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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>17.5. subprocess — Subprocess management — Python 3.6.7 documentation</title> <link rel="stylesheet" href="../_static/pydoctheme.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/sidebar.js"></script> <link rel="search" type="application/opensearchdescription+xml" title="Search within Python 3.6.7 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="17.6. sched — Event scheduler" href="sched.html" /> <link rel="prev" title="17.4. concurrent.futures — Launching parallel tasks" href="concurrent.futures.html" /> <link rel="shortcut icon" type="image/png" href="../_static/py.png" /> <link rel="canonical" href="https://docs.python.org/3/library/subprocess.html" /> <script type="text/javascript" src="../_static/copybutton.js"></script> </head><body> <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="sched.html" title="17.6. sched — Event scheduler" accesskey="N">next</a> |</li> <li class="right" > <a href="concurrent.futures.html" title="17.4. concurrent.futures — Launching parallel tasks" 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">3.6.7 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="concurrency.html" accesskey="U">17. Concurrent Execution</a> »</li> <li class="right"> <div class="inline-search" style="display: none" role="search"> <form class="inline-search" action="../search.html" method="get"> <input placeholder="Quick search" 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> <script type="text/javascript">$('.inline-search').show(0);</script> | </li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body" role="main"> <div class="section" id="module-subprocess"> <span id="subprocess-subprocess-management"></span><h1>17.5. <a class="reference internal" href="#module-subprocess" title="subprocess: Subprocess management."><code class="xref py py-mod docutils literal notranslate"><span class="pre">subprocess</span></code></a> — Subprocess management<a class="headerlink" href="#module-subprocess" title="Permalink to this headline">¶</a></h1> <p><strong>Source code:</strong> <a class="reference external" href="https://github.com/python/cpython/tree/3.6/Lib/subprocess.py">Lib/subprocess.py</a></p> <hr class="docutils" /> <p>The <a class="reference internal" href="#module-subprocess" title="subprocess: Subprocess management."><code class="xref py py-mod docutils literal notranslate"><span class="pre">subprocess</span></code></a> module allows you to spawn new processes, connect to their input/output/error pipes, and obtain their return codes. This module intends to replace several older modules and functions:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">os</span><span class="o">.</span><span class="n">system</span> <span class="n">os</span><span class="o">.</span><span class="n">spawn</span><span class="o">*</span> </pre></div> </div> <p>Information about how the <a class="reference internal" href="#module-subprocess" title="subprocess: Subprocess management."><code class="xref py py-mod docutils literal notranslate"><span class="pre">subprocess</span></code></a> module can be used to replace these modules and functions can be found in the following sections.</p> <div class="admonition seealso"> <p class="first admonition-title">See also</p> <p class="last"><span class="target" id="index-0"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0324"><strong>PEP 324</strong></a> – PEP proposing the subprocess module</p> </div> <div class="section" id="using-the-subprocess-module"> <h2>17.5.1. Using the <a class="reference internal" href="#module-subprocess" title="subprocess: Subprocess management."><code class="xref py py-mod docutils literal notranslate"><span class="pre">subprocess</span></code></a> Module<a class="headerlink" href="#using-the-subprocess-module" title="Permalink to this headline">¶</a></h2> <p>The recommended approach to invoking subprocesses is to use the <a class="reference internal" href="#subprocess.run" title="subprocess.run"><code class="xref py py-func docutils literal notranslate"><span class="pre">run()</span></code></a> function for all use cases it can handle. For more advanced use cases, the underlying <a class="reference internal" href="#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">Popen</span></code></a> interface can be used directly.</p> <p>The <a class="reference internal" href="#subprocess.run" title="subprocess.run"><code class="xref py py-func docutils literal notranslate"><span class="pre">run()</span></code></a> function was added in Python 3.5; if you need to retain compatibility with older versions, see the <a class="reference internal" href="#call-function-trio"><span class="std std-ref">Older high-level API</span></a> section.</p> <dl class="function"> <dt id="subprocess.run"> <code class="descclassname">subprocess.</code><code class="descname">run</code><span class="sig-paren">(</span><em>args</em>, <em>*</em>, <em>stdin=None</em>, <em>input=None</em>, <em>stdout=None</em>, <em>stderr=None</em>, <em>shell=False</em>, <em>cwd=None</em>, <em>timeout=None</em>, <em>check=False</em>, <em>encoding=None</em>, <em>errors=None</em>, <em>env=None</em><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.run" title="Permalink to this definition">¶</a></dt> <dd><p>Run the command described by <em>args</em>. Wait for command to complete, then return a <a class="reference internal" href="#subprocess.CompletedProcess" title="subprocess.CompletedProcess"><code class="xref py py-class docutils literal notranslate"><span class="pre">CompletedProcess</span></code></a> instance.</p> <p>The arguments shown above are merely the most common ones, described below in <a class="reference internal" href="#frequently-used-arguments"><span class="std std-ref">Frequently Used Arguments</span></a> (hence the use of keyword-only notation in the abbreviated signature). The full function signature is largely the same as that of the <a class="reference internal" href="#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">Popen</span></code></a> constructor - apart from <em>timeout</em>, <em>input</em> and <em>check</em>, all the arguments to this function are passed through to that interface.</p> <p>This does not capture stdout or stderr by default. To do so, pass <a class="reference internal" href="#subprocess.PIPE" title="subprocess.PIPE"><code class="xref py py-data docutils literal notranslate"><span class="pre">PIPE</span></code></a> for the <em>stdout</em> and/or <em>stderr</em> arguments.</p> <p>The <em>timeout</em> argument is passed to <a class="reference internal" href="#subprocess.Popen.communicate" title="subprocess.Popen.communicate"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Popen.communicate()</span></code></a>. If the timeout expires, the child process will be killed and waited for. The <a class="reference internal" href="#subprocess.TimeoutExpired" title="subprocess.TimeoutExpired"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TimeoutExpired</span></code></a> exception will be re-raised after the child process has terminated.</p> <p>The <em>input</em> argument is passed to <a class="reference internal" href="#subprocess.Popen.communicate" title="subprocess.Popen.communicate"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Popen.communicate()</span></code></a> and thus to the subprocess’s stdin. If used it must be a byte sequence, or a string if <em>encoding</em> or <em>errors</em> is specified or <em>universal_newlines</em> is true. When used, the internal <a class="reference internal" href="#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">Popen</span></code></a> object is automatically created with <code class="docutils literal notranslate"><span class="pre">stdin=PIPE</span></code>, and the <em>stdin</em> argument may not be used as well.</p> <p>If <em>check</em> is true, and the process exits with a non-zero exit code, a <a class="reference internal" href="#subprocess.CalledProcessError" title="subprocess.CalledProcessError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">CalledProcessError</span></code></a> exception will be raised. Attributes of that exception hold the arguments, the exit code, and stdout and stderr if they were captured.</p> <p>If <em>encoding</em> or <em>errors</em> are specified, or <em>universal_newlines</em> is true, file objects for stdin, stdout and stderr are opened in text mode using the specified <em>encoding</em> and <em>errors</em> or the <a class="reference internal" href="io.html#io.TextIOWrapper" title="io.TextIOWrapper"><code class="xref py py-class docutils literal notranslate"><span class="pre">io.TextIOWrapper</span></code></a> default. Otherwise, file objects are opened in binary mode.</p> <p>If <em>env</em> is not <code class="docutils literal notranslate"><span class="pre">None</span></code>, it must be a mapping that defines the environment variables for the new process; these are used instead of the default behavior of inheriting the current process’ environment. It is passed directly to <a class="reference internal" href="#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">Popen</span></code></a>.</p> <p>Examples:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">subprocess</span><span class="o">.</span><span class="n">run</span><span class="p">([</span><span class="s2">"ls"</span><span class="p">,</span> <span class="s2">"-l"</span><span class="p">])</span> <span class="c1"># doesn't capture output</span> <span class="go">CompletedProcess(args=['ls', '-l'], returncode=0)</span> <span class="gp">>>> </span><span class="n">subprocess</span><span class="o">.</span><span class="n">run</span><span class="p">(</span><span class="s2">"exit 1"</span><span class="p">,</span> <span class="n">shell</span><span class="o">=</span><span class="kc">True</span><span class="p">,</span> <span class="n">check</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span> <span class="gt">Traceback (most recent call last):</span> <span class="c">...</span> <span class="gr">subprocess.CalledProcessError</span>: <span class="n">Command 'exit 1' returned non-zero exit status 1</span> <span class="gp">>>> </span><span class="n">subprocess</span><span class="o">.</span><span class="n">run</span><span class="p">([</span><span class="s2">"ls"</span><span class="p">,</span> <span class="s2">"-l"</span><span class="p">,</span> <span class="s2">"/dev/null"</span><span class="p">],</span> <span class="n">stdout</span><span class="o">=</span><span class="n">subprocess</span><span class="o">.</span><span class="n">PIPE</span><span class="p">)</span> <span class="go">CompletedProcess(args=['ls', '-l', '/dev/null'], returncode=0,</span> <span class="go">stdout=b'crw-rw-rw- 1 root root 1, 3 Jan 23 16:23 /dev/null\n')</span> </pre></div> </div> <div class="versionadded"> <p><span class="versionmodified">New in version 3.5.</span></p> </div> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.6: </span>Added <em>encoding</em> and <em>errors</em> parameters</p> </div> </dd></dl> <dl class="class"> <dt id="subprocess.CompletedProcess"> <em class="property">class </em><code class="descclassname">subprocess.</code><code class="descname">CompletedProcess</code><a class="headerlink" href="#subprocess.CompletedProcess" title="Permalink to this definition">¶</a></dt> <dd><p>The return value from <a class="reference internal" href="#subprocess.run" title="subprocess.run"><code class="xref py py-func docutils literal notranslate"><span class="pre">run()</span></code></a>, representing a process that has finished.</p> <dl class="attribute"> <dt id="subprocess.CompletedProcess.args"> <code class="descname">args</code><a class="headerlink" href="#subprocess.CompletedProcess.args" title="Permalink to this definition">¶</a></dt> <dd><p>The arguments used to launch the process. This may be a list or a string.</p> </dd></dl> <dl class="attribute"> <dt id="subprocess.CompletedProcess.returncode"> <code class="descname">returncode</code><a class="headerlink" href="#subprocess.CompletedProcess.returncode" title="Permalink to this definition">¶</a></dt> <dd><p>Exit status of the child process. Typically, an exit status of 0 indicates that it ran successfully.</p> <p>A negative value <code class="docutils literal notranslate"><span class="pre">-N</span></code> indicates that the child was terminated by signal <code class="docutils literal notranslate"><span class="pre">N</span></code> (POSIX only).</p> </dd></dl> <dl class="attribute"> <dt id="subprocess.CompletedProcess.stdout"> <code class="descname">stdout</code><a class="headerlink" href="#subprocess.CompletedProcess.stdout" title="Permalink to this definition">¶</a></dt> <dd><p>Captured stdout from the child process. A bytes sequence, or a string if <a class="reference internal" href="#subprocess.run" title="subprocess.run"><code class="xref py py-func docutils literal notranslate"><span class="pre">run()</span></code></a> was called with an encoding or errors. <code class="docutils literal notranslate"><span class="pre">None</span></code> if stdout was not captured.</p> <p>If you ran the process with <code class="docutils literal notranslate"><span class="pre">stderr=subprocess.STDOUT</span></code>, stdout and stderr will be combined in this attribute, and <a class="reference internal" href="#subprocess.CompletedProcess.stderr" title="subprocess.CompletedProcess.stderr"><code class="xref py py-attr docutils literal notranslate"><span class="pre">stderr</span></code></a> will be <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p> </dd></dl> <dl class="attribute"> <dt id="subprocess.CompletedProcess.stderr"> <code class="descname">stderr</code><a class="headerlink" href="#subprocess.CompletedProcess.stderr" title="Permalink to this definition">¶</a></dt> <dd><p>Captured stderr from the child process. A bytes sequence, or a string if <a class="reference internal" href="#subprocess.run" title="subprocess.run"><code class="xref py py-func docutils literal notranslate"><span class="pre">run()</span></code></a> was called with an encoding or errors. <code class="docutils literal notranslate"><span class="pre">None</span></code> if stderr was not captured.</p> </dd></dl> <dl class="method"> <dt id="subprocess.CompletedProcess.check_returncode"> <code class="descname">check_returncode</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.CompletedProcess.check_returncode" title="Permalink to this definition">¶</a></dt> <dd><p>If <a class="reference internal" href="#subprocess.CompletedProcess.returncode" title="subprocess.CompletedProcess.returncode"><code class="xref py py-attr docutils literal notranslate"><span class="pre">returncode</span></code></a> is non-zero, raise a <a class="reference internal" href="#subprocess.CalledProcessError" title="subprocess.CalledProcessError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">CalledProcessError</span></code></a>.</p> </dd></dl> <div class="versionadded"> <p><span class="versionmodified">New in version 3.5.</span></p> </div> </dd></dl> <dl class="data"> <dt id="subprocess.DEVNULL"> <code class="descclassname">subprocess.</code><code class="descname">DEVNULL</code><a class="headerlink" href="#subprocess.DEVNULL" title="Permalink to this definition">¶</a></dt> <dd><p>Special value that can be used as the <em>stdin</em>, <em>stdout</em> or <em>stderr</em> argument to <a class="reference internal" href="#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">Popen</span></code></a> and indicates that the special file <a class="reference internal" href="os.html#os.devnull" title="os.devnull"><code class="xref py py-data docutils literal notranslate"><span class="pre">os.devnull</span></code></a> will be used.</p> <div class="versionadded"> <p><span class="versionmodified">New in version 3.3.</span></p> </div> </dd></dl> <dl class="data"> <dt id="subprocess.PIPE"> <code class="descclassname">subprocess.</code><code class="descname">PIPE</code><a class="headerlink" href="#subprocess.PIPE" title="Permalink to this definition">¶</a></dt> <dd><p>Special value that can be used as the <em>stdin</em>, <em>stdout</em> or <em>stderr</em> argument to <a class="reference internal" href="#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">Popen</span></code></a> and indicates that a pipe to the standard stream should be opened. Most useful with <a class="reference internal" href="#subprocess.Popen.communicate" title="subprocess.Popen.communicate"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Popen.communicate()</span></code></a>.</p> </dd></dl> <dl class="data"> <dt id="subprocess.STDOUT"> <code class="descclassname">subprocess.</code><code class="descname">STDOUT</code><a class="headerlink" href="#subprocess.STDOUT" title="Permalink to this definition">¶</a></dt> <dd><p>Special value that can be used as the <em>stderr</em> argument to <a class="reference internal" href="#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">Popen</span></code></a> and indicates that standard error should go into the same handle as standard output.</p> </dd></dl> <dl class="exception"> <dt id="subprocess.SubprocessError"> <em class="property">exception </em><code class="descclassname">subprocess.</code><code class="descname">SubprocessError</code><a class="headerlink" href="#subprocess.SubprocessError" title="Permalink to this definition">¶</a></dt> <dd><p>Base class for all other exceptions from this module.</p> <div class="versionadded"> <p><span class="versionmodified">New in version 3.3.</span></p> </div> </dd></dl> <dl class="exception"> <dt id="subprocess.TimeoutExpired"> <em class="property">exception </em><code class="descclassname">subprocess.</code><code class="descname">TimeoutExpired</code><a class="headerlink" href="#subprocess.TimeoutExpired" title="Permalink to this definition">¶</a></dt> <dd><p>Subclass of <a class="reference internal" href="#subprocess.SubprocessError" title="subprocess.SubprocessError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">SubprocessError</span></code></a>, raised when a timeout expires while waiting for a child process.</p> <dl class="attribute"> <dt id="subprocess.TimeoutExpired.cmd"> <code class="descname">cmd</code><a class="headerlink" href="#subprocess.TimeoutExpired.cmd" title="Permalink to this definition">¶</a></dt> <dd><p>Command that was used to spawn the child process.</p> </dd></dl> <dl class="attribute"> <dt id="subprocess.TimeoutExpired.timeout"> <code class="descname">timeout</code><a class="headerlink" href="#subprocess.TimeoutExpired.timeout" title="Permalink to this definition">¶</a></dt> <dd><p>Timeout in seconds.</p> </dd></dl> <dl class="attribute"> <dt id="subprocess.TimeoutExpired.output"> <code class="descname">output</code><a class="headerlink" href="#subprocess.TimeoutExpired.output" title="Permalink to this definition">¶</a></dt> <dd><p>Output of the child process if it was captured by <a class="reference internal" href="#subprocess.run" title="subprocess.run"><code class="xref py py-func docutils literal notranslate"><span class="pre">run()</span></code></a> or <a class="reference internal" href="#subprocess.check_output" title="subprocess.check_output"><code class="xref py py-func docutils literal notranslate"><span class="pre">check_output()</span></code></a>. Otherwise, <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p> </dd></dl> <dl class="attribute"> <dt id="subprocess.TimeoutExpired.stdout"> <code class="descname">stdout</code><a class="headerlink" href="#subprocess.TimeoutExpired.stdout" title="Permalink to this definition">¶</a></dt> <dd><p>Alias for output, for symmetry with <a class="reference internal" href="#subprocess.TimeoutExpired.stderr" title="subprocess.TimeoutExpired.stderr"><code class="xref py py-attr docutils literal notranslate"><span class="pre">stderr</span></code></a>.</p> </dd></dl> <dl class="attribute"> <dt id="subprocess.TimeoutExpired.stderr"> <code class="descname">stderr</code><a class="headerlink" href="#subprocess.TimeoutExpired.stderr" title="Permalink to this definition">¶</a></dt> <dd><p>Stderr output of the child process if it was captured by <a class="reference internal" href="#subprocess.run" title="subprocess.run"><code class="xref py py-func docutils literal notranslate"><span class="pre">run()</span></code></a>. Otherwise, <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p> </dd></dl> <div class="versionadded"> <p><span class="versionmodified">New in version 3.3.</span></p> </div> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.5: </span><em>stdout</em> and <em>stderr</em> attributes added</p> </div> </dd></dl> <dl class="exception"> <dt id="subprocess.CalledProcessError"> <em class="property">exception </em><code class="descclassname">subprocess.</code><code class="descname">CalledProcessError</code><a class="headerlink" href="#subprocess.CalledProcessError" title="Permalink to this definition">¶</a></dt> <dd><p>Subclass of <a class="reference internal" href="#subprocess.SubprocessError" title="subprocess.SubprocessError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">SubprocessError</span></code></a>, raised when a process run by <a class="reference internal" href="#subprocess.check_call" title="subprocess.check_call"><code class="xref py py-func docutils literal notranslate"><span class="pre">check_call()</span></code></a> or <a class="reference internal" href="#subprocess.check_output" title="subprocess.check_output"><code class="xref py py-func docutils literal notranslate"><span class="pre">check_output()</span></code></a> returns a non-zero exit status.</p> <dl class="attribute"> <dt id="subprocess.CalledProcessError.returncode"> <code class="descname">returncode</code><a class="headerlink" href="#subprocess.CalledProcessError.returncode" title="Permalink to this definition">¶</a></dt> <dd><p>Exit status of the child process. If the process exited due to a signal, this will be the negative signal number.</p> </dd></dl> <dl class="attribute"> <dt id="subprocess.CalledProcessError.cmd"> <code class="descname">cmd</code><a class="headerlink" href="#subprocess.CalledProcessError.cmd" title="Permalink to this definition">¶</a></dt> <dd><p>Command that was used to spawn the child process.</p> </dd></dl> <dl class="attribute"> <dt id="subprocess.CalledProcessError.output"> <code class="descname">output</code><a class="headerlink" href="#subprocess.CalledProcessError.output" title="Permalink to this definition">¶</a></dt> <dd><p>Output of the child process if it was captured by <a class="reference internal" href="#subprocess.run" title="subprocess.run"><code class="xref py py-func docutils literal notranslate"><span class="pre">run()</span></code></a> or <a class="reference internal" href="#subprocess.check_output" title="subprocess.check_output"><code class="xref py py-func docutils literal notranslate"><span class="pre">check_output()</span></code></a>. Otherwise, <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p> </dd></dl> <dl class="attribute"> <dt id="subprocess.CalledProcessError.stdout"> <code class="descname">stdout</code><a class="headerlink" href="#subprocess.CalledProcessError.stdout" title="Permalink to this definition">¶</a></dt> <dd><p>Alias for output, for symmetry with <a class="reference internal" href="#subprocess.CalledProcessError.stderr" title="subprocess.CalledProcessError.stderr"><code class="xref py py-attr docutils literal notranslate"><span class="pre">stderr</span></code></a>.</p> </dd></dl> <dl class="attribute"> <dt id="subprocess.CalledProcessError.stderr"> <code class="descname">stderr</code><a class="headerlink" href="#subprocess.CalledProcessError.stderr" title="Permalink to this definition">¶</a></dt> <dd><p>Stderr output of the child process if it was captured by <a class="reference internal" href="#subprocess.run" title="subprocess.run"><code class="xref py py-func docutils literal notranslate"><span class="pre">run()</span></code></a>. Otherwise, <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p> </dd></dl> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.5: </span><em>stdout</em> and <em>stderr</em> attributes added</p> </div> </dd></dl> <div class="section" id="frequently-used-arguments"> <span id="id1"></span><h3>17.5.1.1. Frequently Used Arguments<a class="headerlink" href="#frequently-used-arguments" title="Permalink to this headline">¶</a></h3> <p>To support a wide variety of use cases, the <a class="reference internal" href="#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">Popen</span></code></a> constructor (and the convenience functions) accept a large number of optional arguments. For most typical use cases, many of these arguments can be safely left at their default values. The arguments that are most commonly needed are:</p> <blockquote> <div><p><em>args</em> is required for all calls and should be a string, or a sequence of program arguments. Providing a sequence of arguments is generally preferred, as it allows the module to take care of any required escaping and quoting of arguments (e.g. to permit spaces in file names). If passing a single string, either <em>shell</em> must be <a class="reference internal" href="constants.html#True" title="True"><code class="xref py py-const docutils literal notranslate"><span class="pre">True</span></code></a> (see below) or else the string must simply name the program to be executed without specifying any arguments.</p> <p><em>stdin</em>, <em>stdout</em> and <em>stderr</em> specify the executed program’s standard input, standard output and standard error file handles, respectively. Valid values are <a class="reference internal" href="#subprocess.PIPE" title="subprocess.PIPE"><code class="xref py py-data docutils literal notranslate"><span class="pre">PIPE</span></code></a>, <a class="reference internal" href="#subprocess.DEVNULL" title="subprocess.DEVNULL"><code class="xref py py-data docutils literal notranslate"><span class="pre">DEVNULL</span></code></a>, an existing file descriptor (a positive integer), an existing file object, and <code class="docutils literal notranslate"><span class="pre">None</span></code>. <a class="reference internal" href="#subprocess.PIPE" title="subprocess.PIPE"><code class="xref py py-data docutils literal notranslate"><span class="pre">PIPE</span></code></a> indicates that a new pipe to the child should be created. <a class="reference internal" href="#subprocess.DEVNULL" title="subprocess.DEVNULL"><code class="xref py py-data docutils literal notranslate"><span class="pre">DEVNULL</span></code></a> indicates that the special file <a class="reference internal" href="os.html#os.devnull" title="os.devnull"><code class="xref py py-data docutils literal notranslate"><span class="pre">os.devnull</span></code></a> will be used. With the default settings of <code class="docutils literal notranslate"><span class="pre">None</span></code>, no redirection will occur; the child’s file handles will be inherited from the parent. Additionally, <em>stderr</em> can be <a class="reference internal" href="#subprocess.STDOUT" title="subprocess.STDOUT"><code class="xref py py-data docutils literal notranslate"><span class="pre">STDOUT</span></code></a>, which indicates that the stderr data from the child process should be captured into the same file handle as for <em>stdout</em>.</p> <p id="index-1">If <em>encoding</em> or <em>errors</em> are specified, or <em>universal_newlines</em> is true, the file objects <em>stdin</em>, <em>stdout</em> and <em>stderr</em> will be opened in text mode using the <em>encoding</em> and <em>errors</em> specified in the call or the defaults for <a class="reference internal" href="io.html#io.TextIOWrapper" title="io.TextIOWrapper"><code class="xref py py-class docutils literal notranslate"><span class="pre">io.TextIOWrapper</span></code></a>.</p> <p>For <em>stdin</em>, line ending characters <code class="docutils literal notranslate"><span class="pre">'\n'</span></code> in the input will be converted to the default line separator <a class="reference internal" href="os.html#os.linesep" title="os.linesep"><code class="xref py py-data docutils literal notranslate"><span class="pre">os.linesep</span></code></a>. For <em>stdout</em> and <em>stderr</em>, all line endings in the output will be converted to <code class="docutils literal notranslate"><span class="pre">'\n'</span></code>. For more information see the documentation of the <a class="reference internal" href="io.html#io.TextIOWrapper" title="io.TextIOWrapper"><code class="xref py py-class docutils literal notranslate"><span class="pre">io.TextIOWrapper</span></code></a> class when the <em>newline</em> argument to its constructor is <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p> <p>If text mode is not used, <em>stdin</em>, <em>stdout</em> and <em>stderr</em> will be opened as binary streams. No encoding or line ending conversion is performed.</p> <div class="versionadded"> <p><span class="versionmodified">New in version 3.6: </span>Added <em>encoding</em> and <em>errors</em> parameters.</p> </div> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">The newlines attribute of the file objects <a class="reference internal" href="#subprocess.Popen.stdin" title="subprocess.Popen.stdin"><code class="xref py py-attr docutils literal notranslate"><span class="pre">Popen.stdin</span></code></a>, <a class="reference internal" href="#subprocess.Popen.stdout" title="subprocess.Popen.stdout"><code class="xref py py-attr docutils literal notranslate"><span class="pre">Popen.stdout</span></code></a> and <a class="reference internal" href="#subprocess.Popen.stderr" title="subprocess.Popen.stderr"><code class="xref py py-attr docutils literal notranslate"><span class="pre">Popen.stderr</span></code></a> are not updated by the <a class="reference internal" href="#subprocess.Popen.communicate" title="subprocess.Popen.communicate"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Popen.communicate()</span></code></a> method.</p> </div> <p>If <em>shell</em> is <code class="docutils literal notranslate"><span class="pre">True</span></code>, the specified command will be executed through the shell. This can be useful if you are using Python primarily for the enhanced control flow it offers over most system shells and still want convenient access to other shell features such as shell pipes, filename wildcards, environment variable expansion, and expansion of <code class="docutils literal notranslate"><span class="pre">~</span></code> to a user’s home directory. However, note that Python itself offers implementations of many shell-like features (in particular, <a class="reference internal" href="glob.html#module-glob" title="glob: Unix shell style pathname pattern expansion."><code class="xref py py-mod docutils literal notranslate"><span class="pre">glob</span></code></a>, <a class="reference internal" href="fnmatch.html#module-fnmatch" title="fnmatch: Unix shell style filename pattern matching."><code class="xref py py-mod docutils literal notranslate"><span class="pre">fnmatch</span></code></a>, <a class="reference internal" href="os.html#os.walk" title="os.walk"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.walk()</span></code></a>, <a class="reference internal" href="os.path.html#os.path.expandvars" title="os.path.expandvars"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.path.expandvars()</span></code></a>, <a class="reference internal" href="os.path.html#os.path.expanduser" title="os.path.expanduser"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.path.expanduser()</span></code></a>, and <a class="reference internal" href="shutil.html#module-shutil" title="shutil: High-level file operations, including copying."><code class="xref py py-mod docutils literal notranslate"><span class="pre">shutil</span></code></a>).</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.3: </span>When <em>universal_newlines</em> is <code class="docutils literal notranslate"><span class="pre">True</span></code>, the class uses the encoding <a class="reference internal" href="locale.html#locale.getpreferredencoding" title="locale.getpreferredencoding"><code class="xref py py-func docutils literal notranslate"><span class="pre">locale.getpreferredencoding(False)</span></code></a> instead of <code class="docutils literal notranslate"><span class="pre">locale.getpreferredencoding()</span></code>. See the <a class="reference internal" href="io.html#io.TextIOWrapper" title="io.TextIOWrapper"><code class="xref py py-class docutils literal notranslate"><span class="pre">io.TextIOWrapper</span></code></a> class for more information on this change.</p> </div> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">Read the <a class="reference internal" href="#security-considerations">Security Considerations</a> section before using <code class="docutils literal notranslate"><span class="pre">shell=True</span></code>.</p> </div> </div></blockquote> <p>These options, along with all of the other options, are described in more detail in the <a class="reference internal" href="#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">Popen</span></code></a> constructor documentation.</p> </div> <div class="section" id="popen-constructor"> <h3>17.5.1.2. Popen Constructor<a class="headerlink" href="#popen-constructor" title="Permalink to this headline">¶</a></h3> <p>The underlying process creation and management in this module is handled by the <a class="reference internal" href="#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">Popen</span></code></a> class. It offers a lot of flexibility so that developers are able to handle the less common cases not covered by the convenience functions.</p> <dl class="class"> <dt id="subprocess.Popen"> <em class="property">class </em><code class="descclassname">subprocess.</code><code class="descname">Popen</code><span class="sig-paren">(</span><em>args</em>, <em>bufsize=-1</em>, <em>executable=None</em>, <em>stdin=None</em>, <em>stdout=None</em>, <em>stderr=None</em>, <em>preexec_fn=None</em>, <em>close_fds=True</em>, <em>shell=False</em>, <em>cwd=None</em>, <em>env=None</em>, <em>universal_newlines=False</em>, <em>startupinfo=None</em>, <em>creationflags=0</em>, <em>restore_signals=True</em>, <em>start_new_session=False</em>, <em>pass_fds=()</em>, <em>*</em>, <em>encoding=None</em>, <em>errors=None</em><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.Popen" title="Permalink to this definition">¶</a></dt> <dd><p>Execute a child program in a new process. On POSIX, the class uses <a class="reference internal" href="os.html#os.execvp" title="os.execvp"><code class="xref py py-meth docutils literal notranslate"><span class="pre">os.execvp()</span></code></a>-like behavior to execute the child program. On Windows, the class uses the Windows <code class="docutils literal notranslate"><span class="pre">CreateProcess()</span></code> function. The arguments to <a class="reference internal" href="#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">Popen</span></code></a> are as follows.</p> <p><em>args</em> should be a sequence of program arguments or else a single string. By default, the program to execute is the first item in <em>args</em> if <em>args</em> is a sequence. If <em>args</em> is a string, the interpretation is platform-dependent and described below. See the <em>shell</em> and <em>executable</em> arguments for additional differences from the default behavior. Unless otherwise stated, it is recommended to pass <em>args</em> as a sequence.</p> <p>On POSIX, if <em>args</em> is a string, the string is interpreted as the name or path of the program to execute. However, this can only be done if not passing arguments to the program.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p><a class="reference internal" href="shlex.html#shlex.split" title="shlex.split"><code class="xref py py-meth docutils literal notranslate"><span class="pre">shlex.split()</span></code></a> can be useful when determining the correct tokenization for <em>args</em>, especially in complex cases:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">shlex</span><span class="o">,</span> <span class="nn">subprocess</span> <span class="gp">>>> </span><span class="n">command_line</span> <span class="o">=</span> <span class="nb">input</span><span class="p">()</span> <span class="go">/bin/vikings -input eggs.txt -output "spam spam.txt" -cmd "echo '$MONEY'"</span> <span class="gp">>>> </span><span class="n">args</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">command_line</span><span class="p">)</span> <span class="gp">>>> </span><span class="nb">print</span><span class="p">(</span><span class="n">args</span><span class="p">)</span> <span class="go">['/bin/vikings', '-input', 'eggs.txt', '-output', 'spam spam.txt', '-cmd', "echo '$MONEY'"]</span> <span class="gp">>>> </span><span class="n">p</span> <span class="o">=</span> <span class="n">subprocess</span><span class="o">.</span><span class="n">Popen</span><span class="p">(</span><span class="n">args</span><span class="p">)</span> <span class="c1"># Success!</span> </pre></div> </div> <p class="last">Note in particular that options (such as <em>-input</em>) and arguments (such as <em>eggs.txt</em>) that are separated by whitespace in the shell go in separate list elements, while arguments that need quoting or backslash escaping when used in the shell (such as filenames containing spaces or the <em>echo</em> command shown above) are single list elements.</p> </div> <p>On Windows, if <em>args</em> is a sequence, it will be converted to a string in a manner described in <a class="reference internal" href="#converting-argument-sequence"><span class="std std-ref">Converting an argument sequence to a string on Windows</span></a>. This is because the underlying <code class="docutils literal notranslate"><span class="pre">CreateProcess()</span></code> operates on strings.</p> <p>The <em>shell</em> argument (which defaults to <code class="docutils literal notranslate"><span class="pre">False</span></code>) specifies whether to use the shell as the program to execute. If <em>shell</em> is <code class="docutils literal notranslate"><span class="pre">True</span></code>, it is recommended to pass <em>args</em> as a string rather than as a sequence.</p> <p>On POSIX with <code class="docutils literal notranslate"><span class="pre">shell=True</span></code>, the shell defaults to <code class="file docutils literal notranslate"><span class="pre">/bin/sh</span></code>. If <em>args</em> is a string, the string specifies the command to execute through the shell. This means that the string must be formatted exactly as it would be when typed at the shell prompt. This includes, for example, quoting or backslash escaping filenames with spaces in them. If <em>args</em> is a sequence, the first item specifies the command string, and any additional items will be treated as additional arguments to the shell itself. That is to say, <a class="reference internal" href="#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">Popen</span></code></a> does the equivalent of:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">Popen</span><span class="p">([</span><span class="s1">'/bin/sh'</span><span class="p">,</span> <span class="s1">'-c'</span><span class="p">,</span> <span class="n">args</span><span class="p">[</span><span class="mi">0</span><span class="p">],</span> <span class="n">args</span><span class="p">[</span><span class="mi">1</span><span class="p">],</span> <span class="o">...</span><span class="p">])</span> </pre></div> </div> <p>On Windows with <code class="docutils literal notranslate"><span class="pre">shell=True</span></code>, the <span class="target" id="index-2"></span><code class="xref std std-envvar docutils literal notranslate"><span class="pre">COMSPEC</span></code> environment variable specifies the default shell. The only time you need to specify <code class="docutils literal notranslate"><span class="pre">shell=True</span></code> on Windows is when the command you wish to execute is built into the shell (e.g. <strong class="command">dir</strong> or <strong class="command">copy</strong>). You do not need <code class="docutils literal notranslate"><span class="pre">shell=True</span></code> to run a batch file or console-based executable.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">Read the <a class="reference internal" href="#security-considerations">Security Considerations</a> section before using <code class="docutils literal notranslate"><span class="pre">shell=True</span></code>.</p> </div> <p><em>bufsize</em> will be supplied as the corresponding argument to the <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> function when creating the stdin/stdout/stderr pipe file objects:</p> <ul class="simple"> <li><code class="xref py py-const docutils literal notranslate"><span class="pre">0</span></code> means unbuffered (read and write are one system call and can return short)</li> <li><code class="xref py py-const docutils literal notranslate"><span class="pre">1</span></code> means line buffered (only usable if <code class="docutils literal notranslate"><span class="pre">universal_newlines=True</span></code> i.e., in a text mode)</li> <li>any other positive value means use a buffer of approximately that size</li> <li>negative bufsize (the default) means the system default of io.DEFAULT_BUFFER_SIZE will be used.</li> </ul> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.3.1: </span><em>bufsize</em> now defaults to -1 to enable buffering by default to match the behavior that most code expects. In versions prior to Python 3.2.4 and 3.3.1 it incorrectly defaulted to <code class="xref py py-const docutils literal notranslate"><span class="pre">0</span></code> which was unbuffered and allowed short reads. This was unintentional and did not match the behavior of Python 2 as most code expected.</p> </div> <p>The <em>executable</em> argument specifies a replacement program to execute. It is very seldom needed. When <code class="docutils literal notranslate"><span class="pre">shell=False</span></code>, <em>executable</em> replaces the program to execute specified by <em>args</em>. However, the original <em>args</em> is still passed to the program. Most programs treat the program specified by <em>args</em> as the command name, which can then be different from the program actually executed. On POSIX, the <em>args</em> name becomes the display name for the executable in utilities such as <strong class="program">ps</strong>. If <code class="docutils literal notranslate"><span class="pre">shell=True</span></code>, on POSIX the <em>executable</em> argument specifies a replacement shell for the default <code class="file docutils literal notranslate"><span class="pre">/bin/sh</span></code>.</p> <p><em>stdin</em>, <em>stdout</em> and <em>stderr</em> specify the executed program’s standard input, standard output and standard error file handles, respectively. Valid values are <a class="reference internal" href="#subprocess.PIPE" title="subprocess.PIPE"><code class="xref py py-data docutils literal notranslate"><span class="pre">PIPE</span></code></a>, <a class="reference internal" href="#subprocess.DEVNULL" title="subprocess.DEVNULL"><code class="xref py py-data docutils literal notranslate"><span class="pre">DEVNULL</span></code></a>, an existing file descriptor (a positive integer), an existing <a class="reference internal" href="../glossary.html#term-file-object"><span class="xref std std-term">file object</span></a>, and <code class="docutils literal notranslate"><span class="pre">None</span></code>. <a class="reference internal" href="#subprocess.PIPE" title="subprocess.PIPE"><code class="xref py py-data docutils literal notranslate"><span class="pre">PIPE</span></code></a> indicates that a new pipe to the child should be created. <a class="reference internal" href="#subprocess.DEVNULL" title="subprocess.DEVNULL"><code class="xref py py-data docutils literal notranslate"><span class="pre">DEVNULL</span></code></a> indicates that the special file <a class="reference internal" href="os.html#os.devnull" title="os.devnull"><code class="xref py py-data docutils literal notranslate"><span class="pre">os.devnull</span></code></a> will be used. With the default settings of <code class="docutils literal notranslate"><span class="pre">None</span></code>, no redirection will occur; the child’s file handles will be inherited from the parent. Additionally, <em>stderr</em> can be <a class="reference internal" href="#subprocess.STDOUT" title="subprocess.STDOUT"><code class="xref py py-data docutils literal notranslate"><span class="pre">STDOUT</span></code></a>, which indicates that the stderr data from the applications should be captured into the same file handle as for stdout.</p> <p>If <em>preexec_fn</em> is set to a callable object, this object will be called in the child process just before the child is executed. (POSIX only)</p> <div class="admonition warning"> <p class="first admonition-title">Warning</p> <p class="last">The <em>preexec_fn</em> parameter is not safe to use in the presence of threads in your application. The child process could deadlock before exec is called. If you must use it, keep it trivial! Minimize the number of libraries you call into.</p> </div> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">If you need to modify the environment for the child use the <em>env</em> parameter rather than doing it in a <em>preexec_fn</em>. The <em>start_new_session</em> parameter can take the place of a previously common use of <em>preexec_fn</em> to call os.setsid() in the child.</p> </div> <p>If <em>close_fds</em> is true, all file descriptors except <code class="xref py py-const docutils literal notranslate"><span class="pre">0</span></code>, <code class="xref py py-const docutils literal notranslate"><span class="pre">1</span></code> and <code class="xref py py-const docutils literal notranslate"><span class="pre">2</span></code> will be closed before the child process is executed. (POSIX only). The default varies by platform: Always true on POSIX. On Windows it is true when <em>stdin</em>/<em>stdout</em>/<em>stderr</em> are <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>, false otherwise. On Windows, if <em>close_fds</em> is true then no handles will be inherited by the child process. Note that on Windows, you cannot set <em>close_fds</em> to true and also redirect the standard handles by setting <em>stdin</em>, <em>stdout</em> or <em>stderr</em>.</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.2: </span>The default for <em>close_fds</em> was changed from <a class="reference internal" href="constants.html#False" title="False"><code class="xref py py-const docutils literal notranslate"><span class="pre">False</span></code></a> to what is described above.</p> </div> <p><em>pass_fds</em> is an optional sequence of file descriptors to keep open between the parent and child. Providing any <em>pass_fds</em> forces <em>close_fds</em> to be <a class="reference internal" href="constants.html#True" title="True"><code class="xref py py-const docutils literal notranslate"><span class="pre">True</span></code></a>. (POSIX only)</p> <div class="versionadded"> <p><span class="versionmodified">New in version 3.2: </span>The <em>pass_fds</em> parameter was added.</p> </div> <p>If <em>cwd</em> is not <code class="docutils literal notranslate"><span class="pre">None</span></code>, the function changes the working directory to <em>cwd</em> before executing the child. <em>cwd</em> can be a <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a> and <a class="reference internal" href="../glossary.html#term-path-like-object"><span class="xref std std-term">path-like</span></a> object. In particular, the function looks for <em>executable</em> (or for the first item in <em>args</em>) relative to <em>cwd</em> if the executable path is a relative path.</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.6: </span><em>cwd</em> parameter accepts a <a class="reference internal" href="../glossary.html#term-path-like-object"><span class="xref std std-term">path-like object</span></a>.</p> </div> <p>If <em>restore_signals</em> is true (the default) all signals that Python has set to SIG_IGN are restored to SIG_DFL in the child process before the exec. Currently this includes the SIGPIPE, SIGXFZ and SIGXFSZ signals. (POSIX only)</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.2: </span><em>restore_signals</em> was added.</p> </div> <p>If <em>start_new_session</em> is true the setsid() system call will be made in the child process prior to the execution of the subprocess. (POSIX only)</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.2: </span><em>start_new_session</em> was added.</p> </div> <p>If <em>env</em> is not <code class="docutils literal notranslate"><span class="pre">None</span></code>, it must be a mapping that defines the environment variables for the new process; these are used instead of the default behavior of inheriting the current process’ environment.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">If specified, <em>env</em> must provide any variables required for the program to execute. On Windows, in order to run a <a class="reference external" href="https://en.wikipedia.org/wiki/Side-by-Side_Assembly">side-by-side assembly</a> the specified <em>env</em> <strong>must</strong> include a valid <span class="target" id="index-3"></span><code class="xref std std-envvar docutils literal notranslate"><span class="pre">SystemRoot</span></code>.</p> </div> <p>If <em>encoding</em> or <em>errors</em> are specified, the file objects <em>stdin</em>, <em>stdout</em> and <em>stderr</em> are opened in text mode with the specified encoding and <em>errors</em>, as described above in <a class="reference internal" href="#frequently-used-arguments"><span class="std std-ref">Frequently Used Arguments</span></a>. If <em>universal_newlines</em> is <code class="docutils literal notranslate"><span class="pre">True</span></code>, they are opened in text mode with default encoding. Otherwise, they are opened as binary streams.</p> <div class="versionadded"> <p><span class="versionmodified">New in version 3.6: </span><em>encoding</em> and <em>errors</em> were added.</p> </div> <p>If given, <em>startupinfo</em> will be a <a class="reference internal" href="#subprocess.STARTUPINFO" title="subprocess.STARTUPINFO"><code class="xref py py-class docutils literal notranslate"><span class="pre">STARTUPINFO</span></code></a> object, which is passed to the underlying <code class="docutils literal notranslate"><span class="pre">CreateProcess</span></code> function. <em>creationflags</em>, if given, can be <a class="reference internal" href="#subprocess.CREATE_NEW_CONSOLE" title="subprocess.CREATE_NEW_CONSOLE"><code class="xref py py-data docutils literal notranslate"><span class="pre">CREATE_NEW_CONSOLE</span></code></a> or <a class="reference internal" href="#subprocess.CREATE_NEW_PROCESS_GROUP" title="subprocess.CREATE_NEW_PROCESS_GROUP"><code class="xref py py-data docutils literal notranslate"><span class="pre">CREATE_NEW_PROCESS_GROUP</span></code></a>. (Windows only)</p> <p>Popen objects are supported as context managers via 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: on exit, standard file descriptors are closed, and the process is waited for.</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">with</span> <span class="n">Popen</span><span class="p">([</span><span class="s2">"ifconfig"</span><span class="p">],</span> <span class="n">stdout</span><span class="o">=</span><span class="n">PIPE</span><span class="p">)</span> <span class="k">as</span> <span class="n">proc</span><span class="p">:</span> <span class="n">log</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="n">proc</span><span class="o">.</span><span class="n">stdout</span><span class="o">.</span><span class="n">read</span><span class="p">())</span> </pre></div> </div> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.2: </span>Added context manager support.</p> </div> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.6: </span>Popen destructor now emits a <a class="reference internal" href="exceptions.html#ResourceWarning" title="ResourceWarning"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ResourceWarning</span></code></a> warning if the child process is still running.</p> </div> </dd></dl> </div> <div class="section" id="exceptions"> <h3>17.5.1.3. Exceptions<a class="headerlink" href="#exceptions" title="Permalink to this headline">¶</a></h3> <p>Exceptions raised in the child process, before the new program has started to execute, will be re-raised in the parent. Additionally, the exception object will have one extra attribute called <code class="xref py py-attr docutils literal notranslate"><span class="pre">child_traceback</span></code>, which is a string containing traceback information from the child’s point of view.</p> <p>The most common exception raised is <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>. This occurs, for example, when trying to execute a non-existent file. Applications should prepare for <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> exceptions.</p> <p>A <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ValueError</span></code></a> will be raised if <a class="reference internal" href="#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">Popen</span></code></a> is called with invalid arguments.</p> <p><a class="reference internal" href="#subprocess.check_call" title="subprocess.check_call"><code class="xref py py-func docutils literal notranslate"><span class="pre">check_call()</span></code></a> and <a class="reference internal" href="#subprocess.check_output" title="subprocess.check_output"><code class="xref py py-func docutils literal notranslate"><span class="pre">check_output()</span></code></a> will raise <a class="reference internal" href="#subprocess.CalledProcessError" title="subprocess.CalledProcessError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">CalledProcessError</span></code></a> if the called process returns a non-zero return code.</p> <p>All of the functions and methods that accept a <em>timeout</em> parameter, such as <a class="reference internal" href="#subprocess.call" title="subprocess.call"><code class="xref py py-func docutils literal notranslate"><span class="pre">call()</span></code></a> and <a class="reference internal" href="#subprocess.Popen.communicate" title="subprocess.Popen.communicate"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Popen.communicate()</span></code></a> will raise <a class="reference internal" href="#subprocess.TimeoutExpired" title="subprocess.TimeoutExpired"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TimeoutExpired</span></code></a> if the timeout expires before the process exits.</p> <p>Exceptions defined in this module all inherit from <a class="reference internal" href="#subprocess.SubprocessError" title="subprocess.SubprocessError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">SubprocessError</span></code></a>.</p> <blockquote> <div><div class="versionadded"> <p><span class="versionmodified">New in version 3.3: </span>The <a class="reference internal" href="#subprocess.SubprocessError" title="subprocess.SubprocessError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">SubprocessError</span></code></a> base class was added.</p> </div> </div></blockquote> </div> </div> <div class="section" id="security-considerations"> <h2>17.5.2. Security Considerations<a class="headerlink" href="#security-considerations" title="Permalink to this headline">¶</a></h2> <p>Unlike some other popen functions, this implementation will never implicitly call a system shell. This means that all characters, including shell metacharacters, can safely be passed to child processes. If the shell is invoked explicitly, via <code class="docutils literal notranslate"><span class="pre">shell=True</span></code>, it is the application’s responsibility to ensure that all whitespace and metacharacters are quoted appropriately to avoid <a class="reference external" href="https://en.wikipedia.org/wiki/Shell_injection#Shell_injection">shell injection</a> vulnerabilities.</p> <p>When using <code class="docutils literal notranslate"><span class="pre">shell=True</span></code>, the <a class="reference internal" href="shlex.html#shlex.quote" title="shlex.quote"><code class="xref py py-func docutils literal notranslate"><span class="pre">shlex.quote()</span></code></a> function can be used to properly escape whitespace and shell metacharacters in strings that are going to be used to construct shell commands.</p> </div> <div class="section" id="popen-objects"> <h2>17.5.3. Popen Objects<a class="headerlink" href="#popen-objects" title="Permalink to this headline">¶</a></h2> <p>Instances of the <a class="reference internal" href="#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">Popen</span></code></a> class have the following methods:</p> <dl class="method"> <dt id="subprocess.Popen.poll"> <code class="descclassname">Popen.</code><code class="descname">poll</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.Popen.poll" title="Permalink to this definition">¶</a></dt> <dd><p>Check if child process has terminated. Set and return <a class="reference internal" href="#subprocess.Popen.returncode" title="subprocess.Popen.returncode"><code class="xref py py-attr docutils literal notranslate"><span class="pre">returncode</span></code></a> attribute. Otherwise, returns <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p> </dd></dl> <dl class="method"> <dt id="subprocess.Popen.wait"> <code class="descclassname">Popen.</code><code class="descname">wait</code><span class="sig-paren">(</span><em>timeout=None</em><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.Popen.wait" title="Permalink to this definition">¶</a></dt> <dd><p>Wait for child process to terminate. Set and return <a class="reference internal" href="#subprocess.Popen.returncode" title="subprocess.Popen.returncode"><code class="xref py py-attr docutils literal notranslate"><span class="pre">returncode</span></code></a> attribute.</p> <p>If the process does not terminate after <em>timeout</em> seconds, raise a <a class="reference internal" href="#subprocess.TimeoutExpired" title="subprocess.TimeoutExpired"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TimeoutExpired</span></code></a> exception. It is safe to catch this exception and retry the wait.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">This will deadlock when using <code class="docutils literal notranslate"><span class="pre">stdout=PIPE</span></code> or <code class="docutils literal notranslate"><span class="pre">stderr=PIPE</span></code> and the child process generates enough output to a pipe such that it blocks waiting for the OS pipe buffer to accept more data. Use <a class="reference internal" href="#subprocess.Popen.communicate" title="subprocess.Popen.communicate"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Popen.communicate()</span></code></a> when using pipes to avoid that.</p> </div> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">The function is implemented using a busy loop (non-blocking call and short sleeps). Use the <a class="reference internal" href="asyncio.html#module-asyncio" title="asyncio: Asynchronous I/O, event loop, coroutines and tasks."><code class="xref py py-mod docutils literal notranslate"><span class="pre">asyncio</span></code></a> module for an asynchronous wait: see <a class="reference internal" href="asyncio-subprocess.html#asyncio.create_subprocess_exec" title="asyncio.create_subprocess_exec"><code class="xref py py-class docutils literal notranslate"><span class="pre">asyncio.create_subprocess_exec</span></code></a>.</p> </div> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.3: </span><em>timeout</em> was added.</p> </div> <div class="deprecated"> <p><span class="versionmodified">Deprecated since version 3.4: </span>Do not use the <em>endtime</em> parameter. It is was unintentionally exposed in 3.3 but was left undocumented as it was intended to be private for internal use. Use <em>timeout</em> instead.</p> </div> </dd></dl> <dl class="method"> <dt id="subprocess.Popen.communicate"> <code class="descclassname">Popen.</code><code class="descname">communicate</code><span class="sig-paren">(</span><em>input=None</em>, <em>timeout=None</em><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.Popen.communicate" title="Permalink to this definition">¶</a></dt> <dd><p>Interact with process: Send data to stdin. Read data from stdout and stderr, until end-of-file is reached. Wait for process to terminate. The optional <em>input</em> argument should be data to be sent to the child process, or <code class="docutils literal notranslate"><span class="pre">None</span></code>, if no data should be sent to the child. If streams were opened in text mode, <em>input</em> must be a string. Otherwise, it must be bytes.</p> <p><a class="reference internal" href="#subprocess.Popen.communicate" title="subprocess.Popen.communicate"><code class="xref py py-meth docutils literal notranslate"><span class="pre">communicate()</span></code></a> returns a tuple <code class="docutils literal notranslate"><span class="pre">(stdout_data,</span> <span class="pre">stderr_data)</span></code>. The data will be strings if streams were opened in text mode; otherwise, bytes.</p> <p>Note that if you want to send data to the process’s stdin, you need to create the Popen object with <code class="docutils literal notranslate"><span class="pre">stdin=PIPE</span></code>. Similarly, to get anything other than <code class="docutils literal notranslate"><span class="pre">None</span></code> in the result tuple, you need to give <code class="docutils literal notranslate"><span class="pre">stdout=PIPE</span></code> and/or <code class="docutils literal notranslate"><span class="pre">stderr=PIPE</span></code> too.</p> <p>If the process does not terminate after <em>timeout</em> seconds, a <a class="reference internal" href="#subprocess.TimeoutExpired" title="subprocess.TimeoutExpired"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TimeoutExpired</span></code></a> exception will be raised. Catching this exception and retrying communication will not lose any output.</p> <p>The child process is not killed if the timeout expires, so in order to cleanup properly a well-behaved application should kill the child process and finish communication:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">proc</span> <span class="o">=</span> <span class="n">subprocess</span><span class="o">.</span><span class="n">Popen</span><span class="p">(</span><span class="o">...</span><span class="p">)</span> <span class="k">try</span><span class="p">:</span> <span class="n">outs</span><span class="p">,</span> <span class="n">errs</span> <span class="o">=</span> <span class="n">proc</span><span class="o">.</span><span class="n">communicate</span><span class="p">(</span><span class="n">timeout</span><span class="o">=</span><span class="mi">15</span><span class="p">)</span> <span class="k">except</span> <span class="n">TimeoutExpired</span><span class="p">:</span> <span class="n">proc</span><span class="o">.</span><span class="n">kill</span><span class="p">()</span> <span class="n">outs</span><span class="p">,</span> <span class="n">errs</span> <span class="o">=</span> <span class="n">proc</span><span class="o">.</span><span class="n">communicate</span><span class="p">()</span> </pre></div> </div> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">The data read is buffered in memory, so do not use this method if the data size is large or unlimited.</p> </div> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.3: </span><em>timeout</em> was added.</p> </div> </dd></dl> <dl class="method"> <dt id="subprocess.Popen.send_signal"> <code class="descclassname">Popen.</code><code class="descname">send_signal</code><span class="sig-paren">(</span><em>signal</em><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.Popen.send_signal" title="Permalink to this definition">¶</a></dt> <dd><p>Sends the signal <em>signal</em> to the child.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">On Windows, SIGTERM is an alias for <a class="reference internal" href="#subprocess.Popen.terminate" title="subprocess.Popen.terminate"><code class="xref py py-meth docutils literal notranslate"><span class="pre">terminate()</span></code></a>. CTRL_C_EVENT and CTRL_BREAK_EVENT can be sent to processes started with a <em>creationflags</em> parameter which includes <cite>CREATE_NEW_PROCESS_GROUP</cite>.</p> </div> </dd></dl> <dl class="method"> <dt id="subprocess.Popen.terminate"> <code class="descclassname">Popen.</code><code class="descname">terminate</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.Popen.terminate" title="Permalink to this definition">¶</a></dt> <dd><p>Stop the child. On Posix OSs the method sends SIGTERM to the child. On Windows the Win32 API function <code class="xref c c-func docutils literal notranslate"><span class="pre">TerminateProcess()</span></code> is called to stop the child.</p> </dd></dl> <dl class="method"> <dt id="subprocess.Popen.kill"> <code class="descclassname">Popen.</code><code class="descname">kill</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.Popen.kill" title="Permalink to this definition">¶</a></dt> <dd><p>Kills the child. On Posix OSs the function sends SIGKILL to the child. On Windows <a class="reference internal" href="#subprocess.Popen.kill" title="subprocess.Popen.kill"><code class="xref py py-meth docutils literal notranslate"><span class="pre">kill()</span></code></a> is an alias for <a class="reference internal" href="#subprocess.Popen.terminate" title="subprocess.Popen.terminate"><code class="xref py py-meth docutils literal notranslate"><span class="pre">terminate()</span></code></a>.</p> </dd></dl> <p>The following attributes are also available:</p> <dl class="attribute"> <dt id="subprocess.Popen.args"> <code class="descclassname">Popen.</code><code class="descname">args</code><a class="headerlink" href="#subprocess.Popen.args" title="Permalink to this definition">¶</a></dt> <dd><p>The <em>args</em> argument as it was passed to <a class="reference internal" href="#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">Popen</span></code></a> – a sequence of program arguments or else a single string.</p> <div class="versionadded"> <p><span class="versionmodified">New in version 3.3.</span></p> </div> </dd></dl> <dl class="attribute"> <dt id="subprocess.Popen.stdin"> <code class="descclassname">Popen.</code><code class="descname">stdin</code><a class="headerlink" href="#subprocess.Popen.stdin" title="Permalink to this definition">¶</a></dt> <dd><p>If the <em>stdin</em> argument was <a class="reference internal" href="#subprocess.PIPE" title="subprocess.PIPE"><code class="xref py py-data docutils literal notranslate"><span class="pre">PIPE</span></code></a>, this attribute is a writeable stream object as returned by <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>. If the <em>encoding</em> or <em>errors</em> arguments were specified or the <em>universal_newlines</em> argument was <code class="docutils literal notranslate"><span class="pre">True</span></code>, the stream is a text stream, otherwise it is a byte stream. If the <em>stdin</em> argument was not <a class="reference internal" href="#subprocess.PIPE" title="subprocess.PIPE"><code class="xref py py-data docutils literal notranslate"><span class="pre">PIPE</span></code></a>, this attribute is <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p> </dd></dl> <dl class="attribute"> <dt id="subprocess.Popen.stdout"> <code class="descclassname">Popen.</code><code class="descname">stdout</code><a class="headerlink" href="#subprocess.Popen.stdout" title="Permalink to this definition">¶</a></dt> <dd><p>If the <em>stdout</em> argument was <a class="reference internal" href="#subprocess.PIPE" title="subprocess.PIPE"><code class="xref py py-data docutils literal notranslate"><span class="pre">PIPE</span></code></a>, this attribute is a readable stream object as returned by <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>. Reading from the stream provides output from the child process. If the <em>encoding</em> or <em>errors</em> arguments were specified or the <em>universal_newlines</em> argument was <code class="docutils literal notranslate"><span class="pre">True</span></code>, the stream is a text stream, otherwise it is a byte stream. If the <em>stdout</em> argument was not <a class="reference internal" href="#subprocess.PIPE" title="subprocess.PIPE"><code class="xref py py-data docutils literal notranslate"><span class="pre">PIPE</span></code></a>, this attribute is <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p> </dd></dl> <dl class="attribute"> <dt id="subprocess.Popen.stderr"> <code class="descclassname">Popen.</code><code class="descname">stderr</code><a class="headerlink" href="#subprocess.Popen.stderr" title="Permalink to this definition">¶</a></dt> <dd><p>If the <em>stderr</em> argument was <a class="reference internal" href="#subprocess.PIPE" title="subprocess.PIPE"><code class="xref py py-data docutils literal notranslate"><span class="pre">PIPE</span></code></a>, this attribute is a readable stream object as returned by <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>. Reading from the stream provides error output from the child process. If the <em>encoding</em> or <em>errors</em> arguments were specified or the <em>universal_newlines</em> argument was <code class="docutils literal notranslate"><span class="pre">True</span></code>, the stream is a text stream, otherwise it is a byte stream. If the <em>stderr</em> argument was not <a class="reference internal" href="#subprocess.PIPE" title="subprocess.PIPE"><code class="xref py py-data docutils literal notranslate"><span class="pre">PIPE</span></code></a>, this attribute is <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p> </dd></dl> <div class="admonition warning"> <p class="first admonition-title">Warning</p> <p class="last">Use <a class="reference internal" href="#subprocess.Popen.communicate" title="subprocess.Popen.communicate"><code class="xref py py-meth docutils literal notranslate"><span class="pre">communicate()</span></code></a> rather than <a class="reference internal" href="#subprocess.Popen.stdin" title="subprocess.Popen.stdin"><code class="xref py py-attr docutils literal notranslate"><span class="pre">.stdin.write</span></code></a>, <a class="reference internal" href="#subprocess.Popen.stdout" title="subprocess.Popen.stdout"><code class="xref py py-attr docutils literal notranslate"><span class="pre">.stdout.read</span></code></a> or <a class="reference internal" href="#subprocess.Popen.stderr" title="subprocess.Popen.stderr"><code class="xref py py-attr docutils literal notranslate"><span class="pre">.stderr.read</span></code></a> to avoid deadlocks due to any of the other OS pipe buffers filling up and blocking the child process.</p> </div> <dl class="attribute"> <dt id="subprocess.Popen.pid"> <code class="descclassname">Popen.</code><code class="descname">pid</code><a class="headerlink" href="#subprocess.Popen.pid" title="Permalink to this definition">¶</a></dt> <dd><p>The process ID of the child process.</p> <p>Note that if you set the <em>shell</em> argument to <code class="docutils literal notranslate"><span class="pre">True</span></code>, this is the process ID of the spawned shell.</p> </dd></dl> <dl class="attribute"> <dt id="subprocess.Popen.returncode"> <code class="descclassname">Popen.</code><code class="descname">returncode</code><a class="headerlink" href="#subprocess.Popen.returncode" title="Permalink to this definition">¶</a></dt> <dd><p>The child return code, set by <a class="reference internal" href="#subprocess.Popen.poll" title="subprocess.Popen.poll"><code class="xref py py-meth docutils literal notranslate"><span class="pre">poll()</span></code></a> and <a class="reference internal" href="#subprocess.Popen.wait" title="subprocess.Popen.wait"><code class="xref py py-meth docutils literal notranslate"><span class="pre">wait()</span></code></a> (and indirectly by <a class="reference internal" href="#subprocess.Popen.communicate" title="subprocess.Popen.communicate"><code class="xref py py-meth docutils literal notranslate"><span class="pre">communicate()</span></code></a>). A <code class="docutils literal notranslate"><span class="pre">None</span></code> value indicates that the process hasn’t terminated yet.</p> <p>A negative value <code class="docutils literal notranslate"><span class="pre">-N</span></code> indicates that the child was terminated by signal <code class="docutils literal notranslate"><span class="pre">N</span></code> (POSIX only).</p> </dd></dl> </div> <div class="section" id="windows-popen-helpers"> <h2>17.5.4. Windows Popen Helpers<a class="headerlink" href="#windows-popen-helpers" title="Permalink to this headline">¶</a></h2> <p>The <a class="reference internal" href="#subprocess.STARTUPINFO" title="subprocess.STARTUPINFO"><code class="xref py py-class docutils literal notranslate"><span class="pre">STARTUPINFO</span></code></a> class and following constants are only available on Windows.</p> <dl class="class"> <dt id="subprocess.STARTUPINFO"> <em class="property">class </em><code class="descclassname">subprocess.</code><code class="descname">STARTUPINFO</code><a class="headerlink" href="#subprocess.STARTUPINFO" title="Permalink to this definition">¶</a></dt> <dd><p>Partial support of the Windows <a class="reference external" href="https://msdn.microsoft.com/en-us/library/ms686331(v=vs.85).aspx">STARTUPINFO</a> structure is used for <a class="reference internal" href="#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">Popen</span></code></a> creation.</p> <dl class="attribute"> <dt id="subprocess.STARTUPINFO.dwFlags"> <code class="descname">dwFlags</code><a class="headerlink" href="#subprocess.STARTUPINFO.dwFlags" title="Permalink to this definition">¶</a></dt> <dd><p>A bit field that determines whether certain <a class="reference internal" href="#subprocess.STARTUPINFO" title="subprocess.STARTUPINFO"><code class="xref py py-class docutils literal notranslate"><span class="pre">STARTUPINFO</span></code></a> attributes are used when the process creates a window.</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">si</span> <span class="o">=</span> <span class="n">subprocess</span><span class="o">.</span><span class="n">STARTUPINFO</span><span class="p">()</span> <span class="n">si</span><span class="o">.</span><span class="n">dwFlags</span> <span class="o">=</span> <span class="n">subprocess</span><span class="o">.</span><span class="n">STARTF_USESTDHANDLES</span> <span class="o">|</span> <span class="n">subprocess</span><span class="o">.</span><span class="n">STARTF_USESHOWWINDOW</span> </pre></div> </div> </dd></dl> <dl class="attribute"> <dt id="subprocess.STARTUPINFO.hStdInput"> <code class="descname">hStdInput</code><a class="headerlink" href="#subprocess.STARTUPINFO.hStdInput" title="Permalink to this definition">¶</a></dt> <dd><p>If <a class="reference internal" href="#subprocess.STARTUPINFO.dwFlags" title="subprocess.STARTUPINFO.dwFlags"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dwFlags</span></code></a> specifies <a class="reference internal" href="#subprocess.STARTF_USESTDHANDLES" title="subprocess.STARTF_USESTDHANDLES"><code class="xref py py-data docutils literal notranslate"><span class="pre">STARTF_USESTDHANDLES</span></code></a>, this attribute is the standard input handle for the process. If <a class="reference internal" href="#subprocess.STARTF_USESTDHANDLES" title="subprocess.STARTF_USESTDHANDLES"><code class="xref py py-data docutils literal notranslate"><span class="pre">STARTF_USESTDHANDLES</span></code></a> is not specified, the default for standard input is the keyboard buffer.</p> </dd></dl> <dl class="attribute"> <dt id="subprocess.STARTUPINFO.hStdOutput"> <code class="descname">hStdOutput</code><a class="headerlink" href="#subprocess.STARTUPINFO.hStdOutput" title="Permalink to this definition">¶</a></dt> <dd><p>If <a class="reference internal" href="#subprocess.STARTUPINFO.dwFlags" title="subprocess.STARTUPINFO.dwFlags"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dwFlags</span></code></a> specifies <a class="reference internal" href="#subprocess.STARTF_USESTDHANDLES" title="subprocess.STARTF_USESTDHANDLES"><code class="xref py py-data docutils literal notranslate"><span class="pre">STARTF_USESTDHANDLES</span></code></a>, this attribute is the standard output handle for the process. Otherwise, this attribute is ignored and the default for standard output is the console window’s buffer.</p> </dd></dl> <dl class="attribute"> <dt id="subprocess.STARTUPINFO.hStdError"> <code class="descname">hStdError</code><a class="headerlink" href="#subprocess.STARTUPINFO.hStdError" title="Permalink to this definition">¶</a></dt> <dd><p>If <a class="reference internal" href="#subprocess.STARTUPINFO.dwFlags" title="subprocess.STARTUPINFO.dwFlags"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dwFlags</span></code></a> specifies <a class="reference internal" href="#subprocess.STARTF_USESTDHANDLES" title="subprocess.STARTF_USESTDHANDLES"><code class="xref py py-data docutils literal notranslate"><span class="pre">STARTF_USESTDHANDLES</span></code></a>, this attribute is the standard error handle for the process. Otherwise, this attribute is ignored and the default for standard error is the console window’s buffer.</p> </dd></dl> <dl class="attribute"> <dt id="subprocess.STARTUPINFO.wShowWindow"> <code class="descname">wShowWindow</code><a class="headerlink" href="#subprocess.STARTUPINFO.wShowWindow" title="Permalink to this definition">¶</a></dt> <dd><p>If <a class="reference internal" href="#subprocess.STARTUPINFO.dwFlags" title="subprocess.STARTUPINFO.dwFlags"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dwFlags</span></code></a> specifies <a class="reference internal" href="#subprocess.STARTF_USESHOWWINDOW" title="subprocess.STARTF_USESHOWWINDOW"><code class="xref py py-data docutils literal notranslate"><span class="pre">STARTF_USESHOWWINDOW</span></code></a>, this attribute can be any of the values that can be specified in the <code class="docutils literal notranslate"><span class="pre">nCmdShow</span></code> parameter for the <a class="reference external" href="https://msdn.microsoft.com/en-us/library/ms633548(v=vs.85).aspx">ShowWindow</a> function, except for <code class="docutils literal notranslate"><span class="pre">SW_SHOWDEFAULT</span></code>. Otherwise, this attribute is ignored.</p> <p><a class="reference internal" href="#subprocess.SW_HIDE" title="subprocess.SW_HIDE"><code class="xref py py-data docutils literal notranslate"><span class="pre">SW_HIDE</span></code></a> is provided for this attribute. It is used when <a class="reference internal" href="#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">Popen</span></code></a> is called with <code class="docutils literal notranslate"><span class="pre">shell=True</span></code>.</p> </dd></dl> </dd></dl> <div class="section" id="constants"> <h3>17.5.4.1. Constants<a class="headerlink" href="#constants" title="Permalink to this headline">¶</a></h3> <p>The <a class="reference internal" href="#module-subprocess" title="subprocess: Subprocess management."><code class="xref py py-mod docutils literal notranslate"><span class="pre">subprocess</span></code></a> module exposes the following constants.</p> <dl class="data"> <dt id="subprocess.STD_INPUT_HANDLE"> <code class="descclassname">subprocess.</code><code class="descname">STD_INPUT_HANDLE</code><a class="headerlink" href="#subprocess.STD_INPUT_HANDLE" title="Permalink to this definition">¶</a></dt> <dd><p>The standard input device. Initially, this is the console input buffer, <code class="docutils literal notranslate"><span class="pre">CONIN$</span></code>.</p> </dd></dl> <dl class="data"> <dt id="subprocess.STD_OUTPUT_HANDLE"> <code class="descclassname">subprocess.</code><code class="descname">STD_OUTPUT_HANDLE</code><a class="headerlink" href="#subprocess.STD_OUTPUT_HANDLE" title="Permalink to this definition">¶</a></dt> <dd><p>The standard output device. Initially, this is the active console screen buffer, <code class="docutils literal notranslate"><span class="pre">CONOUT$</span></code>.</p> </dd></dl> <dl class="data"> <dt id="subprocess.STD_ERROR_HANDLE"> <code class="descclassname">subprocess.</code><code class="descname">STD_ERROR_HANDLE</code><a class="headerlink" href="#subprocess.STD_ERROR_HANDLE" title="Permalink to this definition">¶</a></dt> <dd><p>The standard error device. Initially, this is the active console screen buffer, <code class="docutils literal notranslate"><span class="pre">CONOUT$</span></code>.</p> </dd></dl> <dl class="data"> <dt id="subprocess.SW_HIDE"> <code class="descclassname">subprocess.</code><code class="descname">SW_HIDE</code><a class="headerlink" href="#subprocess.SW_HIDE" title="Permalink to this definition">¶</a></dt> <dd><p>Hides the window. Another window will be activated.</p> </dd></dl> <dl class="data"> <dt id="subprocess.STARTF_USESTDHANDLES"> <code class="descclassname">subprocess.</code><code class="descname">STARTF_USESTDHANDLES</code><a class="headerlink" href="#subprocess.STARTF_USESTDHANDLES" title="Permalink to this definition">¶</a></dt> <dd><p>Specifies that the <a class="reference internal" href="#subprocess.STARTUPINFO.hStdInput" title="subprocess.STARTUPINFO.hStdInput"><code class="xref py py-attr docutils literal notranslate"><span class="pre">STARTUPINFO.hStdInput</span></code></a>, <a class="reference internal" href="#subprocess.STARTUPINFO.hStdOutput" title="subprocess.STARTUPINFO.hStdOutput"><code class="xref py py-attr docutils literal notranslate"><span class="pre">STARTUPINFO.hStdOutput</span></code></a>, and <a class="reference internal" href="#subprocess.STARTUPINFO.hStdError" title="subprocess.STARTUPINFO.hStdError"><code class="xref py py-attr docutils literal notranslate"><span class="pre">STARTUPINFO.hStdError</span></code></a> attributes contain additional information.</p> </dd></dl> <dl class="data"> <dt id="subprocess.STARTF_USESHOWWINDOW"> <code class="descclassname">subprocess.</code><code class="descname">STARTF_USESHOWWINDOW</code><a class="headerlink" href="#subprocess.STARTF_USESHOWWINDOW" title="Permalink to this definition">¶</a></dt> <dd><p>Specifies that the <a class="reference internal" href="#subprocess.STARTUPINFO.wShowWindow" title="subprocess.STARTUPINFO.wShowWindow"><code class="xref py py-attr docutils literal notranslate"><span class="pre">STARTUPINFO.wShowWindow</span></code></a> attribute contains additional information.</p> </dd></dl> <dl class="data"> <dt id="subprocess.CREATE_NEW_CONSOLE"> <code class="descclassname">subprocess.</code><code class="descname">CREATE_NEW_CONSOLE</code><a class="headerlink" href="#subprocess.CREATE_NEW_CONSOLE" title="Permalink to this definition">¶</a></dt> <dd><p>The new process has a new console, instead of inheriting its parent’s console (the default).</p> </dd></dl> <dl class="data"> <dt id="subprocess.CREATE_NEW_PROCESS_GROUP"> <code class="descclassname">subprocess.</code><code class="descname">CREATE_NEW_PROCESS_GROUP</code><a class="headerlink" href="#subprocess.CREATE_NEW_PROCESS_GROUP" title="Permalink to this definition">¶</a></dt> <dd><p>A <a class="reference internal" href="#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">Popen</span></code></a> <code class="docutils literal notranslate"><span class="pre">creationflags</span></code> parameter to specify that a new process group will be created. This flag is necessary for using <a class="reference internal" href="os.html#os.kill" title="os.kill"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.kill()</span></code></a> on the subprocess.</p> <p>This flag is ignored if <a class="reference internal" href="#subprocess.CREATE_NEW_CONSOLE" title="subprocess.CREATE_NEW_CONSOLE"><code class="xref py py-data docutils literal notranslate"><span class="pre">CREATE_NEW_CONSOLE</span></code></a> is specified.</p> </dd></dl> </div> </div> <div class="section" id="older-high-level-api"> <span id="call-function-trio"></span><h2>17.5.5. Older high-level API<a class="headerlink" href="#older-high-level-api" title="Permalink to this headline">¶</a></h2> <p>Prior to Python 3.5, these three functions comprised the high level API to subprocess. You can now use <a class="reference internal" href="#subprocess.run" title="subprocess.run"><code class="xref py py-func docutils literal notranslate"><span class="pre">run()</span></code></a> in many cases, but lots of existing code calls these functions.</p> <dl class="function"> <dt id="subprocess.call"> <code class="descclassname">subprocess.</code><code class="descname">call</code><span class="sig-paren">(</span><em>args</em>, <em>*</em>, <em>stdin=None</em>, <em>stdout=None</em>, <em>stderr=None</em>, <em>shell=False</em>, <em>cwd=None</em>, <em>timeout=None</em><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.call" title="Permalink to this definition">¶</a></dt> <dd><p>Run the command described by <em>args</em>. Wait for command to complete, then return the <a class="reference internal" href="#subprocess.Popen.returncode" title="subprocess.Popen.returncode"><code class="xref py py-attr docutils literal notranslate"><span class="pre">returncode</span></code></a> attribute.</p> <p>This is equivalent to:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">run</span><span class="p">(</span><span class="o">...</span><span class="p">)</span><span class="o">.</span><span class="n">returncode</span> </pre></div> </div> <p>(except that the <em>input</em> and <em>check</em> parameters are not supported)</p> <p>The arguments shown above are merely the most common ones. The full function signature is largely the same as that of the <a class="reference internal" href="#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">Popen</span></code></a> constructor - this function passes all supplied arguments other than <em>timeout</em> directly through to that interface.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">Do not use <code class="docutils literal notranslate"><span class="pre">stdout=PIPE</span></code> or <code class="docutils literal notranslate"><span class="pre">stderr=PIPE</span></code> with this function. The child process will block if it generates enough output to a pipe to fill up the OS pipe buffer as the pipes are not being read from.</p> </div> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.3: </span><em>timeout</em> was added.</p> </div> </dd></dl> <dl class="function"> <dt id="subprocess.check_call"> <code class="descclassname">subprocess.</code><code class="descname">check_call</code><span class="sig-paren">(</span><em>args</em>, <em>*</em>, <em>stdin=None</em>, <em>stdout=None</em>, <em>stderr=None</em>, <em>shell=False</em>, <em>cwd=None</em>, <em>timeout=None</em><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.check_call" title="Permalink to this definition">¶</a></dt> <dd><p>Run command with arguments. Wait for command to complete. If the return code was zero then return, otherwise raise <a class="reference internal" href="#subprocess.CalledProcessError" title="subprocess.CalledProcessError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">CalledProcessError</span></code></a>. The <a class="reference internal" href="#subprocess.CalledProcessError" title="subprocess.CalledProcessError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">CalledProcessError</span></code></a> object will have the return code in the <a class="reference internal" href="#subprocess.CalledProcessError.returncode" title="subprocess.CalledProcessError.returncode"><code class="xref py py-attr docutils literal notranslate"><span class="pre">returncode</span></code></a> attribute.</p> <p>This is equivalent to:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">run</span><span class="p">(</span><span class="o">...</span><span class="p">,</span> <span class="n">check</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span> </pre></div> </div> <p>(except that the <em>input</em> parameter is not supported)</p> <p>The arguments shown above are merely the most common ones. The full function signature is largely the same as that of the <a class="reference internal" href="#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">Popen</span></code></a> constructor - this function passes all supplied arguments other than <em>timeout</em> directly through to that interface.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">Do not use <code class="docutils literal notranslate"><span class="pre">stdout=PIPE</span></code> or <code class="docutils literal notranslate"><span class="pre">stderr=PIPE</span></code> with this function. The child process will block if it generates enough output to a pipe to fill up the OS pipe buffer as the pipes are not being read from.</p> </div> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.3: </span><em>timeout</em> was added.</p> </div> </dd></dl> <dl class="function"> <dt id="subprocess.check_output"> <code class="descclassname">subprocess.</code><code class="descname">check_output</code><span class="sig-paren">(</span><em>args</em>, <em>*</em>, <em>stdin=None</em>, <em>stderr=None</em>, <em>shell=False</em>, <em>cwd=None</em>, <em>encoding=None</em>, <em>errors=None</em>, <em>universal_newlines=False</em>, <em>timeout=None</em><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.check_output" title="Permalink to this definition">¶</a></dt> <dd><p>Run command with arguments and return its output.</p> <p>If the return code was non-zero it raises a <a class="reference internal" href="#subprocess.CalledProcessError" title="subprocess.CalledProcessError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">CalledProcessError</span></code></a>. The <a class="reference internal" href="#subprocess.CalledProcessError" title="subprocess.CalledProcessError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">CalledProcessError</span></code></a> object will have the return code in the <a class="reference internal" href="#subprocess.CalledProcessError.returncode" title="subprocess.CalledProcessError.returncode"><code class="xref py py-attr docutils literal notranslate"><span class="pre">returncode</span></code></a> attribute and any output in the <a class="reference internal" href="#subprocess.CalledProcessError.output" title="subprocess.CalledProcessError.output"><code class="xref py py-attr docutils literal notranslate"><span class="pre">output</span></code></a> attribute.</p> <p>This is equivalent to:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">run</span><span class="p">(</span><span class="o">...</span><span class="p">,</span> <span class="n">check</span><span class="o">=</span><span class="kc">True</span><span class="p">,</span> <span class="n">stdout</span><span class="o">=</span><span class="n">PIPE</span><span class="p">)</span><span class="o">.</span><span class="n">stdout</span> </pre></div> </div> <p>The arguments shown above are merely the most common ones. The full function signature is largely the same as that of <a class="reference internal" href="#subprocess.run" title="subprocess.run"><code class="xref py py-func docutils literal notranslate"><span class="pre">run()</span></code></a> - most arguments are passed directly through to that interface. However, explicitly passing <code class="docutils literal notranslate"><span class="pre">input=None</span></code> to inherit the parent’s standard input file handle is not supported.</p> <p>By default, this function will return the data as encoded bytes. The actual encoding of the output data may depend on the command being invoked, so the decoding to text will often need to be handled at the application level.</p> <p>This behaviour may be overridden by setting <em>universal_newlines</em> to <code class="docutils literal notranslate"><span class="pre">True</span></code> as described above in <a class="reference internal" href="#frequently-used-arguments"><span class="std std-ref">Frequently Used Arguments</span></a>.</p> <p>To also capture standard error in the result, use <code class="docutils literal notranslate"><span class="pre">stderr=subprocess.STDOUT</span></code>:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">subprocess</span><span class="o">.</span><span class="n">check_output</span><span class="p">(</span> <span class="gp">... </span> <span class="s2">"ls non_existent_file; exit 0"</span><span class="p">,</span> <span class="gp">... </span> <span class="n">stderr</span><span class="o">=</span><span class="n">subprocess</span><span class="o">.</span><span class="n">STDOUT</span><span class="p">,</span> <span class="gp">... </span> <span class="n">shell</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span> <span class="go">'ls: non_existent_file: No such file or directory\n'</span> </pre></div> </div> <div class="versionadded"> <p><span class="versionmodified">New in version 3.1.</span></p> </div> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.3: </span><em>timeout</em> was added.</p> </div> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.4: </span>Support for the <em>input</em> keyword argument was added.</p> </div> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.6: </span><em>encoding</em> and <em>errors</em> were added. See <a class="reference internal" href="#subprocess.run" title="subprocess.run"><code class="xref py py-func docutils literal notranslate"><span class="pre">run()</span></code></a> for details.</p> </div> </dd></dl> </div> <div class="section" id="replacing-older-functions-with-the-subprocess-module"> <span id="subprocess-replacements"></span><h2>17.5.6. Replacing Older Functions with the <a class="reference internal" href="#module-subprocess" title="subprocess: Subprocess management."><code class="xref py py-mod docutils literal notranslate"><span class="pre">subprocess</span></code></a> Module<a class="headerlink" href="#replacing-older-functions-with-the-subprocess-module" title="Permalink to this headline">¶</a></h2> <p>In this section, “a becomes b” means that b can be used as a replacement for a.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p>All “a” functions in this section fail (more or less) silently if the executed program cannot be found; the “b” replacements raise <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> instead.</p> <p class="last">In addition, the replacements using <a class="reference internal" href="#subprocess.check_output" title="subprocess.check_output"><code class="xref py py-func docutils literal notranslate"><span class="pre">check_output()</span></code></a> will fail with a <a class="reference internal" href="#subprocess.CalledProcessError" title="subprocess.CalledProcessError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">CalledProcessError</span></code></a> if the requested operation produces a non-zero return code. The output is still available as the <a class="reference internal" href="#subprocess.CalledProcessError.output" title="subprocess.CalledProcessError.output"><code class="xref py py-attr docutils literal notranslate"><span class="pre">output</span></code></a> attribute of the raised exception.</p> </div> <p>In the following examples, we assume that the relevant functions have already been imported from the <a class="reference internal" href="#module-subprocess" title="subprocess: Subprocess management."><code class="xref py py-mod docutils literal notranslate"><span class="pre">subprocess</span></code></a> module.</p> <div class="section" id="replacing-bin-sh-shell-backquote"> <h3>17.5.6.1. Replacing /bin/sh shell backquote<a class="headerlink" href="#replacing-bin-sh-shell-backquote" title="Permalink to this headline">¶</a></h3> <div class="highlight-bash notranslate"><div class="highlight"><pre><span></span><span class="nv">output</span><span class="o">=</span><span class="sb">`</span>mycmd myarg<span class="sb">`</span> </pre></div> </div> <p>becomes:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">output</span> <span class="o">=</span> <span class="n">check_output</span><span class="p">([</span><span class="s2">"mycmd"</span><span class="p">,</span> <span class="s2">"myarg"</span><span class="p">])</span> </pre></div> </div> </div> <div class="section" id="replacing-shell-pipeline"> <h3>17.5.6.2. Replacing shell pipeline<a class="headerlink" href="#replacing-shell-pipeline" title="Permalink to this headline">¶</a></h3> <div class="highlight-bash notranslate"><div class="highlight"><pre><span></span><span class="nv">output</span><span class="o">=</span><span class="sb">`</span>dmesg <span class="p">|</span> grep hda<span class="sb">`</span> </pre></div> </div> <p>becomes:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">p1</span> <span class="o">=</span> <span class="n">Popen</span><span class="p">([</span><span class="s2">"dmesg"</span><span class="p">],</span> <span class="n">stdout</span><span class="o">=</span><span class="n">PIPE</span><span class="p">)</span> <span class="n">p2</span> <span class="o">=</span> <span class="n">Popen</span><span class="p">([</span><span class="s2">"grep"</span><span class="p">,</span> <span class="s2">"hda"</span><span class="p">],</span> <span class="n">stdin</span><span class="o">=</span><span class="n">p1</span><span class="o">.</span><span class="n">stdout</span><span class="p">,</span> <span class="n">stdout</span><span class="o">=</span><span class="n">PIPE</span><span class="p">)</span> <span class="n">p1</span><span class="o">.</span><span class="n">stdout</span><span class="o">.</span><span class="n">close</span><span class="p">()</span> <span class="c1"># Allow p1 to receive a SIGPIPE if p2 exits.</span> <span class="n">output</span> <span class="o">=</span> <span class="n">p2</span><span class="o">.</span><span class="n">communicate</span><span class="p">()[</span><span class="mi">0</span><span class="p">]</span> </pre></div> </div> <p>The p1.stdout.close() call after starting the p2 is important in order for p1 to receive a SIGPIPE if p2 exits before p1.</p> <p>Alternatively, for trusted input, the shell’s own pipeline support may still be used directly:</p> <div class="highlight-bash notranslate"><div class="highlight"><pre><span></span><span class="nv">output</span><span class="o">=</span><span class="sb">`</span>dmesg <span class="p">|</span> grep hda<span class="sb">`</span> </pre></div> </div> <p>becomes:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">output</span><span class="o">=</span><span class="n">check_output</span><span class="p">(</span><span class="s2">"dmesg | grep hda"</span><span class="p">,</span> <span class="n">shell</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span> </pre></div> </div> </div> <div class="section" id="replacing-os-system"> <h3>17.5.6.3. Replacing <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><a class="headerlink" href="#replacing-os-system" title="Permalink to this headline">¶</a></h3> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">sts</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">system</span><span class="p">(</span><span class="s2">"mycmd"</span> <span class="o">+</span> <span class="s2">" myarg"</span><span class="p">)</span> <span class="c1"># becomes</span> <span class="n">sts</span> <span class="o">=</span> <span class="n">call</span><span class="p">(</span><span class="s2">"mycmd"</span> <span class="o">+</span> <span class="s2">" myarg"</span><span class="p">,</span> <span class="n">shell</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span> </pre></div> </div> <p>Notes:</p> <ul class="simple"> <li>Calling the program through the shell is usually not required.</li> </ul> <p>A more realistic example would look like this:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">try</span><span class="p">:</span> <span class="n">retcode</span> <span class="o">=</span> <span class="n">call</span><span class="p">(</span><span class="s2">"mycmd"</span> <span class="o">+</span> <span class="s2">" myarg"</span><span class="p">,</span> <span class="n">shell</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span> <span class="k">if</span> <span class="n">retcode</span> <span class="o"><</span> <span class="mi">0</span><span class="p">:</span> <span class="nb">print</span><span class="p">(</span><span class="s2">"Child was terminated by signal"</span><span class="p">,</span> <span class="o">-</span><span class="n">retcode</span><span class="p">,</span> <span class="n">file</span><span class="o">=</span><span class="n">sys</span><span class="o">.</span><span class="n">stderr</span><span class="p">)</span> <span class="k">else</span><span class="p">:</span> <span class="nb">print</span><span class="p">(</span><span class="s2">"Child returned"</span><span class="p">,</span> <span class="n">retcode</span><span class="p">,</span> <span class="n">file</span><span class="o">=</span><span class="n">sys</span><span class="o">.</span><span class="n">stderr</span><span class="p">)</span> <span class="k">except</span> <span class="ne">OSError</span> <span class="k">as</span> <span class="n">e</span><span class="p">:</span> <span class="nb">print</span><span class="p">(</span><span class="s2">"Execution failed:"</span><span class="p">,</span> <span class="n">e</span><span class="p">,</span> <span class="n">file</span><span class="o">=</span><span class="n">sys</span><span class="o">.</span><span class="n">stderr</span><span class="p">)</span> </pre></div> </div> </div> <div class="section" id="replacing-the-os-spawn-family"> <h3>17.5.6.4. Replacing the <a class="reference internal" href="os.html#os.spawnl" title="os.spawnl"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.spawn</span></code></a> family<a class="headerlink" href="#replacing-the-os-spawn-family" title="Permalink to this headline">¶</a></h3> <p>P_NOWAIT example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">pid</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">spawnlp</span><span class="p">(</span><span class="n">os</span><span class="o">.</span><span class="n">P_NOWAIT</span><span class="p">,</span> <span class="s2">"/bin/mycmd"</span><span class="p">,</span> <span class="s2">"mycmd"</span><span class="p">,</span> <span class="s2">"myarg"</span><span class="p">)</span> <span class="o">==></span> <span class="n">pid</span> <span class="o">=</span> <span class="n">Popen</span><span class="p">([</span><span class="s2">"/bin/mycmd"</span><span class="p">,</span> <span class="s2">"myarg"</span><span class="p">])</span><span class="o">.</span><span class="n">pid</span> </pre></div> </div> <p>P_WAIT example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">retcode</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">spawnlp</span><span class="p">(</span><span class="n">os</span><span class="o">.</span><span class="n">P_WAIT</span><span class="p">,</span> <span class="s2">"/bin/mycmd"</span><span class="p">,</span> <span class="s2">"mycmd"</span><span class="p">,</span> <span class="s2">"myarg"</span><span class="p">)</span> <span class="o">==></span> <span class="n">retcode</span> <span class="o">=</span> <span class="n">call</span><span class="p">([</span><span class="s2">"/bin/mycmd"</span><span class="p">,</span> <span class="s2">"myarg"</span><span class="p">])</span> </pre></div> </div> <p>Vector example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">os</span><span class="o">.</span><span class="n">spawnvp</span><span class="p">(</span><span class="n">os</span><span class="o">.</span><span class="n">P_NOWAIT</span><span class="p">,</span> <span class="n">path</span><span class="p">,</span> <span class="n">args</span><span class="p">)</span> <span class="o">==></span> <span class="n">Popen</span><span class="p">([</span><span class="n">path</span><span class="p">]</span> <span class="o">+</span> <span class="n">args</span><span class="p">[</span><span class="mi">1</span><span class="p">:])</span> </pre></div> </div> <p>Environment example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">os</span><span class="o">.</span><span class="n">spawnlpe</span><span class="p">(</span><span class="n">os</span><span class="o">.</span><span class="n">P_NOWAIT</span><span class="p">,</span> <span class="s2">"/bin/mycmd"</span><span class="p">,</span> <span class="s2">"mycmd"</span><span class="p">,</span> <span class="s2">"myarg"</span><span class="p">,</span> <span class="n">env</span><span class="p">)</span> <span class="o">==></span> <span class="n">Popen</span><span class="p">([</span><span class="s2">"/bin/mycmd"</span><span class="p">,</span> <span class="s2">"myarg"</span><span class="p">],</span> <span class="n">env</span><span class="o">=</span><span class="p">{</span><span class="s2">"PATH"</span><span class="p">:</span> <span class="s2">"/usr/bin"</span><span class="p">})</span> </pre></div> </div> </div> <div class="section" id="replacing-os-popen-os-popen2-os-popen3"> <h3>17.5.6.5. Replacing <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>, <code class="xref py py-func docutils literal notranslate"><span class="pre">os.popen2()</span></code>, <code class="xref py py-func docutils literal notranslate"><span class="pre">os.popen3()</span></code><a class="headerlink" href="#replacing-os-popen-os-popen2-os-popen3" title="Permalink to this headline">¶</a></h3> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="p">(</span><span class="n">child_stdin</span><span class="p">,</span> <span class="n">child_stdout</span><span class="p">)</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">popen2</span><span class="p">(</span><span class="n">cmd</span><span class="p">,</span> <span class="n">mode</span><span class="p">,</span> <span class="n">bufsize</span><span class="p">)</span> <span class="o">==></span> <span class="n">p</span> <span class="o">=</span> <span class="n">Popen</span><span class="p">(</span><span class="n">cmd</span><span class="p">,</span> <span class="n">shell</span><span class="o">=</span><span class="kc">True</span><span class="p">,</span> <span class="n">bufsize</span><span class="o">=</span><span class="n">bufsize</span><span class="p">,</span> <span class="n">stdin</span><span class="o">=</span><span class="n">PIPE</span><span class="p">,</span> <span class="n">stdout</span><span class="o">=</span><span class="n">PIPE</span><span class="p">,</span> <span class="n">close_fds</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span> <span class="p">(</span><span class="n">child_stdin</span><span class="p">,</span> <span class="n">child_stdout</span><span class="p">)</span> <span class="o">=</span> <span class="p">(</span><span class="n">p</span><span class="o">.</span><span class="n">stdin</span><span class="p">,</span> <span class="n">p</span><span class="o">.</span><span class="n">stdout</span><span class="p">)</span> </pre></div> </div> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="p">(</span><span class="n">child_stdin</span><span class="p">,</span> <span class="n">child_stdout</span><span class="p">,</span> <span class="n">child_stderr</span><span class="p">)</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">popen3</span><span class="p">(</span><span class="n">cmd</span><span class="p">,</span> <span class="n">mode</span><span class="p">,</span> <span class="n">bufsize</span><span class="p">)</span> <span class="o">==></span> <span class="n">p</span> <span class="o">=</span> <span class="n">Popen</span><span class="p">(</span><span class="n">cmd</span><span class="p">,</span> <span class="n">shell</span><span class="o">=</span><span class="kc">True</span><span class="p">,</span> <span class="n">bufsize</span><span class="o">=</span><span class="n">bufsize</span><span class="p">,</span> <span class="n">stdin</span><span class="o">=</span><span class="n">PIPE</span><span class="p">,</span> <span class="n">stdout</span><span class="o">=</span><span class="n">PIPE</span><span class="p">,</span> <span class="n">stderr</span><span class="o">=</span><span class="n">PIPE</span><span class="p">,</span> <span class="n">close_fds</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span> <span class="p">(</span><span class="n">child_stdin</span><span class="p">,</span> <span class="n">child_stdout</span><span class="p">,</span> <span class="n">child_stderr</span><span class="p">)</span> <span class="o">=</span> <span class="p">(</span><span class="n">p</span><span class="o">.</span><span class="n">stdin</span><span class="p">,</span> <span class="n">p</span><span class="o">.</span><span class="n">stdout</span><span class="p">,</span> <span class="n">p</span><span class="o">.</span><span class="n">stderr</span><span class="p">)</span> </pre></div> </div> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="p">(</span><span class="n">child_stdin</span><span class="p">,</span> <span class="n">child_stdout_and_stderr</span><span class="p">)</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">popen4</span><span class="p">(</span><span class="n">cmd</span><span class="p">,</span> <span class="n">mode</span><span class="p">,</span> <span class="n">bufsize</span><span class="p">)</span> <span class="o">==></span> <span class="n">p</span> <span class="o">=</span> <span class="n">Popen</span><span class="p">(</span><span class="n">cmd</span><span class="p">,</span> <span class="n">shell</span><span class="o">=</span><span class="kc">True</span><span class="p">,</span> <span class="n">bufsize</span><span class="o">=</span><span class="n">bufsize</span><span class="p">,</span> <span class="n">stdin</span><span class="o">=</span><span class="n">PIPE</span><span class="p">,</span> <span class="n">stdout</span><span class="o">=</span><span class="n">PIPE</span><span class="p">,</span> <span class="n">stderr</span><span class="o">=</span><span class="n">STDOUT</span><span class="p">,</span> <span class="n">close_fds</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span> <span class="p">(</span><span class="n">child_stdin</span><span class="p">,</span> <span class="n">child_stdout_and_stderr</span><span class="p">)</span> <span class="o">=</span> <span class="p">(</span><span class="n">p</span><span class="o">.</span><span class="n">stdin</span><span class="p">,</span> <span class="n">p</span><span class="o">.</span><span class="n">stdout</span><span class="p">)</span> </pre></div> </div> <p>Return code handling translates as follows:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">pipe</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">popen</span><span class="p">(</span><span class="n">cmd</span><span class="p">,</span> <span class="s1">'w'</span><span class="p">)</span> <span class="o">...</span> <span class="n">rc</span> <span class="o">=</span> <span class="n">pipe</span><span class="o">.</span><span class="n">close</span><span class="p">()</span> <span class="k">if</span> <span class="n">rc</span> <span class="ow">is</span> <span class="ow">not</span> <span class="kc">None</span> <span class="ow">and</span> <span class="n">rc</span> <span class="o">>></span> <span class="mi">8</span><span class="p">:</span> <span class="nb">print</span><span class="p">(</span><span class="s2">"There were some errors"</span><span class="p">)</span> <span class="o">==></span> <span class="n">process</span> <span class="o">=</span> <span class="n">Popen</span><span class="p">(</span><span class="n">cmd</span><span class="p">,</span> <span class="n">stdin</span><span class="o">=</span><span class="n">PIPE</span><span class="p">)</span> <span class="o">...</span> <span class="n">process</span><span class="o">.</span><span class="n">stdin</span><span class="o">.</span><span class="n">close</span><span class="p">()</span> <span class="k">if</span> <span class="n">process</span><span class="o">.</span><span class="n">wait</span><span class="p">()</span> <span class="o">!=</span> <span class="mi">0</span><span class="p">:</span> <span class="nb">print</span><span class="p">(</span><span class="s2">"There were some errors"</span><span class="p">)</span> </pre></div> </div> </div> <div class="section" id="replacing-functions-from-the-popen2-module"> <h3>17.5.6.6. Replacing functions from the <code class="xref py py-mod docutils literal notranslate"><span class="pre">popen2</span></code> module<a class="headerlink" href="#replacing-functions-from-the-popen2-module" title="Permalink to this headline">¶</a></h3> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">If the cmd argument to popen2 functions is a string, the command is executed through /bin/sh. If it is a list, the command is directly executed.</p> </div> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="p">(</span><span class="n">child_stdout</span><span class="p">,</span> <span class="n">child_stdin</span><span class="p">)</span> <span class="o">=</span> <span class="n">popen2</span><span class="o">.</span><span class="n">popen2</span><span class="p">(</span><span class="s2">"somestring"</span><span class="p">,</span> <span class="n">bufsize</span><span class="p">,</span> <span class="n">mode</span><span class="p">)</span> <span class="o">==></span> <span class="n">p</span> <span class="o">=</span> <span class="n">Popen</span><span class="p">(</span><span class="s2">"somestring"</span><span class="p">,</span> <span class="n">shell</span><span class="o">=</span><span class="kc">True</span><span class="p">,</span> <span class="n">bufsize</span><span class="o">=</span><span class="n">bufsize</span><span class="p">,</span> <span class="n">stdin</span><span class="o">=</span><span class="n">PIPE</span><span class="p">,</span> <span class="n">stdout</span><span class="o">=</span><span class="n">PIPE</span><span class="p">,</span> <span class="n">close_fds</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span> <span class="p">(</span><span class="n">child_stdout</span><span class="p">,</span> <span class="n">child_stdin</span><span class="p">)</span> <span class="o">=</span> <span class="p">(</span><span class="n">p</span><span class="o">.</span><span class="n">stdout</span><span class="p">,</span> <span class="n">p</span><span class="o">.</span><span class="n">stdin</span><span class="p">)</span> </pre></div> </div> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="p">(</span><span class="n">child_stdout</span><span class="p">,</span> <span class="n">child_stdin</span><span class="p">)</span> <span class="o">=</span> <span class="n">popen2</span><span class="o">.</span><span class="n">popen2</span><span class="p">([</span><span class="s2">"mycmd"</span><span class="p">,</span> <span class="s2">"myarg"</span><span class="p">],</span> <span class="n">bufsize</span><span class="p">,</span> <span class="n">mode</span><span class="p">)</span> <span class="o">==></span> <span class="n">p</span> <span class="o">=</span> <span class="n">Popen</span><span class="p">([</span><span class="s2">"mycmd"</span><span class="p">,</span> <span class="s2">"myarg"</span><span class="p">],</span> <span class="n">bufsize</span><span class="o">=</span><span class="n">bufsize</span><span class="p">,</span> <span class="n">stdin</span><span class="o">=</span><span class="n">PIPE</span><span class="p">,</span> <span class="n">stdout</span><span class="o">=</span><span class="n">PIPE</span><span class="p">,</span> <span class="n">close_fds</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span> <span class="p">(</span><span class="n">child_stdout</span><span class="p">,</span> <span class="n">child_stdin</span><span class="p">)</span> <span class="o">=</span> <span class="p">(</span><span class="n">p</span><span class="o">.</span><span class="n">stdout</span><span class="p">,</span> <span class="n">p</span><span class="o">.</span><span class="n">stdin</span><span class="p">)</span> </pre></div> </div> <p><code class="xref py py-class docutils literal notranslate"><span class="pre">popen2.Popen3</span></code> and <code class="xref py py-class docutils literal notranslate"><span class="pre">popen2.Popen4</span></code> basically work as <a class="reference internal" href="#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">subprocess.Popen</span></code></a>, except that:</p> <ul class="simple"> <li><a class="reference internal" href="#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">Popen</span></code></a> raises an exception if the execution fails.</li> <li>the <em>capturestderr</em> argument is replaced with the <em>stderr</em> argument.</li> <li><code class="docutils literal notranslate"><span class="pre">stdin=PIPE</span></code> and <code class="docutils literal notranslate"><span class="pre">stdout=PIPE</span></code> must be specified.</li> <li>popen2 closes all file descriptors by default, but you have to specify <code class="docutils literal notranslate"><span class="pre">close_fds=True</span></code> with <a class="reference internal" href="#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">Popen</span></code></a> to guarantee this behavior on all platforms or past Python versions.</li> </ul> </div> </div> <div class="section" id="legacy-shell-invocation-functions"> <h2>17.5.7. Legacy Shell Invocation Functions<a class="headerlink" href="#legacy-shell-invocation-functions" title="Permalink to this headline">¶</a></h2> <p>This module also provides the following legacy functions from the 2.x <code class="docutils literal notranslate"><span class="pre">commands</span></code> module. These operations implicitly invoke the system shell and none of the guarantees described above regarding security and exception handling consistency are valid for these functions.</p> <dl class="function"> <dt id="subprocess.getstatusoutput"> <code class="descclassname">subprocess.</code><code class="descname">getstatusoutput</code><span class="sig-paren">(</span><em>cmd</em><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.getstatusoutput" title="Permalink to this definition">¶</a></dt> <dd><p>Return <code class="docutils literal notranslate"><span class="pre">(exitcode,</span> <span class="pre">output)</span></code> of executing <em>cmd</em> in a shell.</p> <p>Execute the string <em>cmd</em> in a shell with <code class="xref py py-meth docutils literal notranslate"><span class="pre">Popen.check_output()</span></code> and return a 2-tuple <code class="docutils literal notranslate"><span class="pre">(exitcode,</span> <span class="pre">output)</span></code>. The locale encoding is used; see the notes on <a class="reference internal" href="#frequently-used-arguments"><span class="std std-ref">Frequently Used Arguments</span></a> for more details.</p> <p>A trailing newline is stripped from the output. The exit code for the command can be interpreted as the return code of subprocess. Example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">subprocess</span><span class="o">.</span><span class="n">getstatusoutput</span><span class="p">(</span><span class="s1">'ls /bin/ls'</span><span class="p">)</span> <span class="go">(0, '/bin/ls')</span> <span class="gp">>>> </span><span class="n">subprocess</span><span class="o">.</span><span class="n">getstatusoutput</span><span class="p">(</span><span class="s1">'cat /bin/junk'</span><span class="p">)</span> <span class="go">(1, 'cat: /bin/junk: No such file or directory')</span> <span class="gp">>>> </span><span class="n">subprocess</span><span class="o">.</span><span class="n">getstatusoutput</span><span class="p">(</span><span class="s1">'/bin/junk'</span><span class="p">)</span> <span class="go">(127, 'sh: /bin/junk: not found')</span> <span class="gp">>>> </span><span class="n">subprocess</span><span class="o">.</span><span class="n">getstatusoutput</span><span class="p">(</span><span class="s1">'/bin/kill $$'</span><span class="p">)</span> <span class="go">(-15, '')</span> </pre></div> </div> <p>Availability: POSIX & Windows</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.3.4: </span>Windows support was added.</p> <p>The function now returns (exitcode, output) instead of (status, output) as it did in Python 3.3.3 and earlier. exitcode has the same value as <a class="reference internal" href="#subprocess.Popen.returncode" title="subprocess.Popen.returncode"><code class="xref py py-attr docutils literal notranslate"><span class="pre">returncode</span></code></a>.</p> </div> </dd></dl> <dl class="function"> <dt id="subprocess.getoutput"> <code class="descclassname">subprocess.</code><code class="descname">getoutput</code><span class="sig-paren">(</span><em>cmd</em><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.getoutput" title="Permalink to this definition">¶</a></dt> <dd><p>Return output (stdout and stderr) of executing <em>cmd</em> in a shell.</p> <p>Like <a class="reference internal" href="#subprocess.getstatusoutput" title="subprocess.getstatusoutput"><code class="xref py py-func docutils literal notranslate"><span class="pre">getstatusoutput()</span></code></a>, except the exit code is ignored and the return value is a string containing the command’s output. Example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">subprocess</span><span class="o">.</span><span class="n">getoutput</span><span class="p">(</span><span class="s1">'ls /bin/ls'</span><span class="p">)</span> <span class="go">'/bin/ls'</span> </pre></div> </div> <p>Availability: POSIX & Windows</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.3.4: </span>Windows support added</p> </div> </dd></dl> </div> <div class="section" id="notes"> <h2>17.5.8. Notes<a class="headerlink" href="#notes" title="Permalink to this headline">¶</a></h2> <div class="section" id="converting-an-argument-sequence-to-a-string-on-windows"> <span id="converting-argument-sequence"></span><h3>17.5.8.1. Converting an argument sequence to a string on Windows<a class="headerlink" href="#converting-an-argument-sequence-to-a-string-on-windows" title="Permalink to this headline">¶</a></h3> <p>On Windows, an <em>args</em> sequence is converted to a string that can be parsed using the following rules (which correspond to the rules used by the MS C runtime):</p> <ol class="arabic simple"> <li>Arguments are delimited by white space, which is either a space or a tab.</li> <li>A string surrounded by double quotation marks is interpreted as a single argument, regardless of white space contained within. A quoted string can be embedded in an argument.</li> <li>A double quotation mark preceded by a backslash is interpreted as a literal double quotation mark.</li> <li>Backslashes are interpreted literally, unless they immediately precede a double quotation mark.</li> <li>If backslashes immediately precede a double quotation mark, every pair of backslashes is interpreted as a literal backslash. If the number of backslashes is odd, the last backslash escapes the next double quotation mark as described in rule 3.</li> </ol> <div class="admonition seealso"> <p class="first admonition-title">See also</p> <dl class="last docutils"> <dt><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></dt> <dd>Module which provides function to parse and escape command lines.</dd> </dl> </div> </div> </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="#">17.5. <code class="docutils literal notranslate"><span class="pre">subprocess</span></code> — Subprocess management</a><ul> <li><a class="reference internal" href="#using-the-subprocess-module">17.5.1. Using the <code class="docutils literal notranslate"><span class="pre">subprocess</span></code> Module</a><ul> <li><a class="reference internal" href="#frequently-used-arguments">17.5.1.1. Frequently Used Arguments</a></li> <li><a class="reference internal" href="#popen-constructor">17.5.1.2. Popen Constructor</a></li> <li><a class="reference internal" href="#exceptions">17.5.1.3. Exceptions</a></li> </ul> </li> <li><a class="reference internal" href="#security-considerations">17.5.2. Security Considerations</a></li> <li><a class="reference internal" href="#popen-objects">17.5.3. Popen Objects</a></li> <li><a class="reference internal" href="#windows-popen-helpers">17.5.4. Windows Popen Helpers</a><ul> <li><a class="reference internal" href="#constants">17.5.4.1. Constants</a></li> </ul> </li> <li><a class="reference internal" href="#older-high-level-api">17.5.5. Older high-level API</a></li> <li><a class="reference internal" href="#replacing-older-functions-with-the-subprocess-module">17.5.6. Replacing Older Functions with the <code class="docutils literal notranslate"><span class="pre">subprocess</span></code> Module</a><ul> <li><a class="reference internal" href="#replacing-bin-sh-shell-backquote">17.5.6.1. Replacing /bin/sh shell backquote</a></li> <li><a class="reference internal" href="#replacing-shell-pipeline">17.5.6.2. Replacing shell pipeline</a></li> <li><a class="reference internal" href="#replacing-os-system">17.5.6.3. Replacing <code class="docutils literal notranslate"><span class="pre">os.system()</span></code></a></li> <li><a class="reference internal" href="#replacing-the-os-spawn-family">17.5.6.4. Replacing the <code class="docutils literal notranslate"><span class="pre">os.spawn</span></code> family</a></li> <li><a class="reference internal" href="#replacing-os-popen-os-popen2-os-popen3">17.5.6.5. Replacing <code class="docutils literal notranslate"><span class="pre">os.popen()</span></code>, <code class="docutils literal notranslate"><span class="pre">os.popen2()</span></code>, <code class="docutils literal notranslate"><span class="pre">os.popen3()</span></code></a></li> <li><a class="reference internal" href="#replacing-functions-from-the-popen2-module">17.5.6.6. Replacing functions from the <code class="docutils literal notranslate"><span class="pre">popen2</span></code> module</a></li> </ul> </li> <li><a class="reference internal" href="#legacy-shell-invocation-functions">17.5.7. Legacy Shell Invocation Functions</a></li> <li><a class="reference internal" href="#notes">17.5.8. Notes</a><ul> <li><a class="reference internal" href="#converting-an-argument-sequence-to-a-string-on-windows">17.5.8.1. Converting an argument sequence to a string on Windows</a></li> </ul> </li> </ul> </li> </ul> <h4>Previous topic</h4> <p class="topless"><a href="concurrent.futures.html" title="previous chapter">17.4. <code class="docutils literal notranslate"><span class="pre">concurrent.futures</span></code> — Launching parallel tasks</a></p> <h4>Next topic</h4> <p class="topless"><a href="sched.html" title="next chapter">17.6. <code class="docutils literal notranslate"><span class="pre">sched</span></code> — Event scheduler</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/3.6/Doc/library/subprocess.rst" rel="nofollow">Show Source </a> </li> </ul> </div> </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="sched.html" title="17.6. sched — Event scheduler" >next</a> |</li> <li class="right" > <a href="concurrent.futures.html" title="17.4. concurrent.futures — Launching parallel tasks" >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">3.6.7 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="concurrency.html" >17. 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