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<div class="section" id="module-pipes">
<span id="pipes-interface-to-shell-pipelines"></span><h1>33.10. <a class="reference internal" href="#module-pipes" title="pipes: A Python interface to Unix shell pipelines. (Unix)"><tt class="xref py py-mod docutils literal"><span class="pre">pipes</span></tt></a> — Interface to shell pipelines<a class="headerlink" href="#module-pipes" title="Permalink to this headline">¶</a></h1>
<p><em>Platforms: </em>Unix</p>
<p><strong>Source code:</strong> <a class="reference external" href="http://hg.python.org/cpython/file/3.2/Lib/pipes.py">Lib/pipes.py</a></p>
<hr class="docutils" />
<p>The <a class="reference internal" href="#module-pipes" title="pipes: A Python interface to Unix shell pipelines. (Unix)"><tt class="xref py py-mod docutils literal"><span class="pre">pipes</span></tt></a> module defines a class to abstract the concept of a <em>pipeline</em>
— a sequence of converters from one file to another.</p>
<p>Because the module uses <strong class="program">/bin/sh</strong> command lines, a POSIX or compatible
shell for <a class="reference internal" href="os.html#os.system" title="os.system"><tt class="xref py py-func docutils literal"><span class="pre">os.system()</span></tt></a> and <tt class="xref py py-func docutils literal"><span class="pre">os.popen()</span></tt> is required.</p>
<p>The <a class="reference internal" href="#module-pipes" title="pipes: A Python interface to Unix shell pipelines. (Unix)"><tt class="xref py py-mod docutils literal"><span class="pre">pipes</span></tt></a> module defines the following class:</p>
<dl class="class">
<dt id="pipes.Template">
<em class="property">class </em><tt class="descclassname">pipes.</tt><tt class="descname">Template</tt><a class="headerlink" href="#pipes.Template" title="Permalink to this definition">¶</a></dt>
<dd><p>An abstraction of a pipeline.</p>
</dd></dl>
<p>Example:</p>
<div class="highlight-python3"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">pipes</span>
<span class="gp">>>> </span><span class="n">t</span><span class="o">=</span><span class="n">pipes</span><span class="o">.</span><span class="n">Template</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">t</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="s">'tr a-z A-Z'</span><span class="p">,</span> <span class="s">'--'</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">f</span><span class="o">=</span><span class="n">t</span><span class="o">.</span><span class="n">open</span><span class="p">(</span><span class="s">'/tmp/1'</span><span class="p">,</span> <span class="s">'w'</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">f</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s">'hello world'</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">f</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
<span class="gp">>>> </span><span class="nb">open</span><span class="p">(</span><span class="s">'/tmp/1'</span><span class="p">)</span><span class="o">.</span><span class="n">read</span><span class="p">()</span>
<span class="go">'HELLO WORLD'</span>
</pre></div>
</div>
<div class="section" id="template-objects">
<span id="id1"></span><h2>33.10.1. Template Objects<a class="headerlink" href="#template-objects" title="Permalink to this headline">¶</a></h2>
<p>Template objects following methods:</p>
<dl class="method">
<dt id="pipes.Template.reset">
<tt class="descclassname">Template.</tt><tt class="descname">reset</tt><big>(</big><big>)</big><a class="headerlink" href="#pipes.Template.reset" title="Permalink to this definition">¶</a></dt>
<dd><p>Restore a pipeline template to its initial state.</p>
</dd></dl>
<dl class="method">
<dt id="pipes.Template.clone">
<tt class="descclassname">Template.</tt><tt class="descname">clone</tt><big>(</big><big>)</big><a class="headerlink" href="#pipes.Template.clone" title="Permalink to this definition">¶</a></dt>
<dd><p>Return a new, equivalent, pipeline template.</p>
</dd></dl>
<dl class="method">
<dt id="pipes.Template.debug">
<tt class="descclassname">Template.</tt><tt class="descname">debug</tt><big>(</big><em>flag</em><big>)</big><a class="headerlink" href="#pipes.Template.debug" title="Permalink to this definition">¶</a></dt>
<dd><p>If <em>flag</em> is true, turn debugging on. Otherwise, turn debugging off. When
debugging is on, commands to be executed are printed, and the shell is given
<tt class="docutils literal"><span class="pre">set</span> <span class="pre">-x</span></tt> command to be more verbose.</p>
</dd></dl>
<dl class="method">
<dt id="pipes.Template.append">
<tt class="descclassname">Template.</tt><tt class="descname">append</tt><big>(</big><em>cmd</em>, <em>kind</em><big>)</big><a class="headerlink" href="#pipes.Template.append" title="Permalink to this definition">¶</a></dt>
<dd><p>Append a new action at the end. The <em>cmd</em> variable must be a valid bourne shell
command. The <em>kind</em> variable consists of two letters.</p>
<p>The first letter can be either of <tt class="docutils literal"><span class="pre">'-'</span></tt> (which means the command reads its
standard input), <tt class="docutils literal"><span class="pre">'f'</span></tt> (which means the commands reads a given file on the
command line) or <tt class="docutils literal"><span class="pre">'.'</span></tt> (which means the commands reads no input, and hence
must be first.)</p>
<p>Similarly, the second letter can be either of <tt class="docutils literal"><span class="pre">'-'</span></tt> (which means the command
writes to standard output), <tt class="docutils literal"><span class="pre">'f'</span></tt> (which means the command writes a file on
the command line) or <tt class="docutils literal"><span class="pre">'.'</span></tt> (which means the command does not write anything,
and hence must be last.)</p>
</dd></dl>
<dl class="method">
<dt id="pipes.Template.prepend">
<tt class="descclassname">Template.</tt><tt class="descname">prepend</tt><big>(</big><em>cmd</em>, <em>kind</em><big>)</big><a class="headerlink" href="#pipes.Template.prepend" title="Permalink to this definition">¶</a></dt>
<dd><p>Add a new action at the beginning. See <a class="reference internal" href="#pipes.Template.append" title="pipes.Template.append"><tt class="xref py py-meth docutils literal"><span class="pre">append()</span></tt></a> for explanations of the
arguments.</p>
</dd></dl>
<dl class="method">
<dt id="pipes.Template.open">
<tt class="descclassname">Template.</tt><tt class="descname">open</tt><big>(</big><em>file</em>, <em>mode</em><big>)</big><a class="headerlink" href="#pipes.Template.open" title="Permalink to this definition">¶</a></dt>
<dd><p>Return a file-like object, open to <em>file</em>, but read from or written to by the
pipeline. Note that only one of <tt class="docutils literal"><span class="pre">'r'</span></tt>, <tt class="docutils literal"><span class="pre">'w'</span></tt> may be given.</p>
</dd></dl>
<dl class="method">
<dt id="pipes.Template.copy">
<tt class="descclassname">Template.</tt><tt class="descname">copy</tt><big>(</big><em>infile</em>, <em>outfile</em><big>)</big><a class="headerlink" href="#pipes.Template.copy" title="Permalink to this definition">¶</a></dt>
<dd><p>Copy <em>infile</em> to <em>outfile</em> through the pipe.</p>
</dd></dl>
</div>
</div>
</div>
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<h3><a href="../contents.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">33.10. <tt class="docutils literal"><span class="pre">pipes</span></tt> — Interface to shell pipelines</a><ul>
<li><a class="reference internal" href="#template-objects">33.10.1. Template Objects</a></li>
</ul>
</li>
</ul>
<h4>Previous topic</h4>
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title="previous chapter">33.9. <tt class="docutils literal docutils literal"><span class="pre">fcntl</span></tt> — The <tt class="docutils literal docutils literal"><span class="pre">fcntl()</span></tt> and <tt class="docutils literal docutils literal"><span class="pre">ioctl()</span></tt> system calls</a></p>
<h4>Next topic</h4>
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