| <!-- |
| Documentation/_templates/layout.html |
| |
| Licensed to the Apache Software Foundation (ASF) under one or more |
| contributor license agreements. See the NOTICE file distributed with |
| this work for additional information regarding copyright ownership. The |
| ASF licenses this file to you under the Apache License, Version 2.0 (the |
| "License"); you may not use this file except in compliance with the |
| License. You may obtain a copy of the License at |
| |
| http://www.apache.org/licenses/LICENSE-2.0 |
| |
| Unless required by applicable law or agreed to in writing, software |
| distributed under the License is distributed on an "AS IS" BASIS, WITHOUT |
| WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the |
| License for the specific language governing permissions and limitations |
| under the License. |
| --> |
| |
| |
| |
| <!DOCTYPE html> |
| <html class="writer-html5" lang="en" > |
| <head> |
| <meta charset="utf-8" /> |
| |
| <meta name="viewport" content="width=device-width, initial-scale=1.0" /> |
| |
| <title>Environment Variables — NuttX latest documentation</title> |
| |
| |
| |
| <link rel="stylesheet" href="../../_static/css/theme.css" type="text/css" /> |
| <link rel="stylesheet" href="../../_static/pygments.css" type="text/css" /> |
| <link rel="stylesheet" href="../../_static/tabs.css" type="text/css" /> |
| <link rel="stylesheet" href="../../_static/custom.css" type="text/css" /> |
| |
| |
| |
| <link rel="shortcut icon" href="../../_static/favicon.ico"/> |
| |
| |
| |
| |
| |
| |
| |
| |
| <!--[if lt IE 9]> |
| <script src="../../_static/js/html5shiv.min.js"></script> |
| <![endif]--> |
| |
| |
| <script type="text/javascript" id="documentation_options" data-url_root="../../" src="../../_static/documentation_options.js"></script> |
| <script src="../../_static/jquery.js"></script> |
| <script src="../../_static/underscore.js"></script> |
| <script src="../../_static/doctools.js"></script> |
| |
| <script type="text/javascript" src="../../_static/js/theme.js"></script> |
| |
| |
| <link rel="index" title="Index" href="../../genindex.html" /> |
| <link rel="search" title="Search" href="../../search.html" /> |
| <link rel="next" title="File System Interfaces" href="10_filesystem.html" /> |
| <link rel="prev" title="Pthread Interfaces" href="08_pthread.html" /> |
| </head> |
| |
| <body class="wy-body-for-nav"> |
| |
| |
| <div class="wy-grid-for-nav"> |
| |
| <nav data-toggle="wy-nav-shift" class="wy-nav-side"> |
| <div class="wy-side-scroll"> |
| <div class="wy-side-nav-search" > |
| |
| |
| <a href="../../index.html" class="icon icon-home"> NuttX |
| |
| |
| |
| |
| <img src="../../_static/NuttX.png" class="logo" alt="Logo"/> |
| |
| </a> |
| |
| <!-- this version selector is quite ugly, should be probably replaced by something |
| more modern --> |
| |
| <div class="version-selector"> |
| <select onchange="javascript:location.href = this.value;"> |
| |
| <option value="../../../latest" selected="selected">latest</option> |
| |
| <option value="../../../10.0.0" >10.0.0</option> |
| |
| <option value="../../../10.0.1" >10.0.1</option> |
| |
| <option value="../../../10.1.0" >10.1.0</option> |
| |
| <option value="../../../10.2.0" >10.2.0</option> |
| |
| <option value="../../../10.3.0" >10.3.0</option> |
| |
| <option value="../../../11.0.0" >11.0.0</option> |
| |
| <option value="../../../12.0.0" >12.0.0</option> |
| |
| <option value="../../../12.1.0" >12.1.0</option> |
| |
| <option value="../../../12.2.0" >12.2.0</option> |
| |
| <option value="../../../12.2.1" >12.2.1</option> |
| |
| <option value="../../../12.3.0" >12.3.0</option> |
| |
| <option value="../../../12.4.0" >12.4.0</option> |
| |
| <option value="../../../12.5.0" >12.5.0</option> |
| |
| <option value="../../../12.5.1" >12.5.1</option> |
| |
| <option value="../../../12.6.0" >12.6.0</option> |
| |
| <option value="../../../12.7.0" >12.7.0</option> |
| |
| <option value="../../../12.8.0" >12.8.0</option> |
| |
| <option value="../../../12.9.0" >12.9.0</option> |
| |
| <option value="../../../12.10.0" >12.10.0</option> |
| |
| <option value="../../../12.11.0" >12.11.0</option> |
| |
| </select> |
| </div> |
| |
| |
| <div role="search"> |
| <form id="rtd-search-form" class="wy-form" action="../../search.html" method="get"> |
| <input type="text" name="q" placeholder="Search docs" /> |
| <input type="hidden" name="check_keywords" value="yes" /> |
| <input type="hidden" name="area" value="default" /> |
| </form> |
| </div> |
| |
| </div> |
| |
| |
| <div class="wy-menu wy-menu-vertical" data-spy="affix" role="navigation" aria-label="main navigation"> |
| |
| |
| |
| |
| |
| |
| <p class="caption"><span class="caption-text">Table of Contents</span></p> |
| <ul class="current"> |
| <li class="toctree-l1"><a class="reference internal" href="../../index.html">Home</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="../../introduction/index.html">Introduction</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="../../quickstart/index.html">Getting Started</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="../../contributing/index.html">Contributing</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="../../introduction/inviolables.html">The Inviolable Principles of NuttX</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="../../platforms/index.html">Supported Platforms</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="../../components/index.html">OS Components</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="../../applications/index.html">Applications</a></li> |
| <li class="toctree-l1 current"><a class="reference internal" href="../index.html">API Reference</a><ul class="current"> |
| <li class="toctree-l2 current"><a class="reference internal" href="index.html">Userspace API</a><ul class="current"> |
| <li class="toctree-l3"><a class="reference internal" href="01_task_control.html">Task Control Interfaces</a></li> |
| <li class="toctree-l3"><a class="reference internal" href="02_task_scheduling.html">Task Scheduling Interfaces</a></li> |
| <li class="toctree-l3"><a class="reference internal" href="03_task_control.html">Task Control Interfaces</a></li> |
| <li class="toctree-l3"><a class="reference internal" href="04_message_queue.html">Named Message Queue Interfaces</a></li> |
| <li class="toctree-l3"><a class="reference internal" href="05_counting_semaphore.html">Counting Semaphore Interfaces</a></li> |
| <li class="toctree-l3"><a class="reference internal" href="06_clocks_timers.html">Clocks and Timers</a></li> |
| <li class="toctree-l3"><a class="reference internal" href="07_signals.html">Signal Interfaces</a></li> |
| <li class="toctree-l3"><a class="reference internal" href="08_pthread.html">Pthread Interfaces</a></li> |
| <li class="toctree-l3 current"><a class="current reference internal" href="#">Environment Variables</a><ul> |
| <li class="toctree-l4"><a class="reference internal" href="#programming-interfaces">Programming Interfaces</a></li> |
| <li class="toctree-l4"><a class="reference internal" href="#disabling-environment-variable-support">Disabling Environment Variable Support</a></li> |
| <li class="toctree-l4"><a class="reference internal" href="#functions">Functions</a></li> |
| </ul> |
| </li> |
| <li class="toctree-l3"><a class="reference internal" href="10_filesystem.html">File System Interfaces</a></li> |
| <li class="toctree-l3"><a class="reference internal" href="11_network.html">Network Interfaces</a></li> |
| <li class="toctree-l3"><a class="reference internal" href="12_shared_memory.html">Shared Memory Interfaces</a></li> |
| <li class="toctree-l3"><a class="reference internal" href="13_boardctl.html">Board IOCTL</a></li> |
| <li class="toctree-l3"><a class="reference internal" href="13_logging.html">Logging</a></li> |
| <li class="toctree-l3"><a class="reference internal" href="structures.html">OS Data Structures</a></li> |
| </ul> |
| </li> |
| <li class="toctree-l2"><a class="reference internal" href="../os/index.html">Architecture APIs</a></li> |
| </ul> |
| </li> |
| <li class="toctree-l1"><a class="reference internal" href="../../faq/index.html">FAQ</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="../../guides/index.html">Guides</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="../../glossary.html">Glossary</a></li> |
| </ul> |
| |
| |
| |
| </div> |
| |
| </div> |
| </nav> |
| |
| <section data-toggle="wy-nav-shift" class="wy-nav-content-wrap"> |
| |
| |
| <nav class="wy-nav-top" aria-label="top navigation"> |
| |
| <i data-toggle="wy-nav-top" class="fa fa-bars"></i> |
| <a href="../../index.html">NuttX</a> |
| |
| </nav> |
| |
| |
| <div class="wy-nav-content"> |
| |
| <div class="rst-content"> |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| <div role="navigation" aria-label="breadcrumbs navigation"> |
| |
| <ul class="wy-breadcrumbs"> |
| |
| <li><a href="../../index.html" class="icon icon-home"></a> »</li> |
| |
| <li><a href="../index.html">API Reference</a> »</li> |
| |
| <li><a href="index.html">Userspace API</a> »</li> |
| |
| <li>Environment Variables</li> |
| |
| |
| <li class="wy-breadcrumbs-aside"> |
| |
| |
| <a href="../../_sources/reference/user/09_env_vars.rst.txt" rel="nofollow"> View page source</a> |
| |
| |
| </li> |
| |
| </ul> |
| |
| |
| <hr/> |
| </div> |
| <div role="main" class="document" itemscope="itemscope" itemtype="http://schema.org/Article"> |
| <div itemprop="articleBody"> |
| |
| <div class="section" id="environment-variables"> |
| <h1>Environment Variables<a class="headerlink" href="#environment-variables" title="Permalink to this headline">¶</a></h1> |
| <p>NuttX supports environment variables that can be used to |
| control the behavior of programs. In the spirit of NuttX the environment |
| variable behavior attempts to emulate the behavior of environment |
| variables in the multi-processing OS:</p> |
| <ul class="simple"> |
| <li><p><strong>Task environments</strong>. When a new task is created using |
| <a class="reference external" href="#taskcreate">task_create</a>, the environment of the child task is |
| an inherited, exact copy of the environment of the parent. However, |
| after child task has been created, subsequent operations by the child |
| task on its environment does not alter the environment of the parent. |
| No do operations by the parent effect the child’s environment. The |
| environments start identical but are independent and may diverge.</p></li> |
| <li><p><strong>Thread environments</strong>. When a pthread is created using |
| <a class="reference external" href="#pthreadcreate">pthread_create</a>, the child thread also inherits |
| that environment of the parent. However, the child does not receive a |
| copy of the environment but, rather, shares the same environment. |
| Changes to the environment are visible to all threads with the same |
| parentage.</p></li> |
| </ul> |
| <div class="section" id="programming-interfaces"> |
| <h2>Programming Interfaces<a class="headerlink" href="#programming-interfaces" title="Permalink to this headline">¶</a></h2> |
| <p>The following environment variable |
| programming interfaces are provided by NuttX and are described in detail |
| in the following paragraphs.</p> |
| <blockquote> |
| <div><ul class="simple"> |
| <li><p><a class="reference internal" href="#c.getenv" title="getenv"><code class="xref c c-func docutils literal notranslate"><span class="pre">getenv()</span></code></a></p></li> |
| <li><p><a class="reference internal" href="#c.putenv" title="putenv"><code class="xref c c-func docutils literal notranslate"><span class="pre">putenv()</span></code></a></p></li> |
| <li><p><a class="reference internal" href="#c.clearenv" title="clearenv"><code class="xref c c-func docutils literal notranslate"><span class="pre">clearenv()</span></code></a></p></li> |
| <li><p><a class="reference internal" href="#c.setenv" title="setenv"><code class="xref c c-func docutils literal notranslate"><span class="pre">setenv()</span></code></a></p></li> |
| <li><p><a class="reference internal" href="#c.unsetenv" title="unsetenv"><code class="xref c c-func docutils literal notranslate"><span class="pre">unsetenv()</span></code></a></p></li> |
| </ul> |
| </div></blockquote> |
| </div> |
| <div class="section" id="disabling-environment-variable-support"> |
| <h2>Disabling Environment Variable Support<a class="headerlink" href="#disabling-environment-variable-support" title="Permalink to this headline">¶</a></h2> |
| <p>All support for environment |
| variables can be disabled by setting <code class="docutils literal notranslate"><span class="pre">CONFIG_DISABLE_ENVIRON</span></code> in the |
| board configuration file.</p> |
| </div> |
| <div class="section" id="functions"> |
| <h2>Functions<a class="headerlink" href="#functions" title="Permalink to this headline">¶</a></h2> |
| <dl class="c function"> |
| <dt id="c.getenv"> |
| <span class="pre">FAR</span> <span class="pre">char</span> <span class="pre">*</span><code class="sig-name descname"><span class="pre">getenv</span></code><span class="sig-paren">(</span><em class="property"><span class="pre">const</span></em> <span class="pre">char</span> <span class="pre">*</span><em><span class="pre">name</span></em><span class="sig-paren">)</span><a class="headerlink" href="#c.getenv" title="Permalink to this definition">¶</a><br /></dt> |
| <dd><p>Searches the environment list for a string that matches |
| the string pointed to by <code class="docutils literal notranslate"><span class="pre">name</span></code>.</p> |
| <dl class="field-list simple"> |
| <dt class="field-odd">Parameters</dt> |
| <dd class="field-odd"><ul class="simple"> |
| <li><p><strong>name</strong> – The name of the variable to find.</p></li> |
| </ul> |
| </dd> |
| <dt class="field-even">Returns</dt> |
| <dd class="field-even"><p>The value of the variable (read-only) or NULL on failure.</p> |
| </dd> |
| </dl> |
| </dd></dl> |
| |
| <dl class="c function"> |
| <dt id="c.putenv"> |
| <span class="pre">int</span> <code class="sig-name descname"><span class="pre">putenv</span></code><span class="sig-paren">(</span><span class="pre">char</span> <span class="pre">*</span><em><span class="pre">string</span></em><span class="sig-paren">)</span><a class="headerlink" href="#c.putenv" title="Permalink to this definition">¶</a><br /></dt> |
| <dd><p>Adds or changes the value of environment variables. The |
| argument string is of the form <code class="docutils literal notranslate"><span class="pre">name=value</span></code>. If name does |
| not already exist in the environment, then string is added |
| to the environment. If name does exist, then the value of name in the |
| environment is changed to value.</p> |
| <dl class="field-list simple"> |
| <dt class="field-odd">Parameters</dt> |
| <dd class="field-odd"><ul class="simple"> |
| <li><p><strong>string</strong> – <code class="docutils literal notranslate"><span class="pre">name=value</span></code> string describing the environment setting to |
| add/modify.</p></li> |
| </ul> |
| </dd> |
| <dt class="field-even">Returns</dt> |
| <dd class="field-even"><p>Zero on success.</p> |
| </dd> |
| </dl> |
| </dd></dl> |
| |
| <dl class="c function"> |
| <dt id="c.clearenv"> |
| <span class="pre">int</span> <code class="sig-name descname"><span class="pre">clearenv</span></code><span class="sig-paren">(</span><span class="pre">void</span><span class="sig-paren">)</span><a class="headerlink" href="#c.clearenv" title="Permalink to this definition">¶</a><br /></dt> |
| <dd><p>Clears the environment of all name-value pairs and sets |
| the value of the external variable environ to NULL.</p> |
| <dl class="field-list simple"> |
| <dt class="field-odd">Returns</dt> |
| <dd class="field-odd"><p>Zero on success.</p> |
| </dd> |
| </dl> |
| </dd></dl> |
| |
| <dl class="c function"> |
| <dt id="c.setenv"> |
| <span class="pre">int</span> <code class="sig-name descname"><span class="pre">setenv</span></code><span class="sig-paren">(</span><em class="property"><span class="pre">const</span></em> <span class="pre">char</span> <span class="pre">*</span><em><span class="pre">name</span></em>, <em class="property"><span class="pre">const</span></em> <span class="pre">char</span> <span class="pre">*</span><em><span class="pre">value</span></em>, <span class="pre">int</span> <em><span class="pre">overwrite</span></em><span class="sig-paren">)</span><a class="headerlink" href="#c.setenv" title="Permalink to this definition">¶</a><br /></dt> |
| <dd><p>Adds the variable <code class="docutils literal notranslate"><span class="pre">name</span></code> to the environment with the specified |
| <code class="docutils literal notranslate"><span class="pre">value</span></code> if the variable <code class="docutils literal notranslate"><span class="pre">name</span></code> does not exist. If the <code class="docutils literal notranslate"><span class="pre">name</span></code> |
| does exist in the environment, then its value is changed to <code class="docutils literal notranslate"><span class="pre">value</span></code> |
| if <code class="docutils literal notranslate"><span class="pre">overwrite</span></code> is non-zero; if |
| <code class="docutils literal notranslate"><span class="pre">overwrite</span></code> is zero, then the value of <code class="docutils literal notranslate"><span class="pre">name</span></code> is unaltered.</p> |
| <dl class="field-list simple"> |
| <dt class="field-odd">Parameters</dt> |
| <dd class="field-odd"><ul class="simple"> |
| <li><p><strong>name</strong> – The name of the variable to change.</p></li> |
| <li><p><strong>value</strong> – The new value of the variable.</p></li> |
| <li><p><strong>value</strong> – Replace any existing value if non-zero.</p></li> |
| </ul> |
| </dd> |
| <dt class="field-even">Returns</dt> |
| <dd class="field-even"><p>Zero on success.</p> |
| </dd> |
| </dl> |
| </dd></dl> |
| |
| <dl class="c function"> |
| <dt id="c.unsetenv"> |
| <span class="pre">int</span> <code class="sig-name descname"><span class="pre">unsetenv</span></code><span class="sig-paren">(</span><em class="property"><span class="pre">const</span></em> <span class="pre">char</span> <span class="pre">*</span><em><span class="pre">name</span></em><span class="sig-paren">)</span><a class="headerlink" href="#c.unsetenv" title="Permalink to this definition">¶</a><br /></dt> |
| <dd><p>Deletes the variable <code class="docutils literal notranslate"><span class="pre">name</span></code> from the environment.</p> |
| <dl class="field-list simple"> |
| <dt class="field-odd">Parameters</dt> |
| <dd class="field-odd"><ul class="simple"> |
| <li><p><strong>name</strong> – The name of the variable to delete.</p></li> |
| </ul> |
| </dd> |
| <dt class="field-even">Returns</dt> |
| <dd class="field-even"><p>Zero on success.</p> |
| </dd> |
| </dl> |
| </dd></dl> |
| |
| </div> |
| </div> |
| |
| |
| </div> |
| |
| </div> |
| <footer> |
| <div class="rst-footer-buttons" role="navigation" aria-label="footer navigation"> |
| <a href="10_filesystem.html" class="btn btn-neutral float-right" title="File System Interfaces" accesskey="n" rel="next">Next <span class="fa fa-arrow-circle-right" aria-hidden="true"></span></a> |
| <a href="08_pthread.html" class="btn btn-neutral float-left" title="Pthread Interfaces" accesskey="p" rel="prev"><span class="fa fa-arrow-circle-left" aria-hidden="true"></span> Previous</a> |
| </div> |
| |
| <hr/> |
| |
| <div role="contentinfo"> |
| <p> |
| © Copyright 2020, The Apache Software Foundation. |
| |
| </p> |
| </div> |
| |
| </footer> |
| </div> |
| </div> |
| |
| </section> |
| |
| </div> |
| |
| |
| <script type="text/javascript"> |
| jQuery(function () { |
| SphinxRtdTheme.Navigation.enable(true); |
| }); |
| </script> |
| |
| |
| |
| |
| |
| |
| </body> |
| </html> |
