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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="X-UA-Compatible" content="IE=Edge" /> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>36.11. pipes — Interface to shell pipelines — Python 2.7.18 documentation</title> <link rel="stylesheet" href="../_static/classic.css" type="text/css" /> <link rel="stylesheet" href="../_static/pygments.css" type="text/css" /> <script type="text/javascript" id="documentation_options" data-url_root="../" src="../_static/documentation_options.js"></script> <script type="text/javascript" src="../_static/jquery.js"></script> <script type="text/javascript" src="../_static/underscore.js"></script> <script type="text/javascript" src="../_static/doctools.js"></script> <script type="text/javascript" src="../_static/language_data.js"></script> <script type="text/javascript" src="../_static/sidebar.js"></script> <link rel="search" type="application/opensearchdescription+xml" title="Search within Python 2.7.18 documentation" href="../_static/opensearch.xml"/> <link rel="author" title="About these documents" href="../about.html" /> <link rel="index" title="Index" href="../genindex.html" /> <link rel="search" title="Search" href="../search.html" /> <link rel="copyright" title="Copyright" href="../copyright.html" /> <link rel="next" title="36.12. posixfile — File-like objects with locking support" href="posixfile.html" /> <link rel="prev" title="36.10. fcntl — The fcntl and ioctl system calls" href="fcntl.html" /> <link rel="shortcut icon" type="image/png" href="../_static/py.png" /> <link rel="canonical" href="file:///usr/share/doc/python2.7/html/library/pipes.html" /> <script type="text/javascript" src="../_static/copybutton.js"></script> </head><body> <div id="outdated-warning" style="padding: .5em; text-align: center; background-color: #FFBABA; color: #6A0E0E;"> This document is for an old version of Python that is <a href="https://devguide.python.org/devcycle/#end-of-life-branches">no longer supported</a>. You should install the python3 and python3-doc packages and read the <a href="file:///usr/share/doc/python3-doc/html/library/pipes.html"> Python documentation for the Python3 version packaged in this release</a>. </div> <div class="related" role="navigation" aria-label="related navigation"> <h3>Navigation</h3> <ul> <li class="right" style="margin-right: 10px"> <a href="../genindex.html" title="General Index" accesskey="I">index</a></li> <li class="right" > <a href="../py-modindex.html" title="Python Module Index" >modules</a> |</li> <li class="right" > <a href="posixfile.html" title="36.12. posixfile — File-like objects with locking support" accesskey="N">next</a> |</li> <li class="right" > <a href="fcntl.html" title="36.10. fcntl — The fcntl and ioctl system calls" accesskey="P">previous</a> |</li> <li><img src="../_static/py.png" alt="" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="https://www.python.org/">Python</a> »</li> <li> <a href="../index.html">Python 2.7.18 documentation</a> » </li> <li class="nav-item nav-item-1"><a href="index.html" >The Python Standard Library</a> »</li> <li class="nav-item nav-item-2"><a href="unix.html" accesskey="U">36. Unix Specific Services</a> »</li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body" role="main"> <div class="section" id="module-pipes"> <span id="pipes-interface-to-shell-pipelines"></span><h1>36.11. <a class="reference internal" href="#module-pipes" title="pipes: A Python interface to Unix shell pipelines. (Unix)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">pipes</span></code></a> — Interface to shell pipelines<a class="headerlink" href="#module-pipes" title="Permalink to this headline">¶</a></h1> <p><strong>Source code:</strong> <a class="reference external" href="https://github.com/python/cpython/tree/2.7/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)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">pipes</span></code></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"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.system()</span></code></a> and <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> is required.</p> <dl class="class"> <dt id="pipes.Template"> <em class="property">class </em><code class="descclassname">pipes.</code><code class="descname">Template</code><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-default notranslate"><div class="highlight"><pre><span></span><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="s1">'tr a-z A-Z'</span><span class="p">,</span> <span class="s1">'--'</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="s1">'pipefile'</span><span class="p">,</span> <span class="s1">'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="s1">'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="s1">'pipefile'</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> <dl class="function"> <dt id="pipes.quote"> <code class="descclassname">pipes.</code><code class="descname">quote</code><span class="sig-paren">(</span><em>s</em><span class="sig-paren">)</span><a class="headerlink" href="#pipes.quote" title="Permalink to this definition">¶</a></dt> <dd><div class="deprecated"> <p><span class="versionmodified">Deprecated since version 2.7: </span>Prior to Python 2.7, this function was not publicly documented. It is finally exposed publicly in Python 3.3 as the <code class="xref py py-func docutils literal notranslate"><span class="pre">quote</span></code> function in the <a class="reference internal" href="shlex.html#module-shlex" title="shlex: Simple lexical analysis for Unix shell-like languages."><code class="xref py py-mod docutils literal notranslate"><span class="pre">shlex</span></code></a> module.</p> </div> <p>Return a shell-escaped version of the string <em>s</em>. The returned value is a string that can safely be used as one token in a shell command line, for cases where you cannot use a list.</p> <p>This idiom would be unsafe:</p> <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">filename</span> <span class="o">=</span> <span class="s1">'somefile; rm -rf ~'</span> <span class="gp">>>> </span><span class="n">command</span> <span class="o">=</span> <span class="s1">'ls -l </span><span class="si">{}</span><span class="s1">'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">filename</span><span class="p">)</span> <span class="gp">>>> </span><span class="nb">print</span> <span class="n">command</span> <span class="c1"># executed by a shell: boom!</span> <span class="go">ls -l somefile; rm -rf ~</span> </pre></div> </div> <p><a class="reference internal" href="#pipes.quote" title="pipes.quote"><code class="xref py py-func docutils literal notranslate"><span class="pre">quote()</span></code></a> lets you plug the security hole:</p> <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">command</span> <span class="o">=</span> <span class="s1">'ls -l </span><span class="si">{}</span><span class="s1">'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">quote</span><span class="p">(</span><span class="n">filename</span><span class="p">))</span> <span class="gp">>>> </span><span class="nb">print</span> <span class="n">command</span> <span class="go">ls -l 'somefile; rm -rf ~'</span> <span class="gp">>>> </span><span class="n">remote_command</span> <span class="o">=</span> <span class="s1">'ssh home </span><span class="si">{}</span><span class="s1">'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">quote</span><span class="p">(</span><span class="n">command</span><span class="p">))</span> <span class="gp">>>> </span><span class="nb">print</span> <span class="n">remote_command</span> <span class="go">ssh home 'ls -l '"'"'somefile; rm -rf ~'"'"''</span> </pre></div> </div> <p>The quoting is compatible with UNIX shells and with <a class="reference internal" href="shlex.html#shlex.split" title="shlex.split"><code class="xref py py-func docutils literal notranslate"><span class="pre">shlex.split()</span></code></a>:</p> <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">remote_command</span> <span class="o">=</span> <span class="n">shlex</span><span class="o">.</span><span class="n">split</span><span class="p">(</span><span class="n">remote_command</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">remote_command</span> <span class="go">['ssh', 'home', "ls -l 'somefile; rm -rf ~'"]</span> <span class="gp">>>> </span><span class="n">command</span> <span class="o">=</span> <span class="n">shlex</span><span class="o">.</span><span class="n">split</span><span class="p">(</span><span class="n">remote_command</span><span class="p">[</span><span class="o">-</span><span class="mi">1</span><span class="p">])</span> <span class="gp">>>> </span><span class="n">command</span> <span class="go">['ls', '-l', 'somefile; rm -rf ~']</span> </pre></div> </div> </dd></dl> <div class="section" id="template-objects"> <span id="id1"></span><h2>36.11.1. 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"> <code class="descclassname">Template.</code><code class="descname">reset</code><span class="sig-paren">(</span><span class="sig-paren">)</span><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"> <code class="descclassname">Template.</code><code class="descname">clone</code><span class="sig-paren">(</span><span class="sig-paren">)</span><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"> <code class="descclassname">Template.</code><code class="descname">debug</code><span class="sig-paren">(</span><em>flag</em><span class="sig-paren">)</span><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 <code class="docutils literal notranslate"><span class="pre">set</span> <span class="pre">-x</span></code> command to be more verbose.</p> </dd></dl> <dl class="method"> <dt id="pipes.Template.append"> <code class="descclassname">Template.</code><code class="descname">append</code><span class="sig-paren">(</span><em>cmd</em>, <em>kind</em><span class="sig-paren">)</span><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 <code class="docutils literal notranslate"><span class="pre">'-'</span></code> (which means the command reads its standard input), <code class="docutils literal notranslate"><span class="pre">'f'</span></code> (which means the commands reads a given file on the command line) or <code class="docutils literal notranslate"><span class="pre">'.'</span></code> (which means the commands reads no input, and hence must be first.)</p> <p>Similarly, the second letter can be either of <code class="docutils literal notranslate"><span class="pre">'-'</span></code> (which means the command writes to standard output), <code class="docutils literal notranslate"><span class="pre">'f'</span></code> (which means the command writes a file on the command line) or <code class="docutils literal notranslate"><span class="pre">'.'</span></code> (which means the command does not write anything, and hence must be last.)</p> </dd></dl> <dl class="method"> <dt id="pipes.Template.prepend"> <code class="descclassname">Template.</code><code class="descname">prepend</code><span class="sig-paren">(</span><em>cmd</em>, <em>kind</em><span class="sig-paren">)</span><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"><code class="xref py py-meth docutils literal notranslate"><span class="pre">append()</span></code></a> for explanations of the arguments.</p> </dd></dl> <dl class="method"> <dt id="pipes.Template.open"> <code class="descclassname">Template.</code><code class="descname">open</code><span class="sig-paren">(</span><em>file</em>, <em>mode</em><span class="sig-paren">)</span><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 <code class="docutils literal notranslate"><span class="pre">'r'</span></code>, <code class="docutils literal notranslate"><span class="pre">'w'</span></code> may be given.</p> </dd></dl> <dl class="method"> <dt id="pipes.Template.copy"> <code class="descclassname">Template.</code><code class="descname">copy</code><span class="sig-paren">(</span><em>infile</em>, <em>outfile</em><span class="sig-paren">)</span><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> </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="#">36.11. <code class="docutils literal notranslate"><span class="pre">pipes</span></code> — Interface to shell pipelines</a><ul> <li><a class="reference internal" href="#template-objects">36.11.1. Template Objects</a></li> </ul> </li> </ul> <h4>Previous topic</h4> <p class="topless"><a href="fcntl.html" title="previous chapter">36.10. <code class="docutils literal notranslate"><span class="pre">fcntl</span></code> — The <code class="docutils literal notranslate"><span class="pre">fcntl</span></code> and <code class="docutils literal notranslate"><span class="pre">ioctl</span></code> system calls</a></p> <h4>Next topic</h4> <p class="topless"><a href="posixfile.html" title="next chapter">36.12. <code class="docutils literal notranslate"><span class="pre">posixfile</span></code> — File-like objects with locking support</a></p> <div role="note" aria-label="source link"> <h3>This Page</h3> <ul class="this-page-menu"> <li><a href="../_sources/library/pipes.rst.txt" rel="nofollow">Show Source</a></li> </ul> </div> <div id="searchbox" style="display: none" role="search"> <h3>Quick search</h3> <div class="searchformwrapper"> <form class="search" action="../search.html" method="get"> <input type="text" name="q" /> <input type="submit" value="Go" /> <input type="hidden" name="check_keywords" value="yes" /> <input type="hidden" name="area" value="default" /> </form> </div> </div> <script type="text/javascript">$('#searchbox').show(0);</script> </div> </div> <div class="clearer"></div> </div> <div class="related" role="navigation" aria-label="related navigation"> <h3>Navigation</h3> <ul> <li class="right" style="margin-right: 10px"> <a href="../genindex.html" title="General Index" >index</a></li> <li class="right" > <a href="../py-modindex.html" title="Python Module Index" >modules</a> |</li> <li class="right" > <a href="posixfile.html" title="36.12. posixfile — File-like objects with locking support" >next</a> |</li> <li class="right" > <a href="fcntl.html" title="36.10. fcntl — The fcntl and ioctl system calls" >previous</a> |</li> <li><img src="../_static/py.png" alt="" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="https://www.python.org/">Python</a> »</li> <li> <a href="../index.html">Python 2.7.18 documentation</a> » </li> <li class="nav-item nav-item-1"><a href="index.html" >The Python Standard Library</a> »</li> <li class="nav-item nav-item-2"><a href="unix.html" >36. 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