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  98. <li><a class="reference internal" href="#"><code class="xref py py-mod docutils literal notranslate"><span class="pre">subprocess</span></code> — Subprocess management</a><ul>

  99. <li><a class="reference internal" href="#using-the-subprocess-module">Using the <code class="xref py py-mod docutils literal notranslate"><span class="pre">subprocess</span></code> Module</a><ul>

  100. <li><a class="reference internal" href="#frequently-used-arguments">Frequently Used Arguments</a></li>

  101. <li><a class="reference internal" href="#popen-constructor">Popen Constructor</a></li>

  102. <li><a class="reference internal" href="#exceptions">Exceptions</a></li>

  103. </ul>

  104. </li>

  105. <li><a class="reference internal" href="#security-considerations">Security Considerations</a></li>

  106. <li><a class="reference internal" href="#popen-objects">Popen Objects</a></li>

  107. <li><a class="reference internal" href="#windows-popen-helpers">Windows Popen Helpers</a><ul>

  108. <li><a class="reference internal" href="#windows-constants">Windows Constants</a></li>

  109. </ul>

  110. </li>

  111. <li><a class="reference internal" href="#older-high-level-api">Older high-level API</a></li>

  112. <li><a class="reference internal" href="#replacing-older-functions-with-the-subprocess-module">Replacing Older Functions with the <code class="xref py py-mod docutils literal notranslate"><span class="pre">subprocess</span></code> Module</a><ul>

  113. <li><a class="reference internal" href="#replacing-bin-sh-shell-command-substitution">Replacing <strong class="program">/bin/sh</strong> shell command substitution</a></li>

  114. <li><a class="reference internal" href="#replacing-shell-pipeline">Replacing shell pipeline</a></li>

  115. <li><a class="reference internal" href="#replacing-os-system">Replacing <code class="xref py py-func docutils literal notranslate"><span class="pre">os.system()</span></code></a></li>

  116. <li><a class="reference internal" href="#replacing-the-os-spawn-family">Replacing the <code class="xref py py-func docutils literal notranslate"><span class="pre">os.spawn</span></code> family</a></li>

  117. <li><a class="reference internal" href="#replacing-os-popen-os-popen2-os-popen3">Replacing <code class="xref py py-func docutils literal notranslate"><span class="pre">os.popen()</span></code>, <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></li>

  118. <li><a class="reference internal" href="#replacing-functions-from-the-popen2-module">Replacing functions from the <code class="xref py py-mod docutils literal notranslate"><span class="pre">popen2</span></code> module</a></li>

  119. </ul>

  120. </li>

  121. <li><a class="reference internal" href="#legacy-shell-invocation-functions">Legacy Shell Invocation Functions</a></li>

  122. <li><a class="reference internal" href="#notes">Notes</a><ul>

  123. <li><a class="reference internal" href="#converting-an-argument-sequence-to-a-string-on-windows">Converting an argument sequence to a string on Windows</a></li>

  124. <li><a class="reference internal" href="#disabling-use-of-vfork-or-posix-spawn">Disabling use of <code class="docutils literal notranslate"><span class="pre">vfork()</span></code> or <code class="docutils literal notranslate"><span class="pre">posix_spawn()</span></code></a></li>

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  219.   <section id="module-subprocess">

  220. <span id="subprocess-subprocess-management"></span><h1><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="Link to this heading">¶</a></h1>

  221. <p><strong>Source code:</strong> <a class="reference external" href="https://github.com/python/cpython/tree/3.12/Lib/subprocess.py">Lib/subprocess.py</a></p>

  222. <hr class="docutils" />

  223. <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

  224. input/output/error pipes, and obtain their return codes.  This module intends to

  225. replace several older modules and functions:</p>

  226. <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>

  227. <span class="n">os</span><span class="o">.</span><span class="n">spawn</span><span class="o">*</span>

  228. </pre></div>

  229. </div>

  230. <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

  231. modules and functions can be found in the following sections.</p>

  232. <div class="admonition seealso">

  233. <p class="admonition-title">See also</p>

  234. <p><span class="target" id="index-0"></span><a class="pep reference external" href="https://peps.python.org/pep-0324/"><strong>PEP 324</strong></a> – PEP proposing the subprocess module</p>

  235. </div>

  236. <div class="availability docutils container">

  237. <p><a class="reference internal" href="intro.html#availability"><span class="std std-ref">Availability</span></a>: not Emscripten, not WASI.</p>

  238. <p>This module does not work or is not available on WebAssembly platforms

  239. <code class="docutils literal notranslate"><span class="pre">wasm32-emscripten</span></code> and <code class="docutils literal notranslate"><span class="pre">wasm32-wasi</span></code>. See

  240. <a class="reference internal" href="intro.html#wasm-availability"><span class="std std-ref">WebAssembly platforms</span></a> for more information.</p>

  241. </div>

  242. <section id="using-the-subprocess-module">

  243. <h2>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="Link to this heading">¶</a></h2>

  244. <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>

  245. function for all use cases it can handle. For more advanced use cases, the

  246. 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>

  247. <dl class="py function">

  248. <dt class="sig sig-object py" id="subprocess.run">

  249. <span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">run</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">args</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">*</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">stdin</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">input</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">stdout</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">stderr</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">capture_output</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">False</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">shell</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">False</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">cwd</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">timeout</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">check</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">False</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">encoding</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">errors</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">text</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">env</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">universal_newlines</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">**</span></span><span class="n"><span class="pre">other_popen_kwargs</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.run" title="Link to this definition">¶</a></dt>

  250. <dd><p>Run the command described by <em>args</em>.  Wait for command to complete, then

  251. 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>

  252. <p>The arguments shown above are merely the most common ones, described below

  253. 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

  254. in the abbreviated signature). The full function signature is largely the

  255. 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 - most of the arguments to

  256. this function are passed through to that interface. (<em>timeout</em>,  <em>input</em>,

  257. <em>check</em>, and <em>capture_output</em> are not.)</p>

  258. <p>If <em>capture_output</em> is true, stdout and stderr will be captured.

  259. 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

  260. <em>stdout</em> and <em>stdin</em> both set to <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>.

  261. The <em>stdout</em> and <em>stderr</em> arguments may not be supplied at the same time as <em>capture_output</em>.

  262. If you wish to capture and combine both streams into one,

  263. set <em>stdout</em> to <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>

  264. and <em>stderr</em> to <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>,

  265. instead of using <em>capture_output</em>.</p>

  266. <p>A <em>timeout</em> may be specified in seconds, it is internally passed on to

  267. <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

  268. 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

  269. re-raised after the child process has terminated. The initial process

  270. creation itself cannot be interrupted on many platform APIs so you are not

  271. guaranteed to see a timeout exception until at least after however long

  272. process creation takes.</p>

  273. <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

  274. subprocess’s stdin.  If used it must be a byte sequence, or a string if

  275. <em>encoding</em> or <em>errors</em> is specified or <em>text</em> is true.  When

  276. 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

  277. <em>stdin</em> set to <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>,

  278. and the <em>stdin</em> argument may not be used as well.</p>

  279. <p>If <em>check</em> is true, and the process exits with a non-zero exit code, a

  280. <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

  281. exception hold the arguments, the exit code, and stdout and stderr if they

  282. were captured.</p>

  283. <p>If <em>encoding</em> or <em>errors</em> are specified, or <em>text</em> is true,

  284. file objects for stdin, stdout and stderr are opened in text mode using the

  285. 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.

  286. The <em>universal_newlines</em> argument is equivalent  to <em>text</em> and is provided

  287. for backwards compatibility. By default, file objects are opened in binary mode.</p>

  288. <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

  289. variables for the new process; these are used instead of the default

  290. behavior of inheriting the current process’ environment. It is passed

  291. 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>. This mapping can be str to str on any platform

  292. or bytes to bytes on POSIX platforms much like <a class="reference internal" href="os.html#os.environ" title="os.environ"><code class="xref py py-data docutils literal notranslate"><span class="pre">os.environ</span></code></a> or

  293. <a class="reference internal" href="os.html#os.environb" title="os.environb"><code class="xref py py-data docutils literal notranslate"><span class="pre">os.environb</span></code></a>.</p>

  294. <p>Examples:</p>

  295. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">subprocess</span><span class="o">.</span><span class="n">run</span><span class="p">([</span><span class="s2">&quot;ls&quot;</span><span class="p">,</span> <span class="s2">&quot;-l&quot;</span><span class="p">])</span>  <span class="c1"># doesn&#39;t capture output</span>

  296. <span class="go">CompletedProcess(args=[&#39;ls&#39;, &#39;-l&#39;], returncode=0)</span>

  297. 

  298. <span class="gp">&gt;&gt;&gt; </span><span class="n">subprocess</span><span class="o">.</span><span class="n">run</span><span class="p">(</span><span class="s2">&quot;exit 1&quot;</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>

  299. <span class="gt">Traceback (most recent call last):</span>

  300. <span class="w">  </span><span class="c">...</span>

  301. <span class="gr">subprocess.CalledProcessError</span>: <span class="n">Command &#39;exit 1&#39; returned non-zero exit status 1</span>

  302. 

  303. <span class="gp">&gt;&gt;&gt; </span><span class="n">subprocess</span><span class="o">.</span><span class="n">run</span><span class="p">([</span><span class="s2">&quot;ls&quot;</span><span class="p">,</span> <span class="s2">&quot;-l&quot;</span><span class="p">,</span> <span class="s2">&quot;/dev/null&quot;</span><span class="p">],</span> <span class="n">capture_output</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>

  304. <span class="go">CompletedProcess(args=[&#39;ls&#39;, &#39;-l&#39;, &#39;/dev/null&#39;], returncode=0,</span>

  305. <span class="go">stdout=b&#39;crw-rw-rw- 1 root root 1, 3 Jan 23 16:23 /dev/null\n&#39;, stderr=b&#39;&#39;)</span>

  306. </pre></div>

  307. </div>

  308. <div class="versionadded">

  309. <p><span class="versionmodified added">New in version 3.5.</span></p>

  310. </div>

  311. <div class="versionchanged">

  312. <p><span class="versionmodified changed">Changed in version 3.6: </span>Added <em>encoding</em> and <em>errors</em> parameters</p>

  313. </div>

  314. <div class="versionchanged">

  315. <p><span class="versionmodified changed">Changed in version 3.7: </span>Added the <em>text</em> parameter, as a more understandable alias of <em>universal_newlines</em>.

  316. Added the <em>capture_output</em> parameter.</p>

  317. </div>

  318. <div class="versionchanged">

  319. <p><span class="versionmodified changed">Changed in version 3.12: </span>Changed Windows shell search order for <code class="docutils literal notranslate"><span class="pre">shell=True</span></code>. The current

  320. directory and <code class="docutils literal notranslate"><span class="pre">%PATH%</span></code> are replaced with <code class="docutils literal notranslate"><span class="pre">%COMSPEC%</span></code> and

  321. <code class="docutils literal notranslate"><span class="pre">%SystemRoot%\System32\cmd.exe</span></code>. As a result, dropping a

  322. malicious program named <code class="docutils literal notranslate"><span class="pre">cmd.exe</span></code> into a current directory no

  323. longer works.</p>

  324. </div>

  325. </dd></dl>

  326. 

  327. <dl class="py class">

  328. <dt class="sig sig-object py" id="subprocess.CompletedProcess">

  329. <em class="property"><span class="pre">class</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">CompletedProcess</span></span><a class="headerlink" href="#subprocess.CompletedProcess" title="Link to this definition">¶</a></dt>

  330. <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>

  331. <dl class="py attribute">

  332. <dt class="sig sig-object py" id="subprocess.CompletedProcess.args">

  333. <span class="sig-name descname"><span class="pre">args</span></span><a class="headerlink" href="#subprocess.CompletedProcess.args" title="Link to this definition">¶</a></dt>

  334. <dd><p>The arguments used to launch the process. This may be a list or a string.</p>

  335. </dd></dl>

  336. 

  337. <dl class="py attribute">

  338. <dt class="sig sig-object py" id="subprocess.CompletedProcess.returncode">

  339. <span class="sig-name descname"><span class="pre">returncode</span></span><a class="headerlink" href="#subprocess.CompletedProcess.returncode" title="Link to this definition">¶</a></dt>

  340. <dd><p>Exit status of the child process. Typically, an exit status of 0 indicates

  341. that it ran successfully.</p>

  342. <p>A negative value <code class="docutils literal notranslate"><span class="pre">-N</span></code> indicates that the child was terminated by signal

  343. <code class="docutils literal notranslate"><span class="pre">N</span></code> (POSIX only).</p>

  344. </dd></dl>

  345. 

  346. <dl class="py attribute">

  347. <dt class="sig sig-object py" id="subprocess.CompletedProcess.stdout">

  348. <span class="sig-name descname"><span class="pre">stdout</span></span><a class="headerlink" href="#subprocess.CompletedProcess.stdout" title="Link to this definition">¶</a></dt>

  349. <dd><p>Captured stdout from the child process. A bytes sequence, or a string if

  350. <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, errors, or text=True.

  351. <code class="docutils literal notranslate"><span class="pre">None</span></code> if stdout was not captured.</p>

  352. <p>If you ran the process with <code class="docutils literal notranslate"><span class="pre">stderr=subprocess.STDOUT</span></code>, stdout and

  353. 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

  354. <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p>

  355. </dd></dl>

  356. 

  357. <dl class="py attribute">

  358. <dt class="sig sig-object py" id="subprocess.CompletedProcess.stderr">

  359. <span class="sig-name descname"><span class="pre">stderr</span></span><a class="headerlink" href="#subprocess.CompletedProcess.stderr" title="Link to this definition">¶</a></dt>

  360. <dd><p>Captured stderr from the child process. A bytes sequence, or a string if

  361. <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, errors, or text=True.

  362. <code class="docutils literal notranslate"><span class="pre">None</span></code> if stderr was not captured.</p>

  363. </dd></dl>

  364. 

  365. <dl class="py method">

  366. <dt class="sig sig-object py" id="subprocess.CompletedProcess.check_returncode">

  367. <span class="sig-name descname"><span class="pre">check_returncode</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.CompletedProcess.check_returncode" title="Link to this definition">¶</a></dt>

  368. <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>

  369. </dd></dl>

  370. 

  371. <div class="versionadded">

  372. <p><span class="versionmodified added">New in version 3.5.</span></p>

  373. </div>

  374. </dd></dl>

  375. 

  376. <dl class="py data">

  377. <dt class="sig sig-object py" id="subprocess.DEVNULL">

  378. <span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">DEVNULL</span></span><a class="headerlink" href="#subprocess.DEVNULL" title="Link to this definition">¶</a></dt>

  379. <dd><p>Special value that can be used as the <em>stdin</em>, <em>stdout</em> or <em>stderr</em> argument

  380. 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>

  381. will be used.</p>

  382. <div class="versionadded">

  383. <p><span class="versionmodified added">New in version 3.3.</span></p>

  384. </div>

  385. </dd></dl>

  386. 

  387. <dl class="py data">

  388. <dt class="sig sig-object py" id="subprocess.PIPE">

  389. <span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">PIPE</span></span><a class="headerlink" href="#subprocess.PIPE" title="Link to this definition">¶</a></dt>

  390. <dd><p>Special value that can be used as the <em>stdin</em>, <em>stdout</em> or <em>stderr</em> argument

  391. 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

  392. 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>

  393. </dd></dl>

  394. 

  395. <dl class="py data">

  396. <dt class="sig sig-object py" id="subprocess.STDOUT">

  397. <span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">STDOUT</span></span><a class="headerlink" href="#subprocess.STDOUT" title="Link to this definition">¶</a></dt>

  398. <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

  399. indicates that standard error should go into the same handle as standard

  400. output.</p>

  401. </dd></dl>

  402. 

  403. <dl class="py exception">

  404. <dt class="sig sig-object py" id="subprocess.SubprocessError">

  405. <em class="property"><span class="pre">exception</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">SubprocessError</span></span><a class="headerlink" href="#subprocess.SubprocessError" title="Link to this definition">¶</a></dt>

  406. <dd><p>Base class for all other exceptions from this module.</p>

  407. <div class="versionadded">

  408. <p><span class="versionmodified added">New in version 3.3.</span></p>

  409. </div>

  410. </dd></dl>

  411. 

  412. <dl class="py exception">

  413. <dt class="sig sig-object py" id="subprocess.TimeoutExpired">

  414. <em class="property"><span class="pre">exception</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">TimeoutExpired</span></span><a class="headerlink" href="#subprocess.TimeoutExpired" title="Link to this definition">¶</a></dt>

  415. <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

  416. while waiting for a child process.</p>

  417. <dl class="py attribute">

  418. <dt class="sig sig-object py" id="subprocess.TimeoutExpired.cmd">

  419. <span class="sig-name descname"><span class="pre">cmd</span></span><a class="headerlink" href="#subprocess.TimeoutExpired.cmd" title="Link to this definition">¶</a></dt>

  420. <dd><p>Command that was used to spawn the child process.</p>

  421. </dd></dl>

  422. 

  423. <dl class="py attribute">

  424. <dt class="sig sig-object py" id="subprocess.TimeoutExpired.timeout">

  425. <span class="sig-name descname"><span class="pre">timeout</span></span><a class="headerlink" href="#subprocess.TimeoutExpired.timeout" title="Link to this definition">¶</a></dt>

  426. <dd><p>Timeout in seconds.</p>

  427. </dd></dl>

  428. 

  429. <dl class="py attribute">

  430. <dt class="sig sig-object py" id="subprocess.TimeoutExpired.output">

  431. <span class="sig-name descname"><span class="pre">output</span></span><a class="headerlink" href="#subprocess.TimeoutExpired.output" title="Link to this definition">¶</a></dt>

  432. <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

  433. <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>.  This is always

  434. <a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> when any output was captured regardless of the

  435. <code class="docutils literal notranslate"><span class="pre">text=True</span></code> setting.  It may remain <code class="docutils literal notranslate"><span class="pre">None</span></code> instead of <code class="docutils literal notranslate"><span class="pre">b''</span></code>

  436. when no output was observed.</p>

  437. </dd></dl>

  438. 

  439. <dl class="py attribute">

  440. <dt class="sig sig-object py" id="subprocess.TimeoutExpired.stdout">

  441. <span class="sig-name descname"><span class="pre">stdout</span></span><a class="headerlink" href="#subprocess.TimeoutExpired.stdout" title="Link to this definition">¶</a></dt>

  442. <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>

  443. </dd></dl>

  444. 

  445. <dl class="py attribute">

  446. <dt class="sig sig-object py" id="subprocess.TimeoutExpired.stderr">

  447. <span class="sig-name descname"><span class="pre">stderr</span></span><a class="headerlink" href="#subprocess.TimeoutExpired.stderr" title="Link to this definition">¶</a></dt>

  448. <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>.

  449. Otherwise, <code class="docutils literal notranslate"><span class="pre">None</span></code>.  This is always <a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> when stderr output

  450. was captured regardless of the <code class="docutils literal notranslate"><span class="pre">text=True</span></code> setting.  It may remain

  451. <code class="docutils literal notranslate"><span class="pre">None</span></code> instead of <code class="docutils literal notranslate"><span class="pre">b''</span></code> when no stderr output was observed.</p>

  452. </dd></dl>

  453. 

  454. <div class="versionadded">

  455. <p><span class="versionmodified added">New in version 3.3.</span></p>

  456. </div>

  457. <div class="versionchanged">

  458. <p><span class="versionmodified changed">Changed in version 3.5: </span><em>stdout</em> and <em>stderr</em> attributes added</p>

  459. </div>

  460. </dd></dl>

  461. 

  462. <dl class="py exception">

  463. <dt class="sig sig-object py" id="subprocess.CalledProcessError">

  464. <em class="property"><span class="pre">exception</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">CalledProcessError</span></span><a class="headerlink" href="#subprocess.CalledProcessError" title="Link to this definition">¶</a></dt>

  465. <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

  466. <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>, <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>, or <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> (with <code class="docutils literal notranslate"><span class="pre">check=True</span></code>)

  467. returns a non-zero exit status.</p>

  468. <dl class="py attribute">

  469. <dt class="sig sig-object py" id="subprocess.CalledProcessError.returncode">

  470. <span class="sig-name descname"><span class="pre">returncode</span></span><a class="headerlink" href="#subprocess.CalledProcessError.returncode" title="Link to this definition">¶</a></dt>

  471. <dd><p>Exit status of the child process.  If the process exited due to a

  472. signal, this will be the negative signal number.</p>

  473. </dd></dl>

  474. 

  475. <dl class="py attribute">

  476. <dt class="sig sig-object py" id="subprocess.CalledProcessError.cmd">

  477. <span class="sig-name descname"><span class="pre">cmd</span></span><a class="headerlink" href="#subprocess.CalledProcessError.cmd" title="Link to this definition">¶</a></dt>

  478. <dd><p>Command that was used to spawn the child process.</p>

  479. </dd></dl>

  480. 

  481. <dl class="py attribute">

  482. <dt class="sig sig-object py" id="subprocess.CalledProcessError.output">

  483. <span class="sig-name descname"><span class="pre">output</span></span><a class="headerlink" href="#subprocess.CalledProcessError.output" title="Link to this definition">¶</a></dt>

  484. <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

  485. <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>

  486. </dd></dl>

  487. 

  488. <dl class="py attribute">

  489. <dt class="sig sig-object py" id="subprocess.CalledProcessError.stdout">

  490. <span class="sig-name descname"><span class="pre">stdout</span></span><a class="headerlink" href="#subprocess.CalledProcessError.stdout" title="Link to this definition">¶</a></dt>

  491. <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>

  492. </dd></dl>

  493. 

  494. <dl class="py attribute">

  495. <dt class="sig sig-object py" id="subprocess.CalledProcessError.stderr">

  496. <span class="sig-name descname"><span class="pre">stderr</span></span><a class="headerlink" href="#subprocess.CalledProcessError.stderr" title="Link to this definition">¶</a></dt>

  497. <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>.

  498. Otherwise, <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p>

  499. </dd></dl>

  500. 

  501. <div class="versionchanged">

  502. <p><span class="versionmodified changed">Changed in version 3.5: </span><em>stdout</em> and <em>stderr</em> attributes added</p>

  503. </div>

  504. </dd></dl>

  505. 

  506. <section id="frequently-used-arguments">

  507. <span id="id1"></span><h3>Frequently Used Arguments<a class="headerlink" href="#frequently-used-arguments" title="Link to this heading">¶</a></h3>

  508. <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

  509. the convenience functions) accept a large number of optional arguments. For

  510. most typical use cases, many of these arguments can be safely left at their

  511. default values. The arguments that are most commonly needed are:</p>

  512. <blockquote>

  513. <div><p><em>args</em> is required for all calls and should be a string, or a sequence of

  514. program arguments. Providing a sequence of arguments is generally

  515. preferred, as it allows the module to take care of any required escaping

  516. and quoting of arguments (e.g. to permit spaces in file names). If passing

  517. 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

  518. the string must simply name the program to be executed without specifying

  519. any arguments.</p>

  520. <p><em>stdin</em>, <em>stdout</em> and <em>stderr</em> specify the executed program’s standard input,

  521. standard output and standard error file handles, respectively.  Valid values

  522. are <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>, <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

  523. positive integer), and an existing <a class="reference internal" href="../glossary.html#term-file-object"><span class="xref std std-term">file object</span></a> with a valid file

  524. descriptor.  With the default settings of <code class="docutils literal notranslate"><span class="pre">None</span></code>, no redirection will

  525. occur.  <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

  526. 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>

  527. will be used.  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

  528. that the stderr data from the child process should be captured into the same

  529. file handle as for <em>stdout</em>.</p>

  530. <p id="index-1">If <em>encoding</em> or <em>errors</em> are specified, or <em>text</em> (also known as

  531. <em>universal_newlines</em>) is true,

  532. the file objects <em>stdin</em>, <em>stdout</em> and <em>stderr</em> will be opened in text

  533. mode using the <em>encoding</em> and <em>errors</em> specified in the call or the

  534. 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>

  535. <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

  536. 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>,

  537. all line endings in the output will be converted to <code class="docutils literal notranslate"><span class="pre">'\n'</span></code>.  For more

  538. 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

  539. when the <em>newline</em> argument to its constructor is <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p>

  540. <p>If text mode is not used, <em>stdin</em>, <em>stdout</em> and <em>stderr</em> will be opened as

  541. binary streams. No encoding or line ending conversion is performed.</p>

  542. <div class="versionchanged">

  543. <p><span class="versionmodified changed">Changed in version 3.6: </span>Added the <em>encoding</em> and <em>errors</em> parameters.</p>

  544. </div>

  545. <div class="versionchanged">

  546. <p><span class="versionmodified changed">Changed in version 3.7: </span>Added the <em>text</em> parameter as an alias for <em>universal_newlines</em>.</p>

  547. </div>

  548. <div class="admonition note">

  549. <p class="admonition-title">Note</p>

  550. <p>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>,

  551. <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

  552. 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>

  553. </div>

  554. <p>If <em>shell</em> is <code class="docutils literal notranslate"><span class="pre">True</span></code>, the specified command will be executed through

  555. the shell.  This can be useful if you are using Python primarily for the

  556. enhanced control flow it offers over most system shells and still want

  557. convenient access to other shell features such as shell pipes, filename

  558. wildcards, environment variable expansion, and expansion of <code class="docutils literal notranslate"><span class="pre">~</span></code> to a

  559. user’s home directory.  However, note that Python itself offers

  560. 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>,

  561. <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>,

  562. <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>

  563. <div class="versionchanged">

  564. <p><span class="versionmodified changed">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

  565. <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>

  566. instead of <code class="docutils literal notranslate"><span class="pre">locale.getpreferredencoding()</span></code>.  See the

  567. <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>

  568. </div>

  569. <div class="admonition note">

  570. <p class="admonition-title">Note</p>

  571. <p>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>

  572. </div>

  573. </div></blockquote>

  574. <p>These options, along with all of the other options, are described in more

  575. 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>

  576. </section>

  577. <section id="popen-constructor">

  578. <h3>Popen Constructor<a class="headerlink" href="#popen-constructor" title="Link to this heading">¶</a></h3>

  579. <p>The underlying process creation and management in this module is handled by

  580. 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

  581. are able to handle the less common cases not covered by the convenience

  582. functions.</p>

  583. <dl class="py class">

  584. <dt class="sig sig-object py" id="subprocess.Popen">

  585. <em class="property"><span class="pre">class</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">Popen</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">args</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">bufsize</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">-1</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">executable</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">stdin</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">stdout</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">stderr</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">preexec_fn</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">close_fds</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">True</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">shell</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">False</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">cwd</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">env</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">universal_newlines</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">startupinfo</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">creationflags</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">0</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">restore_signals</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">True</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">start_new_session</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">False</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">pass_fds</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">()</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">*</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">group</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">extra_groups</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">user</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">umask</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">-1</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">encoding</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">errors</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">text</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">pipesize</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">-1</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">process_group</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.Popen" title="Link to this definition">¶</a></dt>

  586. <dd><p>Execute a child program in a new process.  On POSIX, the class uses

  587. <a class="reference internal" href="os.html#os.execvpe" title="os.execvpe"><code class="xref py py-meth docutils literal notranslate"><span class="pre">os.execvpe()</span></code></a>-like behavior to execute the child program.  On Windows,

  588. the class uses the Windows <code class="docutils literal notranslate"><span class="pre">CreateProcess()</span></code> function.  The arguments to

  589. <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>

  590. <p><em>args</em> should be a sequence of program arguments or else a single string

  591. or <a class="reference internal" href="../glossary.html#term-path-like-object"><span class="xref std std-term">path-like object</span></a>.

  592. By default, the program to execute is the first item in <em>args</em> if <em>args</em> is

  593. a sequence.  If <em>args</em> is a string, the interpretation is

  594. platform-dependent and described below.  See the <em>shell</em> and <em>executable</em>

  595. arguments for additional differences from the default behavior.  Unless

  596. otherwise stated, it is recommended to pass <em>args</em> as a sequence.</p>

  597. <div class="admonition warning">

  598. <p class="admonition-title">Warning</p>

  599. <p>For maximum reliability, use a fully qualified path for the executable.

  600. To search for an unqualified name on <span class="target" id="index-2"></span><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PATH</span></code>, use

  601. <a class="reference internal" href="shutil.html#shutil.which" title="shutil.which"><code class="xref py py-meth docutils literal notranslate"><span class="pre">shutil.which()</span></code></a>. On all platforms, passing <a class="reference internal" href="sys.html#sys.executable" title="sys.executable"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.executable</span></code></a>

  602. is the recommended way to launch the current Python interpreter again,

  603. and use the <code class="docutils literal notranslate"><span class="pre">-m</span></code> command-line format to launch an installed module.</p>

  604. <p>Resolving the path of <em>executable</em> (or the first item of <em>args</em>) is

  605. platform dependent. For POSIX, see <a class="reference internal" href="os.html#os.execvpe" title="os.execvpe"><code class="xref py py-meth docutils literal notranslate"><span class="pre">os.execvpe()</span></code></a>, and note that

  606. when resolving or searching for the executable path, <em>cwd</em> overrides the

  607. current working directory and <em>env</em> can override the <code class="docutils literal notranslate"><span class="pre">PATH</span></code>

  608. environment variable. For Windows, see the documentation of the

  609. <code class="docutils literal notranslate"><span class="pre">lpApplicationName</span></code> and <code class="docutils literal notranslate"><span class="pre">lpCommandLine</span></code> parameters of WinAPI

  610. <code class="docutils literal notranslate"><span class="pre">CreateProcess</span></code>, and note that when resolving or searching for the

  611. executable path with <code class="docutils literal notranslate"><span class="pre">shell=False</span></code>, <em>cwd</em> does not override the

  612. current working directory and <em>env</em> cannot override the <code class="docutils literal notranslate"><span class="pre">PATH</span></code>

  613. environment variable. Using a full path avoids all of these variations.</p>

  614. </div>

  615. <p>An example of passing some arguments to an external program

  616. as a sequence is:</p>

  617. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">Popen</span><span class="p">([</span><span class="s2">&quot;/usr/bin/git&quot;</span><span class="p">,</span> <span class="s2">&quot;commit&quot;</span><span class="p">,</span> <span class="s2">&quot;-m&quot;</span><span class="p">,</span> <span class="s2">&quot;Fixes a bug.&quot;</span><span class="p">])</span>

  618. </pre></div>

  619. </div>

  620. <p>On POSIX, if <em>args</em> is a string, the string is interpreted as the name or

  621. path of the program to execute.  However, this can only be done if not

  622. passing arguments to the program.</p>

  623. <div class="admonition note">

  624. <p class="admonition-title">Note</p>

  625. <p>It may not be obvious how to break a shell command into a sequence of arguments,

  626. especially in complex cases. <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 illustrate how to

  627. determine the correct tokenization for <em>args</em>:</p>

  628. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="kn">import</span> <span class="nn">shlex</span><span class="o">,</span> <span class="nn">subprocess</span>

  629. <span class="gp">&gt;&gt;&gt; </span><span class="n">command_line</span> <span class="o">=</span> <span class="nb">input</span><span class="p">()</span>

  630. <span class="go">/bin/vikings -input eggs.txt -output &quot;spam spam.txt&quot; -cmd &quot;echo &#39;$MONEY&#39;&quot;</span>

  631. <span class="gp">&gt;&gt;&gt; </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>

  632. <span class="gp">&gt;&gt;&gt; </span><span class="nb">print</span><span class="p">(</span><span class="n">args</span><span class="p">)</span>

  633. <span class="go">[&#39;/bin/vikings&#39;, &#39;-input&#39;, &#39;eggs.txt&#39;, &#39;-output&#39;, &#39;spam spam.txt&#39;, &#39;-cmd&#39;, &quot;echo &#39;$MONEY&#39;&quot;]</span>

  634. <span class="gp">&gt;&gt;&gt; </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>

  635. </pre></div>

  636. </div>

  637. <p>Note in particular that options (such as <em>-input</em>) and arguments (such

  638. as <em>eggs.txt</em>) that are separated by whitespace in the shell go in separate

  639. list elements, while arguments that need quoting or backslash escaping when

  640. used in the shell (such as filenames containing spaces or the <em>echo</em> command

  641. shown above) are single list elements.</p>

  642. </div>

  643. <p>On Windows, if <em>args</em> is a sequence, it will be converted to a string in a

  644. 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

  645. the underlying <code class="docutils literal notranslate"><span class="pre">CreateProcess()</span></code> operates on strings.</p>

  646. <div class="versionchanged">

  647. <p><span class="versionmodified changed">Changed in version 3.6: </span><em>args</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> if <em>shell</em> is

  648. <code class="docutils literal notranslate"><span class="pre">False</span></code> and a sequence containing path-like objects on POSIX.</p>

  649. </div>

  650. <div class="versionchanged">

  651. <p><span class="versionmodified changed">Changed in version 3.8: </span><em>args</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> if <em>shell</em> is

  652. <code class="docutils literal notranslate"><span class="pre">False</span></code> and a sequence containing bytes and path-like objects

  653. on Windows.</p>

  654. </div>

  655. <p>The <em>shell</em> argument (which defaults to <code class="docutils literal notranslate"><span class="pre">False</span></code>) specifies whether to use

  656. 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

  657. recommended to pass <em>args</em> as a string rather than as a sequence.</p>

  658. <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

  659. <em>args</em> is a string, the string specifies the command

  660. to execute through the shell.  This means that the string must be

  661. formatted exactly as it would be when typed at the shell prompt.  This

  662. includes, for example, quoting or backslash escaping filenames with spaces in

  663. them.  If <em>args</em> is a sequence, the first item specifies the command string, and

  664. any additional items will be treated as additional arguments to the shell

  665. 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>

  666. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">Popen</span><span class="p">([</span><span class="s1">&#39;/bin/sh&#39;</span><span class="p">,</span> <span class="s1">&#39;-c&#39;</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>

  667. </pre></div>

  668. </div>

  669. <p>On Windows with <code class="docutils literal notranslate"><span class="pre">shell=True</span></code>, the <span class="target" id="index-3"></span><code class="xref std std-envvar docutils literal notranslate"><span class="pre">COMSPEC</span></code> environment variable

  670. specifies the default shell.  The only time you need to specify

  671. <code class="docutils literal notranslate"><span class="pre">shell=True</span></code> on Windows is when the command you wish to execute is built

  672. into the shell (e.g. <strong class="command">dir</strong> or <strong class="command">copy</strong>).  You do not need

  673. <code class="docutils literal notranslate"><span class="pre">shell=True</span></code> to run a batch file or console-based executable.</p>

  674. <div class="admonition note">

  675. <p class="admonition-title">Note</p>

  676. <p>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>

  677. </div>

  678. <p><em>bufsize</em> will be supplied as the corresponding argument to the

  679. <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

  680. file objects:</p>

  681. <ul class="simple">

  682. <li><p><code class="docutils literal notranslate"><span class="pre">0</span></code> means unbuffered (read and write are one

  683. system call and can return short)</p></li>

  684. <li><p><code class="docutils literal notranslate"><span class="pre">1</span></code> means line buffered

  685. (only usable if <code class="docutils literal notranslate"><span class="pre">text=True</span></code> or <code class="docutils literal notranslate"><span class="pre">universal_newlines=True</span></code>)</p></li>

  686. <li><p>any other positive value means use a buffer of approximately that

  687. size</p></li>

  688. <li><p>negative bufsize (the default) means the system default of

  689. io.DEFAULT_BUFFER_SIZE will be used.</p></li>

  690. </ul>

  691. <div class="versionchanged">

  692. <p><span class="versionmodified changed">Changed in version 3.3.1: </span><em>bufsize</em> now defaults to -1 to enable buffering by default to match the

  693. behavior that most code expects.  In versions prior to Python 3.2.4 and

  694. 3.3.1 it incorrectly defaulted to <code class="docutils literal notranslate"><span class="pre">0</span></code> which was unbuffered

  695. and allowed short reads.  This was unintentional and did not match the

  696. behavior of Python 2 as most code expected.</p>

  697. </div>

  698. <p>The <em>executable</em> argument specifies a replacement program to execute.   It

  699. is very seldom needed.  When <code class="docutils literal notranslate"><span class="pre">shell=False</span></code>, <em>executable</em> replaces the

  700. program to execute specified by <em>args</em>.  However, the original <em>args</em> is

  701. still passed to the program.  Most programs treat the program specified

  702. by <em>args</em> as the command name, which can then be different from the program

  703. actually executed.  On POSIX, the <em>args</em> name

  704. becomes the display name for the executable in utilities such as

  705. <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

  706. specifies a replacement shell for the default <code class="file docutils literal notranslate"><span class="pre">/bin/sh</span></code>.</p>

  707. <div class="versionchanged">

  708. <p><span class="versionmodified changed">Changed in version 3.6: </span><em>executable</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> on POSIX.</p>

  709. </div>

  710. <div class="versionchanged">

  711. <p><span class="versionmodified changed">Changed in version 3.8: </span><em>executable</em> parameter accepts a bytes and <a class="reference internal" href="../glossary.html#term-path-like-object"><span class="xref std std-term">path-like object</span></a>

  712. on Windows.</p>

  713. </div>

  714. <div class="versionchanged">

  715. <p><span class="versionmodified changed">Changed in version 3.12: </span>Changed Windows shell search order for <code class="docutils literal notranslate"><span class="pre">shell=True</span></code>. The current

  716. directory and <code class="docutils literal notranslate"><span class="pre">%PATH%</span></code> are replaced with <code class="docutils literal notranslate"><span class="pre">%COMSPEC%</span></code> and

  717. <code class="docutils literal notranslate"><span class="pre">%SystemRoot%\System32\cmd.exe</span></code>. As a result, dropping a

  718. malicious program named <code class="docutils literal notranslate"><span class="pre">cmd.exe</span></code> into a current directory no

  719. longer works.</p>

  720. </div>

  721. <p><em>stdin</em>, <em>stdout</em> and <em>stderr</em> specify the executed program’s standard input,

  722. standard output and standard error file handles, respectively.  Valid values

  723. are <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>, <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

  724. positive integer), and an existing <a class="reference internal" href="../glossary.html#term-file-object"><span class="xref std std-term">file object</span></a> with a valid file

  725. descriptor.  With the default settings of <code class="docutils literal notranslate"><span class="pre">None</span></code>, no redirection will

  726. occur.  <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

  727. 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>

  728. will be used.  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

  729. that the stderr data from the applications should be captured into the same

  730. file handle as for <em>stdout</em>.</p>

  731. <p>If <em>preexec_fn</em> is set to a callable object, this object will be called in the

  732. child process just before the child is executed.

  733. (POSIX only)</p>

  734. <div class="admonition warning">

  735. <p class="admonition-title">Warning</p>

  736. <p>The <em>preexec_fn</em> parameter is NOT SAFE to use in the presence of threads

  737. in your application.  The child process could deadlock before exec is

  738. called.</p>

  739. </div>

  740. <div class="admonition note">

  741. <p class="admonition-title">Note</p>

  742. <p>If you need to modify the environment for the child use the <em>env</em>

  743. parameter rather than doing it in a <em>preexec_fn</em>.

  744. The <em>start_new_session</em> and <em>process_group</em> parameters should take the place of

  745. code using <em>preexec_fn</em> to call <a class="reference internal" href="os.html#os.setsid" title="os.setsid"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.setsid()</span></code></a> or <a class="reference internal" href="os.html#os.setpgid" title="os.setpgid"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.setpgid()</span></code></a> in the child.</p>

  746. </div>

  747. <div class="versionchanged">

  748. <p><span class="versionmodified changed">Changed in version 3.8: </span>The <em>preexec_fn</em> parameter is no longer supported in subinterpreters.

  749. The use of the parameter in a subinterpreter raises

  750. <a class="reference internal" href="exceptions.html#RuntimeError" title="RuntimeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">RuntimeError</span></code></a>. The new restriction may affect applications that

  751. are deployed in mod_wsgi, uWSGI, and other embedded environments.</p>

  752. </div>

  753. <p>If <em>close_fds</em> is true, all file descriptors except <code class="docutils literal notranslate"><span class="pre">0</span></code>, <code class="docutils literal notranslate"><span class="pre">1</span></code> and

  754. <code class="docutils literal notranslate"><span class="pre">2</span></code> will be closed before the child process is executed.  Otherwise

  755. when <em>close_fds</em> is false, file descriptors obey their inheritable flag

  756. as described in <a class="reference internal" href="os.html#fd-inheritance"><span class="std std-ref">Inheritance of File Descriptors</span></a>.</p>

  757. <p>On Windows, if <em>close_fds</em> is true then no handles will be inherited by the

  758. child process unless explicitly passed in the <code class="docutils literal notranslate"><span class="pre">handle_list</span></code> element of

  759. <a class="reference internal" href="#subprocess.STARTUPINFO.lpAttributeList" title="subprocess.STARTUPINFO.lpAttributeList"><code class="xref py py-attr docutils literal notranslate"><span class="pre">STARTUPINFO.lpAttributeList</span></code></a>, or by standard handle redirection.</p>

  760. <div class="versionchanged">

  761. <p><span class="versionmodified changed">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

  762. what is described above.</p>

  763. </div>

  764. <div class="versionchanged">

  765. <p><span class="versionmodified changed">Changed in version 3.7: </span>On Windows 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

  766. <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> when redirecting the standard handles. It’s now possible to

  767. set <em>close_fds</em> to <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> when redirecting the standard handles.</p>

  768. </div>

  769. <p><em>pass_fds</em> is an optional sequence of file descriptors to keep open

  770. between the parent and child.  Providing any <em>pass_fds</em> forces

  771. <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>

  772. <div class="versionchanged">

  773. <p><span class="versionmodified changed">Changed in version 3.2: </span>The <em>pass_fds</em> parameter was added.</p>

  774. </div>

  775. <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

  776. <em>cwd</em> before executing the child.  <em>cwd</em> can be a string, bytes or

  777. <a class="reference internal" href="../glossary.html#term-path-like-object"><span class="xref std std-term">path-like</span></a> object.  On POSIX, the function

  778. looks for <em>executable</em> (or for the first item in <em>args</em>) relative to <em>cwd</em>

  779. if the executable path is a relative path.</p>

  780. <div class="versionchanged">

  781. <p><span class="versionmodified changed">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> on POSIX.</p>

  782. </div>

  783. <div class="versionchanged">

  784. <p><span class="versionmodified changed">Changed in version 3.7: </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> on Windows.</p>

  785. </div>

  786. <div class="versionchanged">

  787. <p><span class="versionmodified changed">Changed in version 3.8: </span><em>cwd</em> parameter accepts a bytes object on Windows.</p>

  788. </div>

  789. <p>If <em>restore_signals</em> is true (the default) all signals that Python has set to

  790. SIG_IGN are restored to SIG_DFL in the child process before the exec.

  791. Currently this includes the SIGPIPE, SIGXFZ and SIGXFSZ signals.

  792. (POSIX only)</p>

  793. <div class="versionchanged">

  794. <p><span class="versionmodified changed">Changed in version 3.2: </span><em>restore_signals</em> was added.</p>

  795. </div>

  796. <p>If <em>start_new_session</em> is true the <code class="docutils literal notranslate"><span class="pre">setsid()</span></code> system call will be made in the

  797. child process prior to the execution of the subprocess.</p>

  798. <div class="availability docutils container">

  799. <p><a class="reference internal" href="intro.html#availability"><span class="std std-ref">Availability</span></a>: POSIX</p>

  800. </div>

  801. <div class="versionchanged">

  802. <p><span class="versionmodified changed">Changed in version 3.2: </span><em>start_new_session</em> was added.</p>

  803. </div>

  804. <p>If <em>process_group</em> is a non-negative integer, the <code class="docutils literal notranslate"><span class="pre">setpgid(0,</span> <span class="pre">value)</span></code> system call will

  805. be made in the child process prior to the execution of the subprocess.</p>

  806. <div class="availability docutils container">

  807. <p><a class="reference internal" href="intro.html#availability"><span class="std std-ref">Availability</span></a>: POSIX</p>

  808. </div>

  809. <div class="versionchanged">

  810. <p><span class="versionmodified changed">Changed in version 3.11: </span><em>process_group</em> was added.</p>

  811. </div>

  812. <p>If <em>group</em> is not <code class="docutils literal notranslate"><span class="pre">None</span></code>, the setregid() system call will be made in the

  813. child process prior to the execution of the subprocess. If the provided

  814. value is a string, it will be looked up via <a class="reference internal" href="grp.html#grp.getgrnam" title="grp.getgrnam"><code class="xref py py-func docutils literal notranslate"><span class="pre">grp.getgrnam()</span></code></a> and

  815. the value in <code class="docutils literal notranslate"><span class="pre">gr_gid</span></code> will be used. If the value is an integer, it

  816. will be passed verbatim. (POSIX only)</p>

  817. <div class="availability docutils container">

  818. <p><a class="reference internal" href="intro.html#availability"><span class="std std-ref">Availability</span></a>: POSIX</p>

  819. </div>

  820. <div class="versionadded">

  821. <p><span class="versionmodified added">New in version 3.9.</span></p>

  822. </div>

  823. <p>If <em>extra_groups</em> is not <code class="docutils literal notranslate"><span class="pre">None</span></code>, the setgroups() system call will be

  824. made in the child process prior to the execution of the subprocess.

  825. Strings provided in <em>extra_groups</em> will be looked up via

  826. <a class="reference internal" href="grp.html#grp.getgrnam" title="grp.getgrnam"><code class="xref py py-func docutils literal notranslate"><span class="pre">grp.getgrnam()</span></code></a> and the values in <code class="docutils literal notranslate"><span class="pre">gr_gid</span></code> will be used.

  827. Integer values will be passed verbatim. (POSIX only)</p>

  828. <div class="availability docutils container">

  829. <p><a class="reference internal" href="intro.html#availability"><span class="std std-ref">Availability</span></a>: POSIX</p>

  830. </div>

  831. <div class="versionadded">

  832. <p><span class="versionmodified added">New in version 3.9.</span></p>

  833. </div>

  834. <p>If <em>user</em> is not <code class="docutils literal notranslate"><span class="pre">None</span></code>, the setreuid() system call will be made in the

  835. child process prior to the execution of the subprocess. If the provided

  836. value is a string, it will be looked up via <a class="reference internal" href="pwd.html#pwd.getpwnam" title="pwd.getpwnam"><code class="xref py py-func docutils literal notranslate"><span class="pre">pwd.getpwnam()</span></code></a> and

  837. the value in <code class="docutils literal notranslate"><span class="pre">pw_uid</span></code> will be used. If the value is an integer, it will

  838. be passed verbatim. (POSIX only)</p>

  839. <div class="availability docutils container">

  840. <p><a class="reference internal" href="intro.html#availability"><span class="std std-ref">Availability</span></a>: POSIX</p>

  841. </div>

  842. <div class="versionadded">

  843. <p><span class="versionmodified added">New in version 3.9.</span></p>

  844. </div>

  845. <p>If <em>umask</em> is not negative, the umask() system call will be made in the

  846. child process prior to the execution of the subprocess.</p>

  847. <div class="availability docutils container">

  848. <p><a class="reference internal" href="intro.html#availability"><span class="std std-ref">Availability</span></a>: POSIX</p>

  849. </div>

  850. <div class="versionadded">

  851. <p><span class="versionmodified added">New in version 3.9.</span></p>

  852. </div>

  853. <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

  854. variables for the new process; these are used instead of the default

  855. behavior of inheriting the current process’ environment. This mapping can be

  856. str to str on any platform or bytes to bytes on POSIX platforms much like

  857. <a class="reference internal" href="os.html#os.environ" title="os.environ"><code class="xref py py-data docutils literal notranslate"><span class="pre">os.environ</span></code></a> or <a class="reference internal" href="os.html#os.environb" title="os.environb"><code class="xref py py-data docutils literal notranslate"><span class="pre">os.environb</span></code></a>.</p>

  858. <div class="admonition note">

  859. <p class="admonition-title">Note</p>

  860. <p>If specified, <em>env</em> must provide any variables required for the program to

  861. 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

  862. specified <em>env</em> <strong>must</strong> include a valid <span class="target" id="index-4"></span><code class="xref std std-envvar docutils literal notranslate"><span class="pre">SystemRoot</span></code>.</p>

  863. </div>

  864. <p>If <em>encoding</em> or <em>errors</em> are specified, or <em>text</em> is true, the file objects

  865. <em>stdin</em>, <em>stdout</em> and <em>stderr</em> are opened in text mode with the specified

  866. <em>encoding</em> 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>.

  867. The <em>universal_newlines</em> argument is equivalent  to <em>text</em> and is provided

  868. for backwards compatibility. By default, file objects are opened in binary mode.</p>

  869. <div class="versionadded">

  870. <p><span class="versionmodified added">New in version 3.6: </span><em>encoding</em> and <em>errors</em> were added.</p>

  871. </div>

  872. <div class="versionadded">

  873. <p><span class="versionmodified added">New in version 3.7: </span><em>text</em> was added as a more readable alias for <em>universal_newlines</em>.</p>

  874. </div>

  875. <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

  876. passed to the underlying <code class="docutils literal notranslate"><span class="pre">CreateProcess</span></code> function.</p>

  877. <p>If given, <em>creationflags</em>, can be one or more of the following flags:</p>

  878. <ul class="simple">

  879. <li><p><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></p></li>

  880. <li><p><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></p></li>

  881. <li><p><a class="reference internal" href="#subprocess.ABOVE_NORMAL_PRIORITY_CLASS" title="subprocess.ABOVE_NORMAL_PRIORITY_CLASS"><code class="xref py py-data docutils literal notranslate"><span class="pre">ABOVE_NORMAL_PRIORITY_CLASS</span></code></a></p></li>

  882. <li><p><a class="reference internal" href="#subprocess.BELOW_NORMAL_PRIORITY_CLASS" title="subprocess.BELOW_NORMAL_PRIORITY_CLASS"><code class="xref py py-data docutils literal notranslate"><span class="pre">BELOW_NORMAL_PRIORITY_CLASS</span></code></a></p></li>

  883. <li><p><a class="reference internal" href="#subprocess.HIGH_PRIORITY_CLASS" title="subprocess.HIGH_PRIORITY_CLASS"><code class="xref py py-data docutils literal notranslate"><span class="pre">HIGH_PRIORITY_CLASS</span></code></a></p></li>

  884. <li><p><a class="reference internal" href="#subprocess.IDLE_PRIORITY_CLASS" title="subprocess.IDLE_PRIORITY_CLASS"><code class="xref py py-data docutils literal notranslate"><span class="pre">IDLE_PRIORITY_CLASS</span></code></a></p></li>

  885. <li><p><a class="reference internal" href="#subprocess.NORMAL_PRIORITY_CLASS" title="subprocess.NORMAL_PRIORITY_CLASS"><code class="xref py py-data docutils literal notranslate"><span class="pre">NORMAL_PRIORITY_CLASS</span></code></a></p></li>

  886. <li><p><a class="reference internal" href="#subprocess.REALTIME_PRIORITY_CLASS" title="subprocess.REALTIME_PRIORITY_CLASS"><code class="xref py py-data docutils literal notranslate"><span class="pre">REALTIME_PRIORITY_CLASS</span></code></a></p></li>

  887. <li><p><a class="reference internal" href="#subprocess.CREATE_NO_WINDOW" title="subprocess.CREATE_NO_WINDOW"><code class="xref py py-data docutils literal notranslate"><span class="pre">CREATE_NO_WINDOW</span></code></a></p></li>

  888. <li><p><a class="reference internal" href="#subprocess.DETACHED_PROCESS" title="subprocess.DETACHED_PROCESS"><code class="xref py py-data docutils literal notranslate"><span class="pre">DETACHED_PROCESS</span></code></a></p></li>

  889. <li><p><a class="reference internal" href="#subprocess.CREATE_DEFAULT_ERROR_MODE" title="subprocess.CREATE_DEFAULT_ERROR_MODE"><code class="xref py py-data docutils literal notranslate"><span class="pre">CREATE_DEFAULT_ERROR_MODE</span></code></a></p></li>

  890. <li><p><a class="reference internal" href="#subprocess.CREATE_BREAKAWAY_FROM_JOB" title="subprocess.CREATE_BREAKAWAY_FROM_JOB"><code class="xref py py-data docutils literal notranslate"><span class="pre">CREATE_BREAKAWAY_FROM_JOB</span></code></a></p></li>

  891. </ul>

  892. <p><em>pipesize</em> can be used to change the size of the pipe when

  893. <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> is used for <em>stdin</em>, <em>stdout</em> or <em>stderr</em>. The size of the pipe

  894. is only changed on platforms that support this (only Linux at this time of

  895. writing). Other platforms will ignore this parameter.</p>

  896. <div class="versionchanged">

  897. <p><span class="versionmodified changed">Changed in version 3.10: </span>Added the <em>pipesize</em> parameter.</p>

  898. </div>

  899. <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:

  900. on exit, standard file descriptors are closed, and the process is waited for.</p>

  901. <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">&quot;ifconfig&quot;</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>

  902.     <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>

  903. </pre></div>

  904. </div>

  905. <p class="audit-hook"><p>Popen and the other functions in this module that use it raise an

  906. <a class="reference internal" href="sys.html#auditing"><span class="std std-ref">auditing event</span></a> <code class="docutils literal notranslate"><span class="pre">subprocess.Popen</span></code> with arguments

  907. <code class="docutils literal notranslate"><span class="pre">executable</span></code>, <code class="docutils literal notranslate"><span class="pre">args</span></code>, <code class="docutils literal notranslate"><span class="pre">cwd</span></code>, and <code class="docutils literal notranslate"><span class="pre">env</span></code>. The value for <code class="docutils literal notranslate"><span class="pre">args</span></code>

  908. may be a single string or a list of strings, depending on platform.</p>

  909. </p>

  910. <div class="versionchanged">

  911. <p><span class="versionmodified changed">Changed in version 3.2: </span>Added context manager support.</p>

  912. </div>

  913. <div class="versionchanged">

  914. <p><span class="versionmodified changed">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

  915. process is still running.</p>

  916. </div>

  917. <div class="versionchanged">

  918. <p><span class="versionmodified changed">Changed in version 3.8: </span>Popen can use <a class="reference internal" href="os.html#os.posix_spawn" title="os.posix_spawn"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.posix_spawn()</span></code></a> in some cases for better

  919. performance. On Windows Subsystem for Linux and QEMU User Emulation,

  920. Popen constructor using <a class="reference internal" href="os.html#os.posix_spawn" title="os.posix_spawn"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.posix_spawn()</span></code></a> no longer raise an

  921. exception on errors like missing program, but the child process fails

  922. with a non-zero <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>

  923. </div>

  924. </dd></dl>

  925. 

  926. </section>

  927. <section id="exceptions">

  928. <h3>Exceptions<a class="headerlink" href="#exceptions" title="Link to this heading">¶</a></h3>

  929. <p>Exceptions raised in the child process, before the new program has started to

  930. execute, will be re-raised in the parent.</p>

  931. <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,

  932. when trying to execute a non-existent file.  Applications should prepare for

  933. <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. Note that, when <code class="docutils literal notranslate"><span class="pre">shell=True</span></code>, <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>

  934. will be raised by the child only if the selected shell itself was not found.

  935. To determine if the shell failed to find the requested application, it is

  936. necessary to check the return code or output from the subprocess.</p>

  937. <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

  938. arguments.</p>

  939. <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

  940. <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

  941. code.</p>

  942. <p>All of the functions and methods that accept a <em>timeout</em> parameter, such as

  943. <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> 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

  944. the timeout expires before the process exits.</p>

  945. <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>

  946. <div class="versionadded">

  947. <p><span class="versionmodified added">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>

  948. </div>

  949. </section>

  950. </section>

  951. <section id="security-considerations">

  952. <span id="subprocess-security"></span><h2>Security Considerations<a class="headerlink" href="#security-considerations" title="Link to this heading">¶</a></h2>

  953. <p>Unlike some other popen functions, this implementation will never

  954. implicitly call a system shell.  This means that all characters,

  955. including shell metacharacters, can safely be passed to child processes.

  956. If the shell is invoked explicitly, via <code class="docutils literal notranslate"><span class="pre">shell=True</span></code>, it is the application’s

  957. responsibility to ensure that all whitespace and metacharacters are

  958. quoted appropriately to avoid

  959. <a class="reference external" href="https://en.wikipedia.org/wiki/Shell_injection#Shell_injection">shell injection</a>

  960. vulnerabilities. On <a class="reference internal" href="shlex.html#shlex-quote-warning"><span class="std std-ref">some platforms</span></a>, it is possible

  961. to use <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> for this escaping.</p>

  962. </section>

  963. <section id="popen-objects">

  964. <h2>Popen Objects<a class="headerlink" href="#popen-objects" title="Link to this heading">¶</a></h2>

  965. <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>

  966. <dl class="py method">

  967. <dt class="sig sig-object py" id="subprocess.Popen.poll">

  968. <span class="sig-prename descclassname"><span class="pre">Popen.</span></span><span class="sig-name descname"><span class="pre">poll</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.Popen.poll" title="Link to this definition">¶</a></dt>

  969. <dd><p>Check if child process has terminated.  Set and return

  970. <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>

  971. </dd></dl>

  972. 

  973. <dl class="py method">

  974. <dt class="sig sig-object py" id="subprocess.Popen.wait">

  975. <span class="sig-prename descclassname"><span class="pre">Popen.</span></span><span class="sig-name descname"><span class="pre">wait</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">timeout</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.Popen.wait" title="Link to this definition">¶</a></dt>

  976. <dd><p>Wait for child process to terminate.  Set and return

  977. <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>

  978. <p>If the process does not terminate after <em>timeout</em> seconds, raise a

  979. <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

  980. retry the wait.</p>

  981. <div class="admonition note">

  982. <p class="admonition-title">Note</p>

  983. <p>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>

  984. and the child process generates enough output to a pipe such that

  985. it blocks waiting for the OS pipe buffer to accept more data.

  986. 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>

  987. </div>

  988. <div class="admonition note">

  989. <p class="admonition-title">Note</p>

  990. <p>When the <code class="docutils literal notranslate"><span class="pre">timeout</span></code> parameter is not <code class="docutils literal notranslate"><span class="pre">None</span></code>, then (on POSIX) the

  991. function is implemented using a busy loop (non-blocking call and short

  992. sleeps). Use the <a class="reference internal" href="asyncio.html#module-asyncio" title="asyncio: Asynchronous I/O."><code class="xref py py-mod docutils literal notranslate"><span class="pre">asyncio</span></code></a> module for an asynchronous wait: see

  993. <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>

  994. </div>

  995. <div class="versionchanged">

  996. <p><span class="versionmodified changed">Changed in version 3.3: </span><em>timeout</em> was added.</p>

  997. </div>

  998. </dd></dl>

  999. 

  1000. <dl class="py method">

  1001. <dt class="sig sig-object py" id="subprocess.Popen.communicate">

  1002. <span class="sig-prename descclassname"><span class="pre">Popen.</span></span><span class="sig-name descname"><span class="pre">communicate</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">input</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">timeout</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.Popen.communicate" title="Link to this definition">¶</a></dt>

  1003. <dd><p>Interact with process: Send data to stdin.  Read data from stdout and stderr,

  1004. until end-of-file is reached.  Wait for process to terminate and set the

  1005. <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.  The optional <em>input</em> argument should be

  1006. 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

  1007. to the child.  If streams were opened in text mode, <em>input</em> must be a string.

  1008. Otherwise, it must be bytes.</p>

  1009. <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>.

  1010. The data will be strings if streams were opened in text mode; otherwise,

  1011. bytes.</p>

  1012. <p>Note that if you want to send data to the process’s stdin, you need to create

  1013. the Popen object with <code class="docutils literal notranslate"><span class="pre">stdin=PIPE</span></code>.  Similarly, to get anything other than

  1014. <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

  1015. <code class="docutils literal notranslate"><span class="pre">stderr=PIPE</span></code> too.</p>

  1016. <p>If the process does not terminate after <em>timeout</em> seconds, a

  1017. <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

  1018. retrying communication will not lose any output.</p>

  1019. <p>The child process is not killed if the timeout expires, so in order to

  1020. cleanup properly a well-behaved application should kill the child process and

  1021. finish communication:</p>

  1022. <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>

  1023. <span class="k">try</span><span class="p">:</span>

  1024.     <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>

  1025. <span class="k">except</span> <span class="n">TimeoutExpired</span><span class="p">:</span>

  1026.     <span class="n">proc</span><span class="o">.</span><span class="n">kill</span><span class="p">()</span>

  1027.     <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>

  1028. </pre></div>

  1029. </div>

  1030. <div class="admonition note">

  1031. <p class="admonition-title">Note</p>

  1032. <p>The data read is buffered in memory, so do not use this method if the data

  1033. size is large or unlimited.</p>

  1034. </div>

  1035. <div class="versionchanged">

  1036. <p><span class="versionmodified changed">Changed in version 3.3: </span><em>timeout</em> was added.</p>

  1037. </div>

  1038. </dd></dl>

  1039. 

  1040. <dl class="py method">

  1041. <dt class="sig sig-object py" id="subprocess.Popen.send_signal">

  1042. <span class="sig-prename descclassname"><span class="pre">Popen.</span></span><span class="sig-name descname"><span class="pre">send_signal</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">signal</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.Popen.send_signal" title="Link to this definition">¶</a></dt>

  1043. <dd><p>Sends the signal <em>signal</em> to the child.</p>

  1044. <p>Do nothing if the process completed.</p>

  1045. <div class="admonition note">

  1046. <p class="admonition-title">Note</p>

  1047. <p>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

  1048. CTRL_BREAK_EVENT can be sent to processes started with a <em>creationflags</em>

  1049. parameter which includes <code class="docutils literal notranslate"><span class="pre">CREATE_NEW_PROCESS_GROUP</span></code>.</p>

  1050. </div>

  1051. </dd></dl>

  1052. 

  1053. <dl class="py method">

  1054. <dt class="sig sig-object py" id="subprocess.Popen.terminate">

  1055. <span class="sig-prename descclassname"><span class="pre">Popen.</span></span><span class="sig-name descname"><span class="pre">terminate</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.Popen.terminate" title="Link to this definition">¶</a></dt>

  1056. <dd><p>Stop the child. On POSIX OSs the method sends <a class="reference internal" href="signal.html#signal.SIGTERM" title="signal.SIGTERM"><code class="xref py py-const docutils literal notranslate"><span class="pre">SIGTERM</span></code></a> to the

  1057. child. On Windows the Win32 API function <code class="xref c c-func docutils literal notranslate"><span class="pre">TerminateProcess()</span></code> is called

  1058. to stop the child.</p>

  1059. </dd></dl>

  1060. 

  1061. <dl class="py method">

  1062. <dt class="sig sig-object py" id="subprocess.Popen.kill">

  1063. <span class="sig-prename descclassname"><span class="pre">Popen.</span></span><span class="sig-name descname"><span class="pre">kill</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.Popen.kill" title="Link to this definition">¶</a></dt>

  1064. <dd><p>Kills the child. On POSIX OSs the function sends SIGKILL to the child.

  1065. 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>

  1066. </dd></dl>

  1067. 

  1068. <p>The following attributes are also set by the class for you to access.

  1069. Reassigning them to new values is unsupported:</p>

  1070. <dl class="py attribute">

  1071. <dt class="sig sig-object py" id="subprocess.Popen.args">

  1072. <span class="sig-prename descclassname"><span class="pre">Popen.</span></span><span class="sig-name descname"><span class="pre">args</span></span><a class="headerlink" href="#subprocess.Popen.args" title="Link to this definition">¶</a></dt>

  1073. <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

  1074. sequence of program arguments or else a single string.</p>

  1075. <div class="versionadded">

  1076. <p><span class="versionmodified added">New in version 3.3.</span></p>

  1077. </div>

  1078. </dd></dl>

  1079. 

  1080. <dl class="py attribute">

  1081. <dt class="sig sig-object py" id="subprocess.Popen.stdin">

  1082. <span class="sig-prename descclassname"><span class="pre">Popen.</span></span><span class="sig-name descname"><span class="pre">stdin</span></span><a class="headerlink" href="#subprocess.Popen.stdin" title="Link to this definition">¶</a></dt>

  1083. <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

  1084. 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>

  1085. arguments were specified or the <em>text</em> or <em>universal_newlines</em> argument

  1086. was <code class="docutils literal notranslate"><span class="pre">True</span></code>, the stream is a text stream, otherwise it is a byte stream.

  1087. 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>

  1088. </dd></dl>

  1089. 

  1090. <dl class="py attribute">

  1091. <dt class="sig sig-object py" id="subprocess.Popen.stdout">

  1092. <span class="sig-prename descclassname"><span class="pre">Popen.</span></span><span class="sig-name descname"><span class="pre">stdout</span></span><a class="headerlink" href="#subprocess.Popen.stdout" title="Link to this definition">¶</a></dt>

  1093. <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

  1094. 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

  1095. output from the child process. If the <em>encoding</em> or <em>errors</em> arguments were

  1096. specified or the <em>text</em> or <em>universal_newlines</em> argument was <code class="docutils literal notranslate"><span class="pre">True</span></code>, the

  1097. stream is a text stream, otherwise it is a byte stream. If the <em>stdout</em>

  1098. 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>

  1099. </dd></dl>

  1100. 

  1101. <dl class="py attribute">

  1102. <dt class="sig sig-object py" id="subprocess.Popen.stderr">

  1103. <span class="sig-prename descclassname"><span class="pre">Popen.</span></span><span class="sig-name descname"><span class="pre">stderr</span></span><a class="headerlink" href="#subprocess.Popen.stderr" title="Link to this definition">¶</a></dt>

  1104. <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

  1105. 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

  1106. error output from the child process. If the <em>encoding</em> or <em>errors</em> arguments

  1107. were specified or the <em>text</em> or <em>universal_newlines</em> argument was <code class="docutils literal notranslate"><span class="pre">True</span></code>, the

  1108. stream is a text stream, otherwise it is a byte stream. If the <em>stderr</em> argument

  1109. 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>

  1110. </dd></dl>

  1111. 

  1112. <div class="admonition warning">

  1113. <p class="admonition-title">Warning</p>

  1114. <p>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>,

  1115. <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

  1116. deadlocks due to any of the other OS pipe buffers filling up and blocking the

  1117. child process.</p>

  1118. </div>

  1119. <dl class="py attribute">

  1120. <dt class="sig sig-object py" id="subprocess.Popen.pid">

  1121. <span class="sig-prename descclassname"><span class="pre">Popen.</span></span><span class="sig-name descname"><span class="pre">pid</span></span><a class="headerlink" href="#subprocess.Popen.pid" title="Link to this definition">¶</a></dt>

  1122. <dd><p>The process ID of the child process.</p>

  1123. <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

  1124. of the spawned shell.</p>

  1125. </dd></dl>

  1126. 

  1127. <dl class="py attribute">

  1128. <dt class="sig sig-object py" id="subprocess.Popen.returncode">

  1129. <span class="sig-prename descclassname"><span class="pre">Popen.</span></span><span class="sig-name descname"><span class="pre">returncode</span></span><a class="headerlink" href="#subprocess.Popen.returncode" title="Link to this definition">¶</a></dt>

  1130. <dd><p>The child return code. Initially <code class="docutils literal notranslate"><span class="pre">None</span></code>, <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> is set by

  1131. a call to the <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>, <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>, or <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> methods

  1132. if they detect that the process has terminated.</p>

  1133. <p>A <code class="docutils literal notranslate"><span class="pre">None</span></code> value indicates that the process hadn’t yet terminated at the

  1134. time of the last method call.</p>

  1135. <p>A negative value <code class="docutils literal notranslate"><span class="pre">-N</span></code> indicates that the child was terminated by signal

  1136. <code class="docutils literal notranslate"><span class="pre">N</span></code> (POSIX only).</p>

  1137. </dd></dl>

  1138. 

  1139. </section>

  1140. <section id="windows-popen-helpers">

  1141. <h2>Windows Popen Helpers<a class="headerlink" href="#windows-popen-helpers" title="Link to this heading">¶</a></h2>

  1142. <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

  1143. on Windows.</p>

  1144. <dl class="py class">

  1145. <dt class="sig sig-object py" id="subprocess.STARTUPINFO">

  1146. <em class="property"><span class="pre">class</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">STARTUPINFO</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="o"><span class="pre">*</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">dwFlags</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">0</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">hStdInput</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">hStdOutput</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">hStdError</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">wShowWindow</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">0</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">lpAttributeList</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.STARTUPINFO" title="Link to this definition">¶</a></dt>

  1147. <dd><p>Partial support of the Windows

  1148. <a class="reference external" href="https://msdn.microsoft.com/en-us/library/ms686331(v=vs.85).aspx">STARTUPINFO</a>

  1149. 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.  The following attributes can

  1150. be set by passing them as keyword-only arguments.</p>

  1151. <div class="versionchanged">

  1152. <p><span class="versionmodified changed">Changed in version 3.7: </span>Keyword-only argument support was added.</p>

  1153. </div>

  1154. <dl class="py attribute">

  1155. <dt class="sig sig-object py" id="subprocess.STARTUPINFO.dwFlags">

  1156. <span class="sig-name descname"><span class="pre">dwFlags</span></span><a class="headerlink" href="#subprocess.STARTUPINFO.dwFlags" title="Link to this definition">¶</a></dt>

  1157. <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>

  1158. attributes are used when the process creates a window.</p>

  1159. <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>

  1160. <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>

  1161. </pre></div>

  1162. </div>

  1163. </dd></dl>

  1164. 

  1165. <dl class="py attribute">

  1166. <dt class="sig sig-object py" id="subprocess.STARTUPINFO.hStdInput">

  1167. <span class="sig-name descname"><span class="pre">hStdInput</span></span><a class="headerlink" href="#subprocess.STARTUPINFO.hStdInput" title="Link to this definition">¶</a></dt>

  1168. <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

  1169. is the standard input handle for the process. If

  1170. <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

  1171. input is the keyboard buffer.</p>

  1172. </dd></dl>

  1173. 

  1174. <dl class="py attribute">

  1175. <dt class="sig sig-object py" id="subprocess.STARTUPINFO.hStdOutput">

  1176. <span class="sig-name descname"><span class="pre">hStdOutput</span></span><a class="headerlink" href="#subprocess.STARTUPINFO.hStdOutput" title="Link to this definition">¶</a></dt>

  1177. <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

  1178. is the standard output handle for the process. Otherwise, this attribute

  1179. is ignored and the default for standard output is the console window’s

  1180. buffer.</p>

  1181. </dd></dl>

  1182. 

  1183. <dl class="py attribute">

  1184. <dt class="sig sig-object py" id="subprocess.STARTUPINFO.hStdError">

  1185. <span class="sig-name descname"><span class="pre">hStdError</span></span><a class="headerlink" href="#subprocess.STARTUPINFO.hStdError" title="Link to this definition">¶</a></dt>

  1186. <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

  1187. is the standard error handle for the process. Otherwise, this attribute is

  1188. ignored and the default for standard error is the console window’s buffer.</p>

  1189. </dd></dl>

  1190. 

  1191. <dl class="py attribute">

  1192. <dt class="sig sig-object py" id="subprocess.STARTUPINFO.wShowWindow">

  1193. <span class="sig-name descname"><span class="pre">wShowWindow</span></span><a class="headerlink" href="#subprocess.STARTUPINFO.wShowWindow" title="Link to this definition">¶</a></dt>

  1194. <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

  1195. can be any of the values that can be specified in the <code class="docutils literal notranslate"><span class="pre">nCmdShow</span></code>

  1196. parameter for the

  1197. <a class="reference external" href="https://msdn.microsoft.com/en-us/library/ms633548(v=vs.85).aspx">ShowWindow</a>

  1198. function, except for <code class="docutils literal notranslate"><span class="pre">SW_SHOWDEFAULT</span></code>. Otherwise, this attribute is

  1199. ignored.</p>

  1200. <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

  1201. <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>

  1202. </dd></dl>

  1203. 

  1204. <dl class="py attribute">

  1205. <dt class="sig sig-object py" id="subprocess.STARTUPINFO.lpAttributeList">

  1206. <span class="sig-name descname"><span class="pre">lpAttributeList</span></span><a class="headerlink" href="#subprocess.STARTUPINFO.lpAttributeList" title="Link to this definition">¶</a></dt>

  1207. <dd><p>A dictionary of additional attributes for process creation as given in

  1208. <code class="docutils literal notranslate"><span class="pre">STARTUPINFOEX</span></code>, see

  1209. <a class="reference external" href="https://msdn.microsoft.com/en-us/library/windows/desktop/ms686880(v=vs.85).aspx">UpdateProcThreadAttribute</a>.</p>

  1210. <p>Supported attributes:</p>

  1211. <dl>

  1212. <dt><strong>handle_list</strong></dt><dd><p>Sequence of handles that will be inherited. <em>close_fds</em> must be true if

  1213. non-empty.</p>

  1214. <p>The handles must be temporarily made inheritable by

  1215. <a class="reference internal" href="os.html#os.set_handle_inheritable" title="os.set_handle_inheritable"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.set_handle_inheritable()</span></code></a> when passed to 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>

  1216. constructor, else <a class="reference internal" href="exceptions.html#OSError" title="OSError"><code class="xref py py-class docutils literal notranslate"><span class="pre">OSError</span></code></a> will be raised with Windows error

  1217. <code class="docutils literal notranslate"><span class="pre">ERROR_INVALID_PARAMETER</span></code> (87).</p>

  1218. <div class="admonition warning">

  1219. <p class="admonition-title">Warning</p>

  1220. <p>In a multithreaded process, use caution to avoid leaking handles

  1221. that are marked inheritable when combining this feature with

  1222. concurrent calls to other process creation functions that inherit

  1223. all handles such as <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>.  This also applies to

  1224. standard handle redirection, which temporarily creates inheritable

  1225. handles.</p>

  1226. </div>

  1227. </dd>

  1228. </dl>

  1229. <div class="versionadded">

  1230. <p><span class="versionmodified added">New in version 3.7.</span></p>

  1231. </div>

  1232. </dd></dl>

  1233. 

  1234. </dd></dl>

  1235. 

  1236. <section id="windows-constants">

  1237. <h3>Windows Constants<a class="headerlink" href="#windows-constants" title="Link to this heading">¶</a></h3>

  1238. <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>

  1239. <dl class="py data">

  1240. <dt class="sig sig-object py" id="subprocess.STD_INPUT_HANDLE">

  1241. <span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">STD_INPUT_HANDLE</span></span><a class="headerlink" href="#subprocess.STD_INPUT_HANDLE" title="Link to this definition">¶</a></dt>

  1242. <dd><p>The standard input device. Initially, this is the console input buffer,

  1243. <code class="docutils literal notranslate"><span class="pre">CONIN$</span></code>.</p>

  1244. </dd></dl>

  1245. 

  1246. <dl class="py data">

  1247. <dt class="sig sig-object py" id="subprocess.STD_OUTPUT_HANDLE">

  1248. <span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">STD_OUTPUT_HANDLE</span></span><a class="headerlink" href="#subprocess.STD_OUTPUT_HANDLE" title="Link to this definition">¶</a></dt>

  1249. <dd><p>The standard output device. Initially, this is the active console screen

  1250. buffer, <code class="docutils literal notranslate"><span class="pre">CONOUT$</span></code>.</p>

  1251. </dd></dl>

  1252. 

  1253. <dl class="py data">

  1254. <dt class="sig sig-object py" id="subprocess.STD_ERROR_HANDLE">

  1255. <span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">STD_ERROR_HANDLE</span></span><a class="headerlink" href="#subprocess.STD_ERROR_HANDLE" title="Link to this definition">¶</a></dt>

  1256. <dd><p>The standard error device. Initially, this is the active console screen

  1257. buffer, <code class="docutils literal notranslate"><span class="pre">CONOUT$</span></code>.</p>

  1258. </dd></dl>

  1259. 

  1260. <dl class="py data">

  1261. <dt class="sig sig-object py" id="subprocess.SW_HIDE">

  1262. <span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">SW_HIDE</span></span><a class="headerlink" href="#subprocess.SW_HIDE" title="Link to this definition">¶</a></dt>

  1263. <dd><p>Hides the window. Another window will be activated.</p>

  1264. </dd></dl>

  1265. 

  1266. <dl class="py data">

  1267. <dt class="sig sig-object py" id="subprocess.STARTF_USESTDHANDLES">

  1268. <span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">STARTF_USESTDHANDLES</span></span><a class="headerlink" href="#subprocess.STARTF_USESTDHANDLES" title="Link to this definition">¶</a></dt>

  1269. <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>,

  1270. <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

  1271. contain additional information.</p>

  1272. </dd></dl>

  1273. 

  1274. <dl class="py data">

  1275. <dt class="sig sig-object py" id="subprocess.STARTF_USESHOWWINDOW">

  1276. <span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">STARTF_USESHOWWINDOW</span></span><a class="headerlink" href="#subprocess.STARTF_USESHOWWINDOW" title="Link to this definition">¶</a></dt>

  1277. <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

  1278. additional information.</p>

  1279. </dd></dl>

  1280. 

  1281. <dl class="py data">

  1282. <dt class="sig sig-object py" id="subprocess.CREATE_NEW_CONSOLE">

  1283. <span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">CREATE_NEW_CONSOLE</span></span><a class="headerlink" href="#subprocess.CREATE_NEW_CONSOLE" title="Link to this definition">¶</a></dt>

  1284. <dd><p>The new process has a new console, instead of inheriting its parent’s

  1285. console (the default).</p>

  1286. </dd></dl>

  1287. 

  1288. <dl class="py data">

  1289. <dt class="sig sig-object py" id="subprocess.CREATE_NEW_PROCESS_GROUP">

  1290. <span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">CREATE_NEW_PROCESS_GROUP</span></span><a class="headerlink" href="#subprocess.CREATE_NEW_PROCESS_GROUP" title="Link to this definition">¶</a></dt>

  1291. <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

  1292. 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>

  1293. on the subprocess.</p>

  1294. <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>

  1295. </dd></dl>

  1296. 

  1297. <dl class="py data">

  1298. <dt class="sig sig-object py" id="subprocess.ABOVE_NORMAL_PRIORITY_CLASS">

  1299. <span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">ABOVE_NORMAL_PRIORITY_CLASS</span></span><a class="headerlink" href="#subprocess.ABOVE_NORMAL_PRIORITY_CLASS" title="Link to this definition">¶</a></dt>

  1300. <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

  1301. will have an above average priority.</p>

  1302. <div class="versionadded">

  1303. <p><span class="versionmodified added">New in version 3.7.</span></p>

  1304. </div>

  1305. </dd></dl>

  1306. 

  1307. <dl class="py data">

  1308. <dt class="sig sig-object py" id="subprocess.BELOW_NORMAL_PRIORITY_CLASS">

  1309. <span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">BELOW_NORMAL_PRIORITY_CLASS</span></span><a class="headerlink" href="#subprocess.BELOW_NORMAL_PRIORITY_CLASS" title="Link to this definition">¶</a></dt>

  1310. <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

  1311. will have a below average priority.</p>

  1312. <div class="versionadded">

  1313. <p><span class="versionmodified added">New in version 3.7.</span></p>

  1314. </div>

  1315. </dd></dl>

  1316. 

  1317. <dl class="py data">

  1318. <dt class="sig sig-object py" id="subprocess.HIGH_PRIORITY_CLASS">

  1319. <span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">HIGH_PRIORITY_CLASS</span></span><a class="headerlink" href="#subprocess.HIGH_PRIORITY_CLASS" title="Link to this definition">¶</a></dt>

  1320. <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

  1321. will have a high priority.</p>

  1322. <div class="versionadded">

  1323. <p><span class="versionmodified added">New in version 3.7.</span></p>

  1324. </div>

  1325. </dd></dl>

  1326. 

  1327. <dl class="py data">

  1328. <dt class="sig sig-object py" id="subprocess.IDLE_PRIORITY_CLASS">

  1329. <span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">IDLE_PRIORITY_CLASS</span></span><a class="headerlink" href="#subprocess.IDLE_PRIORITY_CLASS" title="Link to this definition">¶</a></dt>

  1330. <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

  1331. will have an idle (lowest) priority.</p>

  1332. <div class="versionadded">

  1333. <p><span class="versionmodified added">New in version 3.7.</span></p>

  1334. </div>

  1335. </dd></dl>

  1336. 

  1337. <dl class="py data">

  1338. <dt class="sig sig-object py" id="subprocess.NORMAL_PRIORITY_CLASS">

  1339. <span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">NORMAL_PRIORITY_CLASS</span></span><a class="headerlink" href="#subprocess.NORMAL_PRIORITY_CLASS" title="Link to this definition">¶</a></dt>

  1340. <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

  1341. will have an normal priority. (default)</p>

  1342. <div class="versionadded">

  1343. <p><span class="versionmodified added">New in version 3.7.</span></p>

  1344. </div>

  1345. </dd></dl>

  1346. 

  1347. <dl class="py data">

  1348. <dt class="sig sig-object py" id="subprocess.REALTIME_PRIORITY_CLASS">

  1349. <span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">REALTIME_PRIORITY_CLASS</span></span><a class="headerlink" href="#subprocess.REALTIME_PRIORITY_CLASS" title="Link to this definition">¶</a></dt>

  1350. <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

  1351. will have realtime priority.

  1352. You should almost never use REALTIME_PRIORITY_CLASS, because this interrupts

  1353. system threads that manage mouse input, keyboard input, and background disk

  1354. flushing. This class can be appropriate for applications that “talk” directly

  1355. to hardware or that perform brief tasks that should have limited interruptions.</p>

  1356. <div class="versionadded">

  1357. <p><span class="versionmodified added">New in version 3.7.</span></p>

  1358. </div>

  1359. </dd></dl>

  1360. 

  1361. <dl class="py data">

  1362. <dt class="sig sig-object py" id="subprocess.CREATE_NO_WINDOW">

  1363. <span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">CREATE_NO_WINDOW</span></span><a class="headerlink" href="#subprocess.CREATE_NO_WINDOW" title="Link to this definition">¶</a></dt>

  1364. <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

  1365. will not create a window.</p>

  1366. <div class="versionadded">

  1367. <p><span class="versionmodified added">New in version 3.7.</span></p>

  1368. </div>

  1369. </dd></dl>

  1370. 

  1371. <dl class="py data">

  1372. <dt class="sig sig-object py" id="subprocess.DETACHED_PROCESS">

  1373. <span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">DETACHED_PROCESS</span></span><a class="headerlink" href="#subprocess.DETACHED_PROCESS" title="Link to this definition">¶</a></dt>

  1374. <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

  1375. will not inherit its parent’s console.

  1376. This value cannot be used with CREATE_NEW_CONSOLE.</p>

  1377. <div class="versionadded">

  1378. <p><span class="versionmodified added">New in version 3.7.</span></p>

  1379. </div>

  1380. </dd></dl>

  1381. 

  1382. <dl class="py data">

  1383. <dt class="sig sig-object py" id="subprocess.CREATE_DEFAULT_ERROR_MODE">

  1384. <span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">CREATE_DEFAULT_ERROR_MODE</span></span><a class="headerlink" href="#subprocess.CREATE_DEFAULT_ERROR_MODE" title="Link to this definition">¶</a></dt>

  1385. <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

  1386. does not inherit the error mode of the calling process. Instead, the new

  1387. process gets the default error mode.

  1388. This feature is particularly useful for multithreaded shell applications

  1389. that run with hard errors disabled.</p>

  1390. <div class="versionadded">

  1391. <p><span class="versionmodified added">New in version 3.7.</span></p>

  1392. </div>

  1393. </dd></dl>

  1394. 

  1395. <dl class="py data">

  1396. <dt class="sig sig-object py" id="subprocess.CREATE_BREAKAWAY_FROM_JOB">

  1397. <span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">CREATE_BREAKAWAY_FROM_JOB</span></span><a class="headerlink" href="#subprocess.CREATE_BREAKAWAY_FROM_JOB" title="Link to this definition">¶</a></dt>

  1398. <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

  1399. is not associated with the job.</p>

  1400. <div class="versionadded">

  1401. <p><span class="versionmodified added">New in version 3.7.</span></p>

  1402. </div>

  1403. </dd></dl>

  1404. 

  1405. </section>

  1406. </section>

  1407. <section id="older-high-level-api">

  1408. <span id="call-function-trio"></span><h2>Older high-level API<a class="headerlink" href="#older-high-level-api" title="Link to this heading">¶</a></h2>

  1409. <p>Prior to Python 3.5, these three functions comprised the high level API to

  1410. 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

  1411. calls these functions.</p>

  1412. <dl class="py function">

  1413. <dt class="sig sig-object py" id="subprocess.call">

  1414. <span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">call</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">args</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">*</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">stdin</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">stdout</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">stderr</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">shell</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">False</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">cwd</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">timeout</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">**</span></span><span class="n"><span class="pre">other_popen_kwargs</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.call" title="Link to this definition">¶</a></dt>

  1415. <dd><p>Run the command described by <em>args</em>.  Wait for command to complete, then

  1416. 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>

  1417. <p>Code needing to capture stdout or stderr should 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> instead:</p>

  1418. <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>

  1419. </pre></div>

  1420. </div>

  1421. <p>To suppress stdout or stderr, supply a value of <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>.</p>

  1422. <p>The arguments shown above are merely some common ones.

  1423. The full function signature is the

  1424. 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

  1425. supplied arguments other than <em>timeout</em> directly through to that interface.</p>

  1426. <div class="admonition note">

  1427. <p class="admonition-title">Note</p>

  1428. <p>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

  1429. function.  The child process will block if it generates enough

  1430. output to a pipe to fill up the OS pipe buffer as the pipes are

  1431. not being read from.</p>

  1432. </div>

  1433. <div class="versionchanged">

  1434. <p><span class="versionmodified changed">Changed in version 3.3: </span><em>timeout</em> was added.</p>

  1435. </div>

  1436. <div class="versionchanged">

  1437. <p><span class="versionmodified changed">Changed in version 3.12: </span>Changed Windows shell search order for <code class="docutils literal notranslate"><span class="pre">shell=True</span></code>. The current

  1438. directory and <code class="docutils literal notranslate"><span class="pre">%PATH%</span></code> are replaced with <code class="docutils literal notranslate"><span class="pre">%COMSPEC%</span></code> and

  1439. <code class="docutils literal notranslate"><span class="pre">%SystemRoot%\System32\cmd.exe</span></code>. As a result, dropping a

  1440. malicious program named <code class="docutils literal notranslate"><span class="pre">cmd.exe</span></code> into a current directory no

  1441. longer works.</p>

  1442. </div>

  1443. </dd></dl>

  1444. 

  1445. <dl class="py function">

  1446. <dt class="sig sig-object py" id="subprocess.check_call">

  1447. <span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">check_call</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">args</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">*</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">stdin</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">stdout</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">stderr</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">shell</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">False</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">cwd</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">timeout</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">**</span></span><span class="n"><span class="pre">other_popen_kwargs</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.check_call" title="Link to this definition">¶</a></dt>

  1448. <dd><p>Run command with arguments.  Wait for command to complete. If the return

  1449. 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

  1450. <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

  1451. <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.

  1452. If <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> was unable to start the process it will propagate the exception

  1453. that was raised.</p>

  1454. <p>Code needing to capture stdout or stderr should 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> instead:</p>

  1455. <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>

  1456. </pre></div>

  1457. </div>

  1458. <p>To suppress stdout or stderr, supply a value of <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>.</p>

  1459. <p>The arguments shown above are merely some common ones.

  1460. The full function signature is the

  1461. 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

  1462. supplied arguments other than <em>timeout</em> directly through to that interface.</p>

  1463. <div class="admonition note">

  1464. <p class="admonition-title">Note</p>

  1465. <p>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

  1466. function.  The child process will block if it generates enough

  1467. output to a pipe to fill up the OS pipe buffer as the pipes are

  1468. not being read from.</p>

  1469. </div>

  1470. <div class="versionchanged">

  1471. <p><span class="versionmodified changed">Changed in version 3.3: </span><em>timeout</em> was added.</p>

  1472. </div>

  1473. <div class="versionchanged">

  1474. <p><span class="versionmodified changed">Changed in version 3.12: </span>Changed Windows shell search order for <code class="docutils literal notranslate"><span class="pre">shell=True</span></code>. The current

  1475. directory and <code class="docutils literal notranslate"><span class="pre">%PATH%</span></code> are replaced with <code class="docutils literal notranslate"><span class="pre">%COMSPEC%</span></code> and

  1476. <code class="docutils literal notranslate"><span class="pre">%SystemRoot%\System32\cmd.exe</span></code>. As a result, dropping a

  1477. malicious program named <code class="docutils literal notranslate"><span class="pre">cmd.exe</span></code> into a current directory no

  1478. longer works.</p>

  1479. </div>

  1480. </dd></dl>

  1481. 

  1482. <dl class="py function">

  1483. <dt class="sig sig-object py" id="subprocess.check_output">

  1484. <span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">check_output</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">args</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">*</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">stdin</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">stderr</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">shell</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">False</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">cwd</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">encoding</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">errors</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">universal_newlines</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">timeout</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">text</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">**</span></span><span class="n"><span class="pre">other_popen_kwargs</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.check_output" title="Link to this definition">¶</a></dt>

  1485. <dd><p>Run command with arguments and return its output.</p>

  1486. <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

  1487. <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

  1488. <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

  1489. <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>

  1490. <p>This is equivalent to:</p>

  1491. <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>

  1492. </pre></div>

  1493. </div>

  1494. <p>The arguments shown above are merely some common ones.

  1495. 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> -

  1496. most arguments are passed directly through to that interface.

  1497. One API deviation 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> behavior exists: passing <code class="docutils literal notranslate"><span class="pre">input=None</span></code>

  1498. will behave the same as <code class="docutils literal notranslate"><span class="pre">input=b''</span></code> (or <code class="docutils literal notranslate"><span class="pre">input=''</span></code>, depending on other

  1499. arguments) rather than using the parent’s standard input file handle.</p>

  1500. <p>By default, this function will return the data as encoded bytes. The actual

  1501. encoding of the output data may depend on the command being invoked, so the

  1502. decoding to text will often need to be handled at the application level.</p>

  1503. <p>This behaviour may be overridden by setting <em>text</em>, <em>encoding</em>, <em>errors</em>,

  1504. or <em>universal_newlines</em> to <code class="docutils literal notranslate"><span class="pre">True</span></code> as described in

  1505. <a class="reference internal" href="#frequently-used-arguments"><span class="std std-ref">Frequently Used Arguments</span></a> and <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>.</p>

  1506. <p>To also capture standard error in the result, use

  1507. <code class="docutils literal notranslate"><span class="pre">stderr=subprocess.STDOUT</span></code>:</p>

  1508. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">subprocess</span><span class="o">.</span><span class="n">check_output</span><span class="p">(</span>

  1509. <span class="gp">... </span>    <span class="s2">&quot;ls non_existent_file; exit 0&quot;</span><span class="p">,</span>

  1510. <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>

  1511. <span class="gp">... </span>    <span class="n">shell</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>

  1512. <span class="go">&#39;ls: non_existent_file: No such file or directory\n&#39;</span>

  1513. </pre></div>

  1514. </div>

  1515. <div class="versionadded">

  1516. <p><span class="versionmodified added">New in version 3.1.</span></p>

  1517. </div>

  1518. <div class="versionchanged">

  1519. <p><span class="versionmodified changed">Changed in version 3.3: </span><em>timeout</em> was added.</p>

  1520. </div>

  1521. <div class="versionchanged">

  1522. <p><span class="versionmodified changed">Changed in version 3.4: </span>Support for the <em>input</em> keyword argument was added.</p>

  1523. </div>

  1524. <div class="versionchanged">

  1525. <p><span class="versionmodified changed">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>

  1526. </div>

  1527. <div class="versionadded">

  1528. <p><span class="versionmodified added">New in version 3.7: </span><em>text</em> was added as a more readable alias for <em>universal_newlines</em>.</p>

  1529. </div>

  1530. <div class="versionchanged">

  1531. <p><span class="versionmodified changed">Changed in version 3.12: </span>Changed Windows shell search order for <code class="docutils literal notranslate"><span class="pre">shell=True</span></code>. The current

  1532. directory and <code class="docutils literal notranslate"><span class="pre">%PATH%</span></code> are replaced with <code class="docutils literal notranslate"><span class="pre">%COMSPEC%</span></code> and

  1533. <code class="docutils literal notranslate"><span class="pre">%SystemRoot%\System32\cmd.exe</span></code>. As a result, dropping a

  1534. malicious program named <code class="docutils literal notranslate"><span class="pre">cmd.exe</span></code> into a current directory no

  1535. longer works.</p>

  1536. </div>

  1537. </dd></dl>

  1538. 

  1539. </section>

  1540. <section id="replacing-older-functions-with-the-subprocess-module">

  1541. <span id="subprocess-replacements"></span><h2>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="Link to this heading">¶</a></h2>

  1542. <p>In this section, “a becomes b” means that b can be used as a replacement for a.</p>

  1543. <div class="admonition note">

  1544. <p class="admonition-title">Note</p>

  1545. <p>All “a” functions in this section fail (more or less) silently if the

  1546. 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>

  1547. instead.</p>

  1548. <p>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

  1549. <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

  1550. return code. The output is still available as the

  1551. <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>

  1552. </div>

  1553. <p>In the following examples, we assume that the relevant functions have already

  1554. 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>

  1555. <section id="replacing-bin-sh-shell-command-substitution">

  1556. <h3>Replacing <strong class="program">/bin/sh</strong> shell command substitution<a class="headerlink" href="#replacing-bin-sh-shell-command-substitution" title="Link to this heading">¶</a></h3>

  1557. <div class="highlight-bash notranslate"><div class="highlight"><pre><span></span><span class="nv">output</span><span class="o">=</span><span class="k">$(</span>mycmd<span class="w"> </span>myarg<span class="k">)</span>

  1558. </pre></div>

  1559. </div>

  1560. <p>becomes:</p>

  1561. <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">&quot;mycmd&quot;</span><span class="p">,</span> <span class="s2">&quot;myarg&quot;</span><span class="p">])</span>

  1562. </pre></div>

  1563. </div>

  1564. </section>

  1565. <section id="replacing-shell-pipeline">

  1566. <h3>Replacing shell pipeline<a class="headerlink" href="#replacing-shell-pipeline" title="Link to this heading">¶</a></h3>

  1567. <div class="highlight-bash notranslate"><div class="highlight"><pre><span></span><span class="nv">output</span><span class="o">=</span><span class="k">$(</span>dmesg<span class="w"> </span><span class="p">|</span><span class="w"> </span>grep<span class="w"> </span>hda<span class="k">)</span>

  1568. </pre></div>

  1569. </div>

  1570. <p>becomes:</p>

  1571. <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">&quot;dmesg&quot;</span><span class="p">],</span> <span class="n">stdout</span><span class="o">=</span><span class="n">PIPE</span><span class="p">)</span>

  1572. <span class="n">p2</span> <span class="o">=</span> <span class="n">Popen</span><span class="p">([</span><span class="s2">&quot;grep&quot;</span><span class="p">,</span> <span class="s2">&quot;hda&quot;</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>

  1573. <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>

  1574. <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>

  1575. </pre></div>

  1576. </div>

  1577. <p>The <code class="docutils literal notranslate"><span class="pre">p1.stdout.close()</span></code> call after starting the p2 is important in order for

  1578. p1 to receive a SIGPIPE if p2 exits before p1.</p>

  1579. <p>Alternatively, for trusted input, the shell’s own pipeline support may still

  1580. be used directly:</p>

  1581. <div class="highlight-bash notranslate"><div class="highlight"><pre><span></span><span class="nv">output</span><span class="o">=</span><span class="k">$(</span>dmesg<span class="w"> </span><span class="p">|</span><span class="w"> </span>grep<span class="w"> </span>hda<span class="k">)</span>

  1582. </pre></div>

  1583. </div>

  1584. <p>becomes:</p>

  1585. <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">&quot;dmesg | grep hda&quot;</span><span class="p">,</span> <span class="n">shell</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>

  1586. </pre></div>

  1587. </div>

  1588. </section>

  1589. <section id="replacing-os-system">

  1590. <h3>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="Link to this heading">¶</a></h3>

  1591. <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">&quot;mycmd&quot;</span> <span class="o">+</span> <span class="s2">&quot; myarg&quot;</span><span class="p">)</span>

  1592. <span class="c1"># becomes</span>

  1593. <span class="n">retcode</span> <span class="o">=</span> <span class="n">call</span><span class="p">(</span><span class="s2">&quot;mycmd&quot;</span> <span class="o">+</span> <span class="s2">&quot; myarg&quot;</span><span class="p">,</span> <span class="n">shell</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>

  1594. </pre></div>

  1595. </div>

  1596. <p>Notes:</p>

  1597. <ul class="simple">

  1598. <li><p>Calling the program through the shell is usually not required.</p></li>

  1599. <li><p>The <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> return value is encoded differently to that of

  1600. <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>.</p></li>

  1601. <li><p>The <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> function ignores SIGINT and SIGQUIT signals while

  1602. the command is running, but the caller must do this separately when

  1603. 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.</p></li>

  1604. </ul>

  1605. <p>A more realistic example would look like this:</p>

  1606. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">try</span><span class="p">:</span>

  1607.     <span class="n">retcode</span> <span class="o">=</span> <span class="n">call</span><span class="p">(</span><span class="s2">&quot;mycmd&quot;</span> <span class="o">+</span> <span class="s2">&quot; myarg&quot;</span><span class="p">,</span> <span class="n">shell</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>

  1608.     <span class="k">if</span> <span class="n">retcode</span> <span class="o">&lt;</span> <span class="mi">0</span><span class="p">:</span>

  1609.         <span class="nb">print</span><span class="p">(</span><span class="s2">&quot;Child was terminated by signal&quot;</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>

  1610.     <span class="k">else</span><span class="p">:</span>

  1611.         <span class="nb">print</span><span class="p">(</span><span class="s2">&quot;Child returned&quot;</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>

  1612. <span class="k">except</span> <span class="ne">OSError</span> <span class="k">as</span> <span class="n">e</span><span class="p">:</span>

  1613.     <span class="nb">print</span><span class="p">(</span><span class="s2">&quot;Execution failed:&quot;</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>

  1614. </pre></div>

  1615. </div>

  1616. </section>

  1617. <section id="replacing-the-os-spawn-family">

  1618. <h3>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="Link to this heading">¶</a></h3>

  1619. <p>P_NOWAIT example:</p>

  1620. <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">&quot;/bin/mycmd&quot;</span><span class="p">,</span> <span class="s2">&quot;mycmd&quot;</span><span class="p">,</span> <span class="s2">&quot;myarg&quot;</span><span class="p">)</span>

  1621. <span class="o">==&gt;</span>

  1622. <span class="n">pid</span> <span class="o">=</span> <span class="n">Popen</span><span class="p">([</span><span class="s2">&quot;/bin/mycmd&quot;</span><span class="p">,</span> <span class="s2">&quot;myarg&quot;</span><span class="p">])</span><span class="o">.</span><span class="n">pid</span>

  1623. </pre></div>

  1624. </div>

  1625. <p>P_WAIT example:</p>

  1626. <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">&quot;/bin/mycmd&quot;</span><span class="p">,</span> <span class="s2">&quot;mycmd&quot;</span><span class="p">,</span> <span class="s2">&quot;myarg&quot;</span><span class="p">)</span>

  1627. <span class="o">==&gt;</span>

  1628. <span class="n">retcode</span> <span class="o">=</span> <span class="n">call</span><span class="p">([</span><span class="s2">&quot;/bin/mycmd&quot;</span><span class="p">,</span> <span class="s2">&quot;myarg&quot;</span><span class="p">])</span>

  1629. </pre></div>

  1630. </div>

  1631. <p>Vector example:</p>

  1632. <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>

  1633. <span class="o">==&gt;</span>

  1634. <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>

  1635. </pre></div>

  1636. </div>

  1637. <p>Environment example:</p>

  1638. <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">&quot;/bin/mycmd&quot;</span><span class="p">,</span> <span class="s2">&quot;mycmd&quot;</span><span class="p">,</span> <span class="s2">&quot;myarg&quot;</span><span class="p">,</span> <span class="n">env</span><span class="p">)</span>

  1639. <span class="o">==&gt;</span>

  1640. <span class="n">Popen</span><span class="p">([</span><span class="s2">&quot;/bin/mycmd&quot;</span><span class="p">,</span> <span class="s2">&quot;myarg&quot;</span><span class="p">],</span> <span class="n">env</span><span class="o">=</span><span class="p">{</span><span class="s2">&quot;PATH&quot;</span><span class="p">:</span> <span class="s2">&quot;/usr/bin&quot;</span><span class="p">})</span>

  1641. </pre></div>

  1642. </div>

  1643. </section>

  1644. <section id="replacing-os-popen-os-popen2-os-popen3">

  1645. <h3>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="Link to this heading">¶</a></h3>

  1646. <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>

  1647. <span class="o">==&gt;</span>

  1648. <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>

  1649.           <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>

  1650. <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>

  1651. </pre></div>

  1652. </div>

  1653. <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>

  1654.  <span class="n">child_stdout</span><span class="p">,</span>

  1655.  <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>

  1656. <span class="o">==&gt;</span>

  1657. <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>

  1658.           <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>

  1659. <span class="p">(</span><span class="n">child_stdin</span><span class="p">,</span>

  1660.  <span class="n">child_stdout</span><span class="p">,</span>

  1661.  <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>

  1662. </pre></div>

  1663. </div>

  1664. <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>

  1665. <span class="o">==&gt;</span>

  1666. <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>

  1667.           <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>

  1668. <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>

  1669. </pre></div>

  1670. </div>

  1671. <p>Return code handling translates as follows:</p>

  1672. <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">&#39;w&#39;</span><span class="p">)</span>

  1673. <span class="o">...</span>

  1674. <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>

  1675. <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">&gt;&gt;</span> <span class="mi">8</span><span class="p">:</span>

  1676.     <span class="nb">print</span><span class="p">(</span><span class="s2">&quot;There were some errors&quot;</span><span class="p">)</span>

  1677. <span class="o">==&gt;</span>

  1678. <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>

  1679. <span class="o">...</span>

  1680. <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>

  1681. <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>

  1682.     <span class="nb">print</span><span class="p">(</span><span class="s2">&quot;There were some errors&quot;</span><span class="p">)</span>

  1683. </pre></div>

  1684. </div>

  1685. </section>

  1686. <section id="replacing-functions-from-the-popen2-module">

  1687. <h3>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="Link to this heading">¶</a></h3>

  1688. <div class="admonition note">

  1689. <p class="admonition-title">Note</p>

  1690. <p>If the cmd argument to popen2 functions is a string, the command is executed

  1691. through /bin/sh.  If it is a list, the command is directly executed.</p>

  1692. </div>

  1693. <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">&quot;somestring&quot;</span><span class="p">,</span> <span class="n">bufsize</span><span class="p">,</span> <span class="n">mode</span><span class="p">)</span>

  1694. <span class="o">==&gt;</span>

  1695. <span class="n">p</span> <span class="o">=</span> <span class="n">Popen</span><span class="p">(</span><span class="s2">&quot;somestring&quot;</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>

  1696.           <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>

  1697. <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>

  1698. </pre></div>

  1699. </div>

  1700. <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">&quot;mycmd&quot;</span><span class="p">,</span> <span class="s2">&quot;myarg&quot;</span><span class="p">],</span> <span class="n">bufsize</span><span class="p">,</span> <span class="n">mode</span><span class="p">)</span>

  1701. <span class="o">==&gt;</span>

  1702. <span class="n">p</span> <span class="o">=</span> <span class="n">Popen</span><span class="p">([</span><span class="s2">&quot;mycmd&quot;</span><span class="p">,</span> <span class="s2">&quot;myarg&quot;</span><span class="p">],</span> <span class="n">bufsize</span><span class="o">=</span><span class="n">bufsize</span><span class="p">,</span>

  1703.           <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>

  1704. <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>

  1705. </pre></div>

  1706. </div>

  1707. <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

  1708. <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>

  1709. <ul class="simple">

  1710. <li><p><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.</p></li>

  1711. <li><p>The <em>capturestderr</em> argument is replaced with the <em>stderr</em> argument.</p></li>

  1712. <li><p><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.</p></li>

  1713. <li><p>popen2 closes all file descriptors by default, but you have to specify

  1714. <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

  1715. all platforms or past Python versions.</p></li>

  1716. </ul>

  1717. </section>

  1718. </section>

  1719. <section id="legacy-shell-invocation-functions">

  1720. <h2>Legacy Shell Invocation Functions<a class="headerlink" href="#legacy-shell-invocation-functions" title="Link to this heading">¶</a></h2>

  1721. <p>This module also provides the following legacy functions from the 2.x

  1722. <code class="docutils literal notranslate"><span class="pre">commands</span></code> module. These operations implicitly invoke the system shell and

  1723. none of the guarantees described above regarding security and exception

  1724. handling consistency are valid for these functions.</p>

  1725. <dl class="py function">

  1726. <dt class="sig sig-object py" id="subprocess.getstatusoutput">

  1727. <span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">getstatusoutput</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">cmd</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">*</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">encoding</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">errors</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.getstatusoutput" title="Link to this definition">¶</a></dt>

  1728. <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>

  1729. <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

  1730. return a 2-tuple <code class="docutils literal notranslate"><span class="pre">(exitcode,</span> <span class="pre">output)</span></code>.

  1731. <em>encoding</em> and <em>errors</em> are used to decode output;

  1732. 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>

  1733. <p>A trailing newline is stripped from the output.

  1734. The exit code for the command can be interpreted as the return code

  1735. of subprocess.  Example:</p>

  1736. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">subprocess</span><span class="o">.</span><span class="n">getstatusoutput</span><span class="p">(</span><span class="s1">&#39;ls /bin/ls&#39;</span><span class="p">)</span>

  1737. <span class="go">(0, &#39;/bin/ls&#39;)</span>

  1738. <span class="gp">&gt;&gt;&gt; </span><span class="n">subprocess</span><span class="o">.</span><span class="n">getstatusoutput</span><span class="p">(</span><span class="s1">&#39;cat /bin/junk&#39;</span><span class="p">)</span>

  1739. <span class="go">(1, &#39;cat: /bin/junk: No such file or directory&#39;)</span>

  1740. <span class="gp">&gt;&gt;&gt; </span><span class="n">subprocess</span><span class="o">.</span><span class="n">getstatusoutput</span><span class="p">(</span><span class="s1">&#39;/bin/junk&#39;</span><span class="p">)</span>

  1741. <span class="go">(127, &#39;sh: /bin/junk: not found&#39;)</span>

  1742. <span class="gp">&gt;&gt;&gt; </span><span class="n">subprocess</span><span class="o">.</span><span class="n">getstatusoutput</span><span class="p">(</span><span class="s1">&#39;/bin/kill $$&#39;</span><span class="p">)</span>

  1743. <span class="go">(-15, &#39;&#39;)</span>

  1744. </pre></div>

  1745. </div>

  1746. <div class="availability docutils container">

  1747. <p><a class="reference internal" href="intro.html#availability"><span class="std std-ref">Availability</span></a>: Unix, Windows.</p>

  1748. </div>

  1749. <div class="versionchanged">

  1750. <p><span class="versionmodified changed">Changed in version 3.3.4: </span>Windows support was added.</p>

  1751. <p>The function now returns (exitcode, output) instead of (status, output)

  1752. as it did in Python 3.3.3 and earlier.  exitcode has the same value as

  1753. <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>

  1754. </div>

  1755. <div class="versionchanged">

  1756. <p><span class="versionmodified changed">Changed in version 3.11: </span>Added the <em>encoding</em> and <em>errors</em> parameters.</p>

  1757. </div>

  1758. </dd></dl>

  1759. 

  1760. <dl class="py function">

  1761. <dt class="sig sig-object py" id="subprocess.getoutput">

  1762. <span class="sig-prename descclassname"><span class="pre">subprocess.</span></span><span class="sig-name descname"><span class="pre">getoutput</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">cmd</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">*</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">encoding</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">errors</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#subprocess.getoutput" title="Link to this definition">¶</a></dt>

  1763. <dd><p>Return output (stdout and stderr) of executing <em>cmd</em> in a shell.</p>

  1764. <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

  1765. value is a string containing the command’s output.  Example:</p>

  1766. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">subprocess</span><span class="o">.</span><span class="n">getoutput</span><span class="p">(</span><span class="s1">&#39;ls /bin/ls&#39;</span><span class="p">)</span>

  1767. <span class="go">&#39;/bin/ls&#39;</span>

  1768. </pre></div>

  1769. </div>

  1770. <div class="availability docutils container">

  1771. <p><a class="reference internal" href="intro.html#availability"><span class="std std-ref">Availability</span></a>: Unix, Windows.</p>

  1772. </div>

  1773. <div class="versionchanged">

  1774. <p><span class="versionmodified changed">Changed in version 3.3.4: </span>Windows support added</p>

  1775. </div>

  1776. <div class="versionchanged">

  1777. <p><span class="versionmodified changed">Changed in version 3.11: </span>Added the <em>encoding</em> and <em>errors</em> parameters.</p>

  1778. </div>

  1779. </dd></dl>

  1780. 

  1781. </section>

  1782. <section id="notes">

  1783. <h2>Notes<a class="headerlink" href="#notes" title="Link to this heading">¶</a></h2>

  1784. <section id="converting-an-argument-sequence-to-a-string-on-windows">

  1785. <span id="converting-argument-sequence"></span><h3>Converting an argument sequence to a string on Windows<a class="headerlink" href="#converting-an-argument-sequence-to-a-string-on-windows" title="Link to this heading">¶</a></h3>

  1786. <p>On Windows, an <em>args</em> sequence is converted to a string that can be parsed

  1787. using the following rules (which correspond to the rules used by the MS C

  1788. runtime):</p>

  1789. <ol class="arabic simple">

  1790. <li><p>Arguments are delimited by white space, which is either a

  1791. space or a tab.</p></li>

  1792. <li><p>A string surrounded by double quotation marks is

  1793. interpreted as a single argument, regardless of white space

  1794. contained within.  A quoted string can be embedded in an

  1795. argument.</p></li>

  1796. <li><p>A double quotation mark preceded by a backslash is

  1797. interpreted as a literal double quotation mark.</p></li>

  1798. <li><p>Backslashes are interpreted literally, unless they

  1799. immediately precede a double quotation mark.</p></li>

  1800. <li><p>If backslashes immediately precede a double quotation mark,

  1801. every pair of backslashes is interpreted as a literal

  1802. backslash.  If the number of backslashes is odd, the last

  1803. backslash escapes the next double quotation mark as

  1804. described in rule 3.</p></li>

  1805. </ol>

  1806. <div class="admonition seealso">

  1807. <p class="admonition-title">See also</p>

  1808. <dl class="simple">

  1809. <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><p>Module which provides function to parse and escape command lines.</p>

  1810. </dd>

  1811. </dl>

  1812. </div>

  1813. </section>

  1814. <section id="disabling-use-of-vfork-or-posix-spawn">

  1815. <span id="disable-posix-spawn"></span><span id="disable-vfork"></span><h3>Disabling use of <code class="docutils literal notranslate"><span class="pre">vfork()</span></code> or <code class="docutils literal notranslate"><span class="pre">posix_spawn()</span></code><a class="headerlink" href="#disabling-use-of-vfork-or-posix-spawn" title="Link to this heading">¶</a></h3>

  1816. <p>On Linux, <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> defaults to using the <code class="docutils literal notranslate"><span class="pre">vfork()</span></code> system call

  1817. internally when it is safe to do so rather than <code class="docutils literal notranslate"><span class="pre">fork()</span></code>. This greatly

  1818. improves performance.</p>

  1819. <p>If you ever encounter a presumed highly unusual situation where you need to

  1820. prevent <code class="docutils literal notranslate"><span class="pre">vfork()</span></code> from being used by Python, you can set the

  1821. <code class="xref py py-const docutils literal notranslate"><span class="pre">subprocess._USE_VFORK</span></code> attribute to a false value.</p>

  1822. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">subprocess</span><span class="o">.</span><span class="n">_USE_VFORK</span> <span class="o">=</span> <span class="kc">False</span>  <span class="c1"># See CPython issue gh-NNNNNN.</span>

  1823. </pre></div>

  1824. </div>

  1825. <p>Setting this has no impact on use of <code class="docutils literal notranslate"><span class="pre">posix_spawn()</span></code> which could use

  1826. <code class="docutils literal notranslate"><span class="pre">vfork()</span></code> internally within its libc implementation.  There is a similar

  1827. <code class="xref py py-const docutils literal notranslate"><span class="pre">subprocess._USE_POSIX_SPAWN</span></code> attribute if you need to prevent use of

  1828. that.</p>

  1829. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">subprocess</span><span class="o">.</span><span class="n">_USE_POSIX_SPAWN</span> <span class="o">=</span> <span class="kc">False</span>  <span class="c1"># See CPython issue gh-NNNNNN.</span>

  1830. </pre></div>

  1831. </div>

  1832. <p>It is safe to set these to false on any Python version. They will have no

  1833. effect on older versions when unsupported. Do not assume the attributes are

  1834. available to read. Despite their names, a true value does not indicate that the

  1835. corresponding function will be used, only that it may be.</p>

  1836. <p>Please file issues any time you have to use these private knobs with a way to

  1837. reproduce the issue you were seeing. Link to that issue from a comment in your

  1838. code.</p>

  1839. <div class="versionadded">

  1840. <p><span class="versionmodified added">New in version 3.8: </span><code class="docutils literal notranslate"><span class="pre">_USE_POSIX_SPAWN</span></code></p>

  1841. </div>

  1842. <div class="versionadded">

  1843. <p><span class="versionmodified added">New in version 3.11: </span><code class="docutils literal notranslate"><span class="pre">_USE_VFORK</span></code></p>

  1844. </div>

  1845. </section>

  1846. </section>

  1847. </section>

  1848. 

  1849. 

  1850.             <div class="clearer"></div>

  1851.           </div>

  1852.         </div>

  1853.       </div>

  1854.       <div class="sphinxsidebar" role="navigation" aria-label="main navigation">

  1855.         <div class="sphinxsidebarwrapper">

  1856.   <div>

  1857.     <h3><a href="../contents.html">Table of Contents</a></h3>

  1858.     <ul>

  1859. <li><a class="reference internal" href="#"><code class="xref py py-mod docutils literal notranslate"><span class="pre">subprocess</span></code> — Subprocess management</a><ul>

  1860. <li><a class="reference internal" href="#using-the-subprocess-module">Using the <code class="xref py py-mod docutils literal notranslate"><span class="pre">subprocess</span></code> Module</a><ul>

  1861. <li><a class="reference internal" href="#frequently-used-arguments">Frequently Used Arguments</a></li>

  1862. <li><a class="reference internal" href="#popen-constructor">Popen Constructor</a></li>

  1863. <li><a class="reference internal" href="#exceptions">Exceptions</a></li>

  1864. </ul>

  1865. </li>

  1866. <li><a class="reference internal" href="#security-considerations">Security Considerations</a></li>

  1867. <li><a class="reference internal" href="#popen-objects">Popen Objects</a></li>

  1868. <li><a class="reference internal" href="#windows-popen-helpers">Windows Popen Helpers</a><ul>

  1869. <li><a class="reference internal" href="#windows-constants">Windows Constants</a></li>

  1870. </ul>

  1871. </li>

  1872. <li><a class="reference internal" href="#older-high-level-api">Older high-level API</a></li>

  1873. <li><a class="reference internal" href="#replacing-older-functions-with-the-subprocess-module">Replacing Older Functions with the <code class="xref py py-mod docutils literal notranslate"><span class="pre">subprocess</span></code> Module</a><ul>

  1874. <li><a class="reference internal" href="#replacing-bin-sh-shell-command-substitution">Replacing <strong class="program">/bin/sh</strong> shell command substitution</a></li>

  1875. <li><a class="reference internal" href="#replacing-shell-pipeline">Replacing shell pipeline</a></li>

  1876. <li><a class="reference internal" href="#replacing-os-system">Replacing <code class="xref py py-func docutils literal notranslate"><span class="pre">os.system()</span></code></a></li>

  1877. <li><a class="reference internal" href="#replacing-the-os-spawn-family">Replacing the <code class="xref py py-func docutils literal notranslate"><span class="pre">os.spawn</span></code> family</a></li>

  1878. <li><a class="reference internal" href="#replacing-os-popen-os-popen2-os-popen3">Replacing <code class="xref py py-func docutils literal notranslate"><span class="pre">os.popen()</span></code>, <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></li>

  1879. <li><a class="reference internal" href="#replacing-functions-from-the-popen2-module">Replacing functions from the <code class="xref py py-mod docutils literal notranslate"><span class="pre">popen2</span></code> module</a></li>

  1880. </ul>

  1881. </li>

  1882. <li><a class="reference internal" href="#legacy-shell-invocation-functions">Legacy Shell Invocation Functions</a></li>

  1883. <li><a class="reference internal" href="#notes">Notes</a><ul>

  1884. <li><a class="reference internal" href="#converting-an-argument-sequence-to-a-string-on-windows">Converting an argument sequence to a string on Windows</a></li>

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