </span>The function is now retried with a recomputed timeout when interrupted by
|
|||
|
|
a signal, except if the signal handler raises an exception (see
|
|||
|
|
<span class="target" id="index-3"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0475"><strong>PEP 475</strong></a> for the rationale), instead of raising
|
|||
|
|
<a class="reference internal" href="exceptions.html#InterruptedError" title="InterruptedError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">InterruptedError</span></code></a>.</p>
|
|||
|
|
</div>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
<dl class="attribute">
|
|||
|
|
<dt id="select.PIPE_BUF">
|
|||
|
|
<code class="descclassname">select.</code><code class="descname">PIPE_BUF</code><a class="headerlink" href="#select.PIPE_BUF" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>The minimum number of bytes which can be written without blocking to a pipe
|
|||
|
|
when the pipe has been reported as ready for writing by <a class="reference internal" href="#select.select" title="select.select"><code class="xref py py-func docutils literal notranslate"><span class="pre">select()</span></code></a>,
|
|||
|
|
<a class="reference internal" href="#select.poll" title="select.poll"><code class="xref py py-func docutils literal notranslate"><span class="pre">poll()</span></code></a> or another interface in this module. This doesn’t apply
|
|||
|
|
to other kind of file-like objects such as sockets.</p>
|
|||
|
|
<p>This value is guaranteed by POSIX to be at least 512.</p>
|
|||
|
|
<p class="availability"><a class="reference internal" href="intro.html#availability"><span class="std std-ref">Availability</span></a>: Unix</p>
|
|||
|
|
<div class="versionadded">
|
|||
|
|
<p><span class="versionmodified added">New in version 3.2.</span></p>
|
|||
|
|
</div>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
<div class="section" id="dev-poll-polling-objects">
|
|||
|
|
<span id="devpoll-objects"></span><h2><code class="docutils literal notranslate"><span class="pre">/dev/poll</span></code> Polling Objects<a class="headerlink" href="#dev-poll-polling-objects" title="Permalink to this headline">¶</a></h2>
|
|||
|
|
<p>Solaris and derivatives have <code class="docutils literal notranslate"><span class="pre">/dev/poll</span></code>. While <code class="xref c c-func docutils literal notranslate"><span class="pre">select()</span></code> is
|
|||
|
|
O(highest file descriptor) and <code class="xref c c-func docutils literal notranslate"><span class="pre">poll()</span></code> is O(number of file
|
|||
|
|
descriptors), <code class="docutils literal notranslate"><span class="pre">/dev/poll</span></code> is O(active file descriptors).</p>
|
|||
|
|
<p><code class="docutils literal notranslate"><span class="pre">/dev/poll</span></code> behaviour is very close to the standard <code class="xref c c-func docutils literal notranslate"><span class="pre">poll()</span></code>
|
|||
|
|
object.</p>
|
|||
|
|
<dl class="method">
|
|||
|
|
<dt id="select.devpoll.close">
|
|||
|
|
<code class="descclassname">devpoll.</code><code class="descname">close</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#select.devpoll.close" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>Close the file descriptor of the polling object.</p>
|
|||
|
|
<div class="versionadded">
|
|||
|
|
<p><span class="versionmodified added">New in version 3.4.</span></p>
|
|||
|
|
</div>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
<dl class="attribute">
|
|||
|
|
<dt id="select.devpoll.closed">
|
|||
|
|
<code class="descclassname">devpoll.</code><code class="descname">closed</code><a class="headerlink" href="#select.devpoll.closed" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p><code class="docutils literal notranslate"><span class="pre">True</span></code> if the polling object is closed.</p>
|
|||
|
|
<div class="versionadded">
|
|||
|
|
<p><span class="versionmodified added">New in version 3.4.</span></p>
|
|||
|
|
</div>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
<dl class="method">
|
|||
|
|
<dt id="select.devpoll.fileno">
|
|||
|
|
<code class="descclassname">devpoll.</code><code class="descname">fileno</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#select.devpoll.fileno" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>Return the file descriptor number of the polling object.</p>
|
|||
|
|
<div class="versionadded">
|
|||
|
|
<p><span class="versionmodified added">New in version 3.4.</span></p>
|
|||
|
|
</div>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
<dl class="method">
|
|||
|
|
<dt id="select.devpoll.register">
|
|||
|
|
<code class="descclassname">devpoll.</code><code class="descname">register</code><span class="sig-paren">(</span><em>fd</em><span class="optional">[</span>, <em>eventmask</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#select.devpoll.register" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>Register a file descriptor with the polling object. Future calls to the
|
|||
|
|
<a class="reference internal" href="#select.poll" title="select.poll"><code class="xref py py-meth docutils literal notranslate"><span class="pre">poll()</span></code></a> method will then check whether the file descriptor has any
|
|||
|
|
pending I/O events. <em>fd</em> can be either an integer, or an object with a
|
|||
|
|
<a class="reference internal" href="io.html#io.IOBase.fileno" title="io.IOBase.fileno"><code class="xref py py-meth docutils literal notranslate"><span class="pre">fileno()</span></code></a> method that returns an integer. File objects
|
|||
|
|
implement <code class="xref py py-meth docutils literal notranslate"><span class="pre">fileno()</span></code>, so they can also be used as the argument.</p>
|
|||
|
|
<p><em>eventmask</em> is an optional bitmask describing the type of events you want to
|
|||
|
|
check for. The constants are the same that with <code class="xref c c-func docutils literal notranslate"><span class="pre">poll()</span></code>
|
|||
|
|
object. The default value is a combination of the constants <code class="xref py py-const docutils literal notranslate"><span class="pre">POLLIN</span></code>,
|
|||
|
|
<code class="xref py py-const docutils literal notranslate"><span class="pre">POLLPRI</span></code>, and <code class="xref py py-const docutils literal notranslate"><span class="pre">POLLOUT</span></code>.</p>
|
|||
|
|
<div class="admonition warning">
|
|||
|
|
<p class="admonition-title">Warning</p>
|
|||
|
|
<p>Registering a file descriptor that’s already registered is not an
|
|||
|
|
error, but the result is undefined. The appropriate action is to
|
|||
|
|
unregister or modify it first. This is an important difference
|
|||
|
|
compared with <code class="xref c c-func docutils literal notranslate"><span class="pre">poll()</span></code>.</p>
|
|||
|
|
</div>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
<dl class="method">
|
|||
|
|
<dt id="select.devpoll.modify">
|
|||
|
|
<code class="descclassname">devpoll.</code><code class="descname">modify</code><span class="sig-paren">(</span><em>fd</em><span class="optional">[</span>, <em>eventmask</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#select.devpoll.modify" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>This method does an <a class="reference internal" href="#select.devpoll.unregister" title="select.devpoll.unregister"><code class="xref py py-meth docutils literal notranslate"><span class="pre">unregister()</span></code></a> followed by a
|
|||
|
|
<a class="reference internal" href="#select.devpoll.register" title="select.devpoll.register"><code class="xref py py-meth docutils literal notranslate"><span class="pre">register()</span></code></a>. It is (a bit) more efficient that doing the same
|
|||
|
|
explicitly.</p>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
<dl class="method">
|
|||
|
|
<dt id="select.devpoll.unregister">
|
|||
|
|
<code class="descclassname">devpoll.</code><code class="descname">unregister</code><span class="sig-paren">(</span><em>fd</em><span class="sig-paren">)</span><a class="headerlink" href="#select.devpoll.unregister" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>Remove a file descriptor being tracked by a polling object. Just like the
|
|||
|
|
<a class="reference internal" href="#select.devpoll.register" title="select.devpoll.register"><code class="xref py py-meth docutils literal notranslate"><span class="pre">register()</span></code></a> method, <em>fd</em> can be an integer or an object with a
|
|||
|
|
<a class="reference internal" href="io.html#io.IOBase.fileno" title="io.IOBase.fileno"><code class="xref py py-meth docutils literal notranslate"><span class="pre">fileno()</span></code></a> method that returns an integer.</p>
|
|||
|
|
<p>Attempting to remove a file descriptor that was never registered is
|
|||
|
|
safely ignored.</p>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
<dl class="method">
|
|||
|
|
<dt id="select.devpoll.poll">
|
|||
|
|
<code class="descclassname">devpoll.</code><code class="descname">poll</code><span class="sig-paren">(</span><span class="optional">[</span><em>timeout</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#select.devpoll.poll" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>Polls the set of registered file descriptors, and returns a possibly-empty list
|
|||
|
|
containing <code class="docutils literal notranslate"><span class="pre">(fd,</span> <span class="pre">event)</span></code> 2-tuples for the descriptors that have events or
|
|||
|
|
errors to report. <em>fd</em> is the file descriptor, and <em>event</em> is a bitmask with
|
|||
|
|
bits set for the reported events for that descriptor — <code class="xref py py-const docutils literal notranslate"><span class="pre">POLLIN</span></code> for
|
|||
|
|
waiting input, <code class="xref py py-const docutils literal notranslate"><span class="pre">POLLOUT</span></code> to indicate that the descriptor can be written
|
|||
|
|
to, and so forth. An empty list indicates that the call timed out and no file
|
|||
|
|
descriptors had any events to report. If <em>timeout</em> is given, it specifies the
|
|||
|
|
length of time in milliseconds which the system will wait for events before
|
|||
|
|
returning. If <em>timeout</em> is omitted, -1, or <a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal notranslate"><span class="pre">None</span></code></a>, the call will
|
|||
|
|
block until there is an event for this poll object.</p>
|
|||
|
|
<div class="versionchanged">
|
|||
|
|
<p><span class="versionmodified changed">Changed in version 3.5: </span>The function is now retried with a recomputed timeout when interrupted by
|
|||
|
|
a signal, except if the signal handler raises an exception (see
|
|||
|
|
<span class="target" id="index-4"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0475"><strong>PEP 475</strong></a> for the rationale), instead of raising
|
|||
|
|
<a class="reference internal" href="exceptions.html#InterruptedError" title="InterruptedError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">InterruptedError</span></code></a>.</p>
|
|||
|
|
</div>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
</div>
|
|||
|
|
<div class="section" id="edge-and-level-trigger-polling-epoll-objects">
|
|||
|
|
<span id="epoll-objects"></span><h2>Edge and Level Trigger Polling (epoll) Objects<a class="headerlink" href="#edge-and-level-trigger-polling-epoll-objects" title="Permalink to this headline">¶</a></h2>
|
|||
|
|
<blockquote>
|
|||
|
|
<div><p><a class="reference external" href="https://linux.die.net/man/4/epoll">https://linux.die.net/man/4/epoll</a></p>
|
|||
|
|
<p><em>eventmask</em></p>
|
|||
|
|
<table class="docutils align-center">
|
|||
|
|
<colgroup>
|
|||
|
|
<col style="width: 35%" />
|
|||
|
|
<col style="width: 65%" />
|
|||
|
|
</colgroup>
|
|||
|
|
<thead>
|
|||
|
|
<tr class="row-odd"><th class="head"><p>Constant</p></th>
|
|||
|
|
<th class="head"><p>Meaning</p></th>
|
|||
|
|
</tr>
|
|||
|
|
</thead>
|
|||
|
|
<tbody>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">EPOLLIN</span></code></p></td>
|
|||
|
|
<td><p>Available for read</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">EPOLLOUT</span></code></p></td>
|
|||
|
|
<td><p>Available for write</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">EPOLLPRI</span></code></p></td>
|
|||
|
|
<td><p>Urgent data for read</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">EPOLLERR</span></code></p></td>
|
|||
|
|
<td><p>Error condition happened on the assoc. fd</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">EPOLLHUP</span></code></p></td>
|
|||
|
|
<td><p>Hang up happened on the assoc. fd</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">EPOLLET</span></code></p></td>
|
|||
|
|
<td><p>Set Edge Trigger behavior, the default is
|
|||
|
|
Level Trigger behavior</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">EPOLLONESHOT</span></code></p></td>
|
|||
|
|
<td><p>Set one-shot behavior. After one event is
|
|||
|
|
pulled out, the fd is internally disabled</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">EPOLLEXCLUSIVE</span></code></p></td>
|
|||
|
|
<td><p>Wake only one epoll object when the
|
|||
|
|
associated fd has an event. The default (if
|
|||
|
|
this flag is not set) is to wake all epoll
|
|||
|
|
objects polling on a fd.</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">EPOLLRDHUP</span></code></p></td>
|
|||
|
|
<td><p>Stream socket peer closed connection or shut
|
|||
|
|
down writing half of connection.</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">EPOLLRDNORM</span></code></p></td>
|
|||
|
|
<td><p>Equivalent to <code class="xref py py-const docutils literal notranslate"><span class="pre">EPOLLIN</span></code></p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">EPOLLRDBAND</span></code></p></td>
|
|||
|
|
<td><p>Priority data band can be read.</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">EPOLLWRNORM</span></code></p></td>
|
|||
|
|
<td><p>Equivalent to <code class="xref py py-const docutils literal notranslate"><span class="pre">EPOLLOUT</span></code></p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">EPOLLWRBAND</span></code></p></td>
|
|||
|
|
<td><p>Priority data may be written.</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">EPOLLMSG</span></code></p></td>
|
|||
|
|
<td><p>Ignored.</p></td>
|
|||
|
|
</tr>
|
|||
|
|
</tbody>
|
|||
|
|
</table>
|
|||
|
|
<div class="versionadded">
|
|||
|
|
<p><span class="versionmodified added">New in version 3.6: </span><code class="xref py py-const docutils literal notranslate"><span class="pre">EPOLLEXCLUSIVE</span></code> was added. It’s only supported by Linux Kernel 4.5
|
|||
|
|
or later.</p>
|
|||
|
|
</div>
|
|||
|
|
</div></blockquote>
|
|||
|
|
<dl class="method">
|
|||
|
|
<dt id="select.epoll.close">
|
|||
|
|
<code class="descclassname">epoll.</code><code class="descname">close</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#select.epoll.close" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>Close the control file descriptor of the epoll object.</p>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
<dl class="attribute">
|
|||
|
|
<dt id="select.epoll.closed">
|
|||
|
|
<code class="descclassname">epoll.</code><code class="descname">closed</code><a class="headerlink" href="#select.epoll.closed" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p><code class="docutils literal notranslate"><span class="pre">True</span></code> if the epoll object is closed.</p>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
<dl class="method">
|
|||
|
|
<dt id="select.epoll.fileno">
|
|||
|
|
<code class="descclassname">epoll.</code><code class="descname">fileno</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#select.epoll.fileno" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>Return the file descriptor number of the control fd.</p>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
<dl class="method">
|
|||
|
|
<dt id="select.epoll.fromfd">
|
|||
|
|
<code class="descclassname">epoll.</code><code class="descname">fromfd</code><span class="sig-paren">(</span><em>fd</em><span class="sig-paren">)</span><a class="headerlink" href="#select.epoll.fromfd" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>Create an epoll object from a given file descriptor.</p>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
<dl class="method">
|
|||
|
|
<dt id="select.epoll.register">
|
|||
|
|
<code class="descclassname">epoll.</code><code class="descname">register</code><span class="sig-paren">(</span><em>fd</em><span class="optional">[</span>, <em>eventmask</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#select.epoll.register" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>Register a fd descriptor with the epoll object.</p>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
<dl class="method">
|
|||
|
|
<dt id="select.epoll.modify">
|
|||
|
|
<code class="descclassname">epoll.</code><code class="descname">modify</code><span class="sig-paren">(</span><em>fd</em>, <em>eventmask</em><span class="sig-paren">)</span><a class="headerlink" href="#select.epoll.modify" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>Modify a registered file descriptor.</p>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
<dl class="method">
|
|||
|
|
<dt id="select.epoll.unregister">
|
|||
|
|
<code class="descclassname">epoll.</code><code class="descname">unregister</code><span class="sig-paren">(</span><em>fd</em><span class="sig-paren">)</span><a class="headerlink" href="#select.epoll.unregister" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>Remove a registered file descriptor from the epoll object.</p>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
<dl class="method">
|
|||
|
|
<dt id="select.epoll.poll">
|
|||
|
|
<code class="descclassname">epoll.</code><code class="descname">poll</code><span class="sig-paren">(</span><em>timeout=-1</em>, <em>maxevents=-1</em><span class="sig-paren">)</span><a class="headerlink" href="#select.epoll.poll" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>Wait for events. timeout in seconds (float)</p>
|
|||
|
|
<div class="versionchanged">
|
|||
|
|
<p><span class="versionmodified changed">Changed in version 3.5: </span>The function is now retried with a recomputed timeout when interrupted by
|
|||
|
|
a signal, except if the signal handler raises an exception (see
|
|||
|
|
<span class="target" id="index-5"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0475"><strong>PEP 475</strong></a> for the rationale), instead of raising
|
|||
|
|
<a class="reference internal" href="exceptions.html#InterruptedError" title="InterruptedError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">InterruptedError</span></code></a>.</p>
|
|||
|
|
</div>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
</div>
|
|||
|
|
<div class="section" id="polling-objects">
|
|||
|
|
<span id="poll-objects"></span><h2>Polling Objects<a class="headerlink" href="#polling-objects" title="Permalink to this headline">¶</a></h2>
|
|||
|
|
<p>The <code class="xref c c-func docutils literal notranslate"><span class="pre">poll()</span></code> system call, supported on most Unix systems, provides better
|
|||
|
|
scalability for network servers that service many, many clients at the same
|
|||
|
|
time. <code class="xref c c-func docutils literal notranslate"><span class="pre">poll()</span></code> scales better because the system call only requires listing
|
|||
|
|
the file descriptors of interest, while <code class="xref c c-func docutils literal notranslate"><span class="pre">select()</span></code> builds a bitmap, turns
|
|||
|
|
on bits for the fds of interest, and then afterward the whole bitmap has to be
|
|||
|
|
linearly scanned again. <code class="xref c c-func docutils literal notranslate"><span class="pre">select()</span></code> is O(highest file descriptor), while
|
|||
|
|
<code class="xref c c-func docutils literal notranslate"><span class="pre">poll()</span></code> is O(number of file descriptors).</p>
|
|||
|
|
<dl class="method">
|
|||
|
|
<dt id="select.poll.register">
|
|||
|
|
<code class="descclassname">poll.</code><code class="descname">register</code><span class="sig-paren">(</span><em>fd</em><span class="optional">[</span>, <em>eventmask</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#select.poll.register" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>Register a file descriptor with the polling object. Future calls to the
|
|||
|
|
<a class="reference internal" href="#select.poll" title="select.poll"><code class="xref py py-meth docutils literal notranslate"><span class="pre">poll()</span></code></a> method will then check whether the file descriptor has any
|
|||
|
|
pending I/O events. <em>fd</em> can be either an integer, or an object with a
|
|||
|
|
<a class="reference internal" href="io.html#io.IOBase.fileno" title="io.IOBase.fileno"><code class="xref py py-meth docutils literal notranslate"><span class="pre">fileno()</span></code></a> method that returns an integer. File objects
|
|||
|
|
implement <code class="xref py py-meth docutils literal notranslate"><span class="pre">fileno()</span></code>, so they can also be used as the argument.</p>
|
|||
|
|
<p><em>eventmask</em> is an optional bitmask describing the type of events you want to
|
|||
|
|
check for, and can be a combination of the constants <code class="xref py py-const docutils literal notranslate"><span class="pre">POLLIN</span></code>,
|
|||
|
|
<code class="xref py py-const docutils literal notranslate"><span class="pre">POLLPRI</span></code>, and <code class="xref py py-const docutils literal notranslate"><span class="pre">POLLOUT</span></code>, described in the table below. If not
|
|||
|
|
specified, the default value used will check for all 3 types of events.</p>
|
|||
|
|
<table class="docutils align-center">
|
|||
|
|
<colgroup>
|
|||
|
|
<col style="width: 31%" />
|
|||
|
|
<col style="width: 69%" />
|
|||
|
|
</colgroup>
|
|||
|
|
<thead>
|
|||
|
|
<tr class="row-odd"><th class="head"><p>Constant</p></th>
|
|||
|
|
<th class="head"><p>Meaning</p></th>
|
|||
|
|
</tr>
|
|||
|
|
</thead>
|
|||
|
|
<tbody>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">POLLIN</span></code></p></td>
|
|||
|
|
<td><p>There is data to read</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">POLLPRI</span></code></p></td>
|
|||
|
|
<td><p>There is urgent data to read</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">POLLOUT</span></code></p></td>
|
|||
|
|
<td><p>Ready for output: writing will not block</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">POLLERR</span></code></p></td>
|
|||
|
|
<td><p>Error condition of some sort</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">POLLHUP</span></code></p></td>
|
|||
|
|
<td><p>Hung up</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">POLLRDHUP</span></code></p></td>
|
|||
|
|
<td><p>Stream socket peer closed connection, or
|
|||
|
|
shut down writing half of connection</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">POLLNVAL</span></code></p></td>
|
|||
|
|
<td><p>Invalid request: descriptor not open</p></td>
|
|||
|
|
</tr>
|
|||
|
|
</tbody>
|
|||
|
|
</table>
|
|||
|
|
<p>Registering a file descriptor that’s already registered is not an error, and has
|
|||
|
|
the same effect as registering the descriptor exactly once.</p>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
<dl class="method">
|
|||
|
|
<dt id="select.poll.modify">
|
|||
|
|
<code class="descclassname">poll.</code><code class="descname">modify</code><span class="sig-paren">(</span><em>fd</em>, <em>eventmask</em><span class="sig-paren">)</span><a class="headerlink" href="#select.poll.modify" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>Modifies an already registered fd. This has the same effect as
|
|||
|
|
<code class="docutils literal notranslate"><span class="pre">register(fd,</span> <span class="pre">eventmask)</span></code>. Attempting to modify a file descriptor
|
|||
|
|
that was never registered causes an <a class="reference internal" href="exceptions.html#OSError" title="OSError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">OSError</span></code></a> exception with errno
|
|||
|
|
<code class="xref py py-const docutils literal notranslate"><span class="pre">ENOENT</span></code> to be raised.</p>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
<dl class="method">
|
|||
|
|
<dt id="select.poll.unregister">
|
|||
|
|
<code class="descclassname">poll.</code><code class="descname">unregister</code><span class="sig-paren">(</span><em>fd</em><span class="sig-paren">)</span><a class="headerlink" href="#select.poll.unregister" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>Remove a file descriptor being tracked by a polling object. Just like the
|
|||
|
|
<a class="reference internal" href="#select.poll.register" title="select.poll.register"><code class="xref py py-meth docutils literal notranslate"><span class="pre">register()</span></code></a> method, <em>fd</em> can be an integer or an object with a
|
|||
|
|
<a class="reference internal" href="io.html#io.IOBase.fileno" title="io.IOBase.fileno"><code class="xref py py-meth docutils literal notranslate"><span class="pre">fileno()</span></code></a> method that returns an integer.</p>
|
|||
|
|
<p>Attempting to remove a file descriptor that was never registered causes a
|
|||
|
|
<a class="reference internal" href="exceptions.html#KeyError" title="KeyError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">KeyError</span></code></a> exception to be raised.</p>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
<dl class="method">
|
|||
|
|
<dt id="select.poll.poll">
|
|||
|
|
<code class="descclassname">poll.</code><code class="descname">poll</code><span class="sig-paren">(</span><span class="optional">[</span><em>timeout</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#select.poll.poll" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>Polls the set of registered file descriptors, and returns a possibly-empty list
|
|||
|
|
containing <code class="docutils literal notranslate"><span class="pre">(fd,</span> <span class="pre">event)</span></code> 2-tuples for the descriptors that have events or
|
|||
|
|
errors to report. <em>fd</em> is the file descriptor, and <em>event</em> is a bitmask with
|
|||
|
|
bits set for the reported events for that descriptor — <code class="xref py py-const docutils literal notranslate"><span class="pre">POLLIN</span></code> for
|
|||
|
|
waiting input, <code class="xref py py-const docutils literal notranslate"><span class="pre">POLLOUT</span></code> to indicate that the descriptor can be written
|
|||
|
|
to, and so forth. An empty list indicates that the call timed out and no file
|
|||
|
|
descriptors had any events to report. If <em>timeout</em> is given, it specifies the
|
|||
|
|
length of time in milliseconds which the system will wait for events before
|
|||
|
|
returning. If <em>timeout</em> is omitted, negative, or <a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal notranslate"><span class="pre">None</span></code></a>, the call will
|
|||
|
|
block until there is an event for this poll object.</p>
|
|||
|
|
<div class="versionchanged">
|
|||
|
|
<p><span class="versionmodified changed">Changed in version 3.5: </span>The function is now retried with a recomputed timeout when interrupted by
|
|||
|
|
a signal, except if the signal handler raises an exception (see
|
|||
|
|
<span class="target" id="index-6"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0475"><strong>PEP 475</strong></a> for the rationale), instead of raising
|
|||
|
|
<a class="reference internal" href="exceptions.html#InterruptedError" title="InterruptedError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">InterruptedError</span></code></a>.</p>
|
|||
|
|
</div>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
</div>
|
|||
|
|
<div class="section" id="kqueue-objects">
|
|||
|
|
<span id="id1"></span><h2>Kqueue Objects<a class="headerlink" href="#kqueue-objects" title="Permalink to this headline">¶</a></h2>
|
|||
|
|
<dl class="method">
|
|||
|
|
<dt id="select.kqueue.close">
|
|||
|
|
<code class="descclassname">kqueue.</code><code class="descname">close</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#select.kqueue.close" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>Close the control file descriptor of the kqueue object.</p>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
<dl class="attribute">
|
|||
|
|
<dt id="select.kqueue.closed">
|
|||
|
|
<code class="descclassname">kqueue.</code><code class="descname">closed</code><a class="headerlink" href="#select.kqueue.closed" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p><code class="docutils literal notranslate"><span class="pre">True</span></code> if the kqueue object is closed.</p>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
<dl class="method">
|
|||
|
|
<dt id="select.kqueue.fileno">
|
|||
|
|
<code class="descclassname">kqueue.</code><code class="descname">fileno</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#select.kqueue.fileno" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>Return the file descriptor number of the control fd.</p>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
<dl class="method">
|
|||
|
|
<dt id="select.kqueue.fromfd">
|
|||
|
|
<code class="descclassname">kqueue.</code><code class="descname">fromfd</code><span class="sig-paren">(</span><em>fd</em><span class="sig-paren">)</span><a class="headerlink" href="#select.kqueue.fromfd" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>Create a kqueue object from a given file descriptor.</p>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
<dl class="method">
|
|||
|
|
<dt id="select.kqueue.control">
|
|||
|
|
<code class="descclassname">kqueue.</code><code class="descname">control</code><span class="sig-paren">(</span><em>changelist</em>, <em>max_events</em><span class="optional">[</span>, <em>timeout</em><span class="optional">]</span><span class="sig-paren">)</span> → eventlist<a class="headerlink" href="#select.kqueue.control" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>Low level interface to kevent</p>
|
|||
|
|
<ul class="simple">
|
|||
|
|
<li><p>changelist must be an iterable of kevent objects or <code class="docutils literal notranslate"><span class="pre">None</span></code></p></li>
|
|||
|
|
<li><p>max_events must be 0 or a positive integer</p></li>
|
|||
|
|
<li><p>timeout in seconds (floats possible); the default is <code class="docutils literal notranslate"><span class="pre">None</span></code>,
|
|||
|
|
to wait forever</p></li>
|
|||
|
|
</ul>
|
|||
|
|
<div class="versionchanged">
|
|||
|
|
<p><span class="versionmodified changed">Changed in version 3.5: </span>The function is now retried with a recomputed timeout when interrupted by
|
|||
|
|
a signal, except if the signal handler raises an exception (see
|
|||
|
|
<span class="target" id="index-7"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0475"><strong>PEP 475</strong></a> for the rationale), instead of raising
|
|||
|
|
<a class="reference internal" href="exceptions.html#InterruptedError" title="InterruptedError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">InterruptedError</span></code></a>.</p>
|
|||
|
|
</div>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
</div>
|
|||
|
|
<div class="section" id="kevent-objects">
|
|||
|
|
<span id="id2"></span><h2>Kevent Objects<a class="headerlink" href="#kevent-objects" title="Permalink to this headline">¶</a></h2>
|
|||
|
|
<p><a class="reference external" href="https://www.freebsd.org/cgi/man.cgi?query=kqueue&sektion=2">https://www.freebsd.org/cgi/man.cgi?query=kqueue&sektion=2</a></p>
|
|||
|
|
<dl class="attribute">
|
|||
|
|
<dt id="select.kevent.ident">
|
|||
|
|
<code class="descclassname">kevent.</code><code class="descname">ident</code><a class="headerlink" href="#select.kevent.ident" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>Value used to identify the event. The interpretation depends on the filter
|
|||
|
|
but it’s usually the file descriptor. In the constructor ident can either
|
|||
|
|
be an int or an object with a <a class="reference internal" href="io.html#io.IOBase.fileno" title="io.IOBase.fileno"><code class="xref py py-meth docutils literal notranslate"><span class="pre">fileno()</span></code></a> method. kevent
|
|||
|
|
stores the integer internally.</p>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
<dl class="attribute">
|
|||
|
|
<dt id="select.kevent.filter">
|
|||
|
|
<code class="descclassname">kevent.</code><code class="descname">filter</code><a class="headerlink" href="#select.kevent.filter" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>Name of the kernel filter.</p>
|
|||
|
|
<table class="docutils align-center">
|
|||
|
|
<colgroup>
|
|||
|
|
<col style="width: 38%" />
|
|||
|
|
<col style="width: 63%" />
|
|||
|
|
</colgroup>
|
|||
|
|
<thead>
|
|||
|
|
<tr class="row-odd"><th class="head"><p>Constant</p></th>
|
|||
|
|
<th class="head"><p>Meaning</p></th>
|
|||
|
|
</tr>
|
|||
|
|
</thead>
|
|||
|
|
<tbody>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_FILTER_READ</span></code></p></td>
|
|||
|
|
<td><p>Takes a descriptor and returns whenever
|
|||
|
|
there is data available to read</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_FILTER_WRITE</span></code></p></td>
|
|||
|
|
<td><p>Takes a descriptor and returns whenever
|
|||
|
|
there is data available to write</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_FILTER_AIO</span></code></p></td>
|
|||
|
|
<td><p>AIO requests</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_FILTER_VNODE</span></code></p></td>
|
|||
|
|
<td><p>Returns when one or more of the requested
|
|||
|
|
events watched in <em>fflag</em> occurs</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_FILTER_PROC</span></code></p></td>
|
|||
|
|
<td><p>Watch for events on a process id</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_FILTER_NETDEV</span></code></p></td>
|
|||
|
|
<td><p>Watch for events on a network device
|
|||
|
|
[not available on Mac OS X]</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_FILTER_SIGNAL</span></code></p></td>
|
|||
|
|
<td><p>Returns whenever the watched signal is
|
|||
|
|
delivered to the process</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_FILTER_TIMER</span></code></p></td>
|
|||
|
|
<td><p>Establishes an arbitrary timer</p></td>
|
|||
|
|
</tr>
|
|||
|
|
</tbody>
|
|||
|
|
</table>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
<dl class="attribute">
|
|||
|
|
<dt id="select.kevent.flags">
|
|||
|
|
<code class="descclassname">kevent.</code><code class="descname">flags</code><a class="headerlink" href="#select.kevent.flags" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>Filter action.</p>
|
|||
|
|
<table class="docutils align-center">
|
|||
|
|
<colgroup>
|
|||
|
|
<col style="width: 38%" />
|
|||
|
|
<col style="width: 63%" />
|
|||
|
|
</colgroup>
|
|||
|
|
<thead>
|
|||
|
|
<tr class="row-odd"><th class="head"><p>Constant</p></th>
|
|||
|
|
<th class="head"><p>Meaning</p></th>
|
|||
|
|
</tr>
|
|||
|
|
</thead>
|
|||
|
|
<tbody>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_EV_ADD</span></code></p></td>
|
|||
|
|
<td><p>Adds or modifies an event</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_EV_DELETE</span></code></p></td>
|
|||
|
|
<td><p>Removes an event from the queue</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_EV_ENABLE</span></code></p></td>
|
|||
|
|
<td><p>Permitscontrol() to returns the event</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_EV_DISABLE</span></code></p></td>
|
|||
|
|
<td><p>Disablesevent</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_EV_ONESHOT</span></code></p></td>
|
|||
|
|
<td><p>Removes event after first occurrence</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_EV_CLEAR</span></code></p></td>
|
|||
|
|
<td><p>Reset the state after an event is retrieved</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_EV_SYSFLAGS</span></code></p></td>
|
|||
|
|
<td><p>internal event</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_EV_FLAG1</span></code></p></td>
|
|||
|
|
<td><p>internal event</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_EV_EOF</span></code></p></td>
|
|||
|
|
<td><p>Filter specific EOF condition</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_EV_ERROR</span></code></p></td>
|
|||
|
|
<td><p>See return values</p></td>
|
|||
|
|
</tr>
|
|||
|
|
</tbody>
|
|||
|
|
</table>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
<dl class="attribute">
|
|||
|
|
<dt id="select.kevent.fflags">
|
|||
|
|
<code class="descclassname">kevent.</code><code class="descname">fflags</code><a class="headerlink" href="#select.kevent.fflags" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>Filter specific flags.</p>
|
|||
|
|
<p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_FILTER_READ</span></code> and <code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_FILTER_WRITE</span></code> filter flags:</p>
|
|||
|
|
<table class="docutils align-center">
|
|||
|
|
<colgroup>
|
|||
|
|
<col style="width: 39%" />
|
|||
|
|
<col style="width: 61%" />
|
|||
|
|
</colgroup>
|
|||
|
|
<thead>
|
|||
|
|
<tr class="row-odd"><th class="head"><p>Constant</p></th>
|
|||
|
|
<th class="head"><p>Meaning</p></th>
|
|||
|
|
</tr>
|
|||
|
|
</thead>
|
|||
|
|
<tbody>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_NOTE_LOWAT</span></code></p></td>
|
|||
|
|
<td><p>low water mark of a socket buffer</p></td>
|
|||
|
|
</tr>
|
|||
|
|
</tbody>
|
|||
|
|
</table>
|
|||
|
|
<p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_FILTER_VNODE</span></code> filter flags:</p>
|
|||
|
|
<table class="docutils align-center">
|
|||
|
|
<colgroup>
|
|||
|
|
<col style="width: 39%" />
|
|||
|
|
<col style="width: 61%" />
|
|||
|
|
</colgroup>
|
|||
|
|
<thead>
|
|||
|
|
<tr class="row-odd"><th class="head"><p>Constant</p></th>
|
|||
|
|
<th class="head"><p>Meaning</p></th>
|
|||
|
|
</tr>
|
|||
|
|
</thead>
|
|||
|
|
<tbody>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_NOTE_DELETE</span></code></p></td>
|
|||
|
|
<td><p><em>unlink()</em> was called</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_NOTE_WRITE</span></code></p></td>
|
|||
|
|
<td><p>a write occurred</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_NOTE_EXTEND</span></code></p></td>
|
|||
|
|
<td><p>the file was extended</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_NOTE_ATTRIB</span></code></p></td>
|
|||
|
|
<td><p>an attribute was changed</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_NOTE_LINK</span></code></p></td>
|
|||
|
|
<td><p>the link count has changed</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_NOTE_RENAME</span></code></p></td>
|
|||
|
|
<td><p>the file was renamed</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_NOTE_REVOKE</span></code></p></td>
|
|||
|
|
<td><p>access to the file was revoked</p></td>
|
|||
|
|
</tr>
|
|||
|
|
</tbody>
|
|||
|
|
</table>
|
|||
|
|
<p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_FILTER_PROC</span></code> filter flags:</p>
|
|||
|
|
<table class="docutils align-center">
|
|||
|
|
<colgroup>
|
|||
|
|
<col style="width: 39%" />
|
|||
|
|
<col style="width: 61%" />
|
|||
|
|
</colgroup>
|
|||
|
|
<thead>
|
|||
|
|
<tr class="row-odd"><th class="head"><p>Constant</p></th>
|
|||
|
|
<th class="head"><p>Meaning</p></th>
|
|||
|
|
</tr>
|
|||
|
|
</thead>
|
|||
|
|
<tbody>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_NOTE_EXIT</span></code></p></td>
|
|||
|
|
<td><p>the process has exited</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_NOTE_FORK</span></code></p></td>
|
|||
|
|
<td><p>the process has called <em>fork()</em></p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_NOTE_EXEC</span></code></p></td>
|
|||
|
|
<td><p>the process has executed a new process</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_NOTE_PCTRLMASK</span></code></p></td>
|
|||
|
|
<td><p>internal filter flag</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_NOTE_PDATAMASK</span></code></p></td>
|
|||
|
|
<td><p>internal filter flag</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_NOTE_TRACK</span></code></p></td>
|
|||
|
|
<td><p>follow a process across <em>fork()</em></p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_NOTE_CHILD</span></code></p></td>
|
|||
|
|
<td><p>returned on the child process for
|
|||
|
|
<em>NOTE_TRACK</em></p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_NOTE_TRACKERR</span></code></p></td>
|
|||
|
|
<td><p>unable to attach to a child</p></td>
|
|||
|
|
</tr>
|
|||
|
|
</tbody>
|
|||
|
|
</table>
|
|||
|
|
<p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_FILTER_NETDEV</span></code> filter flags (not available on Mac OS X):</p>
|
|||
|
|
<table class="docutils align-center">
|
|||
|
|
<colgroup>
|
|||
|
|
<col style="width: 39%" />
|
|||
|
|
<col style="width: 61%" />
|
|||
|
|
</colgroup>
|
|||
|
|
<thead>
|
|||
|
|
<tr class="row-odd"><th class="head"><p>Constant</p></th>
|
|||
|
|
<th class="head"><p>Meaning</p></th>
|
|||
|
|
</tr>
|
|||
|
|
</thead>
|
|||
|
|
<tbody>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_NOTE_LINKUP</span></code></p></td>
|
|||
|
|
<td><p>link is up</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_NOTE_LINKDOWN</span></code></p></td>
|
|||
|
|
<td><p>link is down</p></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">KQ_NOTE_LINKINV</span></code></p></td>
|
|||
|
|
<td><p>link state is invalid</p></td>
|
|||
|
|
</tr>
|
|||
|
|
</tbody>
|
|||
|
|
</table>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
<dl class="attribute">
|
|||
|
|
<dt id="select.kevent.data">
|
|||
|
|
<code class="descclassname">kevent.</code><code class="descname">data</code><a class="headerlink" href="#select.kevent.data" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>Filter specific data.</p>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
<dl class="attribute">
|
|||
|
|
<dt id="select.kevent.udata">
|
|||
|
|
<code class="descclassname">kevent.</code><code class="descname">udata</code><a class="headerlink" href="#select.kevent.udata" title="Permalink to this definition">¶</a></dt>
|
|||
|
|
<dd><p>User defined value.</p>
|
|||
|
|
</dd></dl>
|
|||
|
|
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
|
|||
|
|
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
<div class="sphinxsidebar" role="navigation" aria-label="main navigation">
|
|||
|
|
<div class="sphinxsidebarwrapper">
|
|||
|
|
<h3><a href="../contents.html">Table of Contents</a></h3>
|
|||
|
|
<ul>
|
|||
|
|
<li><a class="reference internal" href="#"><code class="xref py py-mod docutils literal notranslate"><span class="pre">select</span></code> — Waiting for I/O completion</a><ul>
|
|||
|
|
<li><a class="reference internal" href="#dev-poll-polling-objects"><code class="docutils literal notranslate"><span class="pre">/dev/poll</span></code> Polling Objects</a></li>
|
|||
|
|
<li><a class="reference internal" href="#edge-and-level-trigger-polling-epoll-objects">Edge and Level Trigger Polling (epoll) Objects</a></li>
|
|||
|
|
<li><a class="reference internal" href="#polling-objects">Polling Objects</a></li>
|
|||
|
|
<li><a class="reference internal" href="#kqueue-objects">Kqueue Objects</a></li>
|
|||
|
|
<li><a class="reference internal" href="#kevent-objects">Kevent Objects</a></li>
|
|||
|
|
</ul>
|
|||
|
|
</li>
|
|||
|
|
</ul>
|
|||
|
|
|
|||
|
|
<h4>Previous topic</h4>
|
|||
|
|
<p class="topless"><a href="ssl.html"
|
|||
|
|
title="previous chapter"><code class="xref py py-mod docutils literal notranslate"><span class="pre">ssl</span></code> — TLS/SSL wrapper for socket objects</a></p>
|
|||
|
|
<h4>Next topic</h4>
|
|||
|
|
<p class="topless"><a href="selectors.html"
|
|||
|
|
title="next chapter"><code class="xref py py-mod docutils literal notranslate"><span class="pre">selectors</span></code> — High-level I/O multiplexing</a></p>
|
|||
|
|
<div role="note" aria-label="source link">
|
|||
|
|
<h3>This Page</h3>
|
|||
|
|
<ul class="this-page-menu">
|
|||
|
|
<li><a href="../bugs.html">Report a Bug</a></li>
|
|||
|
|
<li>
|
|||
|
|
<a href="https://github.com/python/cpython/blob/3.7/Doc/library/select.rst"
|
|||
|
|
rel="nofollow">Show Source
|
|||
|
|
</a>
|
|||
|
|
</li>
|
|||
|
|
</ul>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
<div class="clearer"></div>
|
|||
|
|
</div>
|
|||
|
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|||
|
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<h3>Navigation</h3>
|
|||
|
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<ul>
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<li class="right" style="margin-right: 10px">
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<a href="../genindex.html" title="General Index"
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<li class="right" >
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|
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|
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<li class="right" >
|
|||
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|||
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