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  <section id="task-control-interfaces">
<h1>Task Control Interfaces<a class="headerlink" href="#task-control-interfaces" title="Permalink to this heading"></a></h1>
<p><strong>Tasks</strong>. NuttX is a flat address OS. As such it does not support
<em>processes</em> in the way that, say, Linux does. NuttX only supports simple
threads running within the same address space. However, the programming
model makes a distinction between <em>tasks</em> and <em>pthreads</em>:</p>
<blockquote>
<div><ul class="simple">
<li><p><em>tasks</em> are threads which have a degree of independence</p></li>
<li><p><a class="reference external" href="#Pthread">pthreads</a> share some resources.</p></li>
</ul>
</div></blockquote>
<p><strong>File Descriptors and Streams</strong>. This applies, in particular, in the
area of opened file descriptors and streams. When a task is started
using the interfaces in this section, it will be created with at most
three open files.</p>
<p>If <code class="docutils literal notranslate"><span class="pre">CONFIG_DEV_CONSOLE</span></code> is defined, the first three file descriptors
(corresponding to stdin, stdout, stderr) will be duplicated for the new
task. Since these file descriptors are duplicated, the child task can
free close them or manipulate them in any way without effecting the
parent task. File-related operations (open, close, etc.) within a task
will have no effect on other tasks. Since the three file descriptors are
duplicated, it is also possible to perform some level of redirection.</p>
<p>pthreads, on the other hand, will always share file descriptors with the
parent thread. In this case, file operations will have effect only all
pthreads the were started from the same parent thread.</p>
<p><strong>Executing Programs within a File System</strong>. NuttX also provides
internal interfaces for the execution of separately built programs that
reside in a file system. These internal interfaces are, however,
non-standard and are documented with the NuttX binary
loader and NXFLAT documentation.</p>
<p><strong>Task Control Interfaces</strong>. The following task control interfaces are
provided by NuttX:</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>Maybe this can be converted into a table, or could otherwise
be replaced by the index if these are sectioned in this way.</p>
</div>
<p>Non-standard task control interfaces inspired by VxWorks interfaces:</p>
<blockquote>
<div><ul class="simple">
<li><p><a class="reference internal" href="#c.task_create" title="task_create"><code class="xref c c-func docutils literal notranslate"><span class="pre">task_create()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.task_delete" title="task_delete"><code class="xref c c-func docutils literal notranslate"><span class="pre">task_delete()</span></code></a></p></li>
<li><p><code class="xref c c-func docutils literal notranslate"><span class="pre">task_restart()</span></code></p></li>
</ul>
</div></blockquote>
<p>Non-standard extensions to VxWorks-like interfaces to support POSIX
<a class="reference external" href="https://cwiki.apache.org/confluence/display/NUTTX/Cancellation+Points">Cancellation
Points</a>.</p>
<blockquote>
<div><ul class="simple">
<li><p><a class="reference internal" href="#c.task_setcancelstate" title="task_setcancelstate"><code class="xref c c-func docutils literal notranslate"><span class="pre">task_setcancelstate()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.task_setcanceltype" title="task_setcanceltype"><code class="xref c c-func docutils literal notranslate"><span class="pre">task_setcanceltype()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.task_testcancel" title="task_testcancel"><code class="xref c c-func docutils literal notranslate"><span class="pre">task_testcancel()</span></code></a></p></li>
</ul>
</div></blockquote>
<p>Standard interfaces</p>
<blockquote>
<div><ul class="simple">
<li><p><a class="reference internal" href="#c.exit" title="exit"><code class="xref c c-func docutils literal notranslate"><span class="pre">exit()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.getpid" title="getpid"><code class="xref c c-func docutils literal notranslate"><span class="pre">getpid()</span></code></a></p></li>
</ul>
</div></blockquote>
<p>Standard <code class="docutils literal notranslate"><span class="pre">vfork</span></code> and <code class="docutils literal notranslate"><span class="pre">exec[v|l]</span></code> interfaces:</p>
<blockquote>
<div><ul class="simple">
<li><p><a class="reference internal" href="#c.vfork" title="vfork"><code class="xref c c-func docutils literal notranslate"><span class="pre">vfork()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.exec" title="exec"><code class="xref c c-func docutils literal notranslate"><span class="pre">exec()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.execv" title="execv"><code class="xref c c-func docutils literal notranslate"><span class="pre">execv()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.execl" title="execl"><code class="xref c c-func docutils literal notranslate"><span class="pre">execl()</span></code></a></p></li>
</ul>
</div></blockquote>
<p>Standard <code class="docutils literal notranslate"><span class="pre">posix_spawn</span></code> interfaces:</p>
<blockquote>
<div><ul class="simple">
<li><p><a class="reference internal" href="#c.posix_spawn" title="posix_spawn"><code class="xref c c-func docutils literal notranslate"><span class="pre">posix_spawn()</span></code></a> and <a class="reference internal" href="#c.posix_spawnp" title="posix_spawnp"><code class="xref c c-func docutils literal notranslate"><span class="pre">posix_spawnp()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.posix_spawn_file_actions_init" title="posix_spawn_file_actions_init"><code class="xref c c-func docutils literal notranslate"><span class="pre">posix_spawn_file_actions_init()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.posix_spawn_file_actions_destroy" title="posix_spawn_file_actions_destroy"><code class="xref c c-func docutils literal notranslate"><span class="pre">posix_spawn_file_actions_destroy()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.posix_spawn_file_actions_addclose" title="posix_spawn_file_actions_addclose"><code class="xref c c-func docutils literal notranslate"><span class="pre">posix_spawn_file_actions_addclose()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.posix_spawn_file_actions_adddup2" title="posix_spawn_file_actions_adddup2"><code class="xref c c-func docutils literal notranslate"><span class="pre">posix_spawn_file_actions_adddup2()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.posix_spawn_file_actions_addopen" title="posix_spawn_file_actions_addopen"><code class="xref c c-func docutils literal notranslate"><span class="pre">posix_spawn_file_actions_addopen()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.posix_spawnattr_init" title="posix_spawnattr_init"><code class="xref c c-func docutils literal notranslate"><span class="pre">posix_spawnattr_init()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.posix_spawnattr_getflags" title="posix_spawnattr_getflags"><code class="xref c c-func docutils literal notranslate"><span class="pre">posix_spawnattr_getflags()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.posix_spawnattr_getschedparam" title="posix_spawnattr_getschedparam"><code class="xref c c-func docutils literal notranslate"><span class="pre">posix_spawnattr_getschedparam()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.posix_spawnattr_getschedpolicy" title="posix_spawnattr_getschedpolicy"><code class="xref c c-func docutils literal notranslate"><span class="pre">posix_spawnattr_getschedpolicy()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.posix_spawnattr_getsigmask" title="posix_spawnattr_getsigmask"><code class="xref c c-func docutils literal notranslate"><span class="pre">posix_spawnattr_getsigmask()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.posix_spawnattr_setflags" title="posix_spawnattr_setflags"><code class="xref c c-func docutils literal notranslate"><span class="pre">posix_spawnattr_setflags()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.posix_spawnattr_setschedparam" title="posix_spawnattr_setschedparam"><code class="xref c c-func docutils literal notranslate"><span class="pre">posix_spawnattr_setschedparam()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.posix_spawnattr_setschedpolicy" title="posix_spawnattr_setschedpolicy"><code class="xref c c-func docutils literal notranslate"><span class="pre">posix_spawnattr_setschedpolicy()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.posix_spawnattr_setsigmask" title="posix_spawnattr_setsigmask"><code class="xref c c-func docutils literal notranslate"><span class="pre">posix_spawnattr_setsigmask()</span></code></a></p></li>
</ul>
</div></blockquote>
<p>Non-standard task control interfaces inspired by <code class="docutils literal notranslate"><span class="pre">posix_spawn</span></code>:</p>
<blockquote>
<div><ul class="simple">
<li><p><a class="reference internal" href="#c.task_spawn" title="task_spawn"><code class="xref c c-func docutils literal notranslate"><span class="pre">task_spawn()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.posix_spawnattr_getstacksize" title="posix_spawnattr_getstacksize"><code class="xref c c-func docutils literal notranslate"><span class="pre">posix_spawnattr_getstacksize()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.posix_spawnattr_setstacksize" title="posix_spawnattr_setstacksize"><code class="xref c c-func docutils literal notranslate"><span class="pre">posix_spawnattr_setstacksize()</span></code></a></p></li>
</ul>
</div></blockquote>
<section id="functions">
<h2>Functions<a class="headerlink" href="#functions" title="Permalink to this heading"></a></h2>
<dl class="c function">
<dt class="sig sig-object c" id="c.task_create">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">task_create</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">name</span></span>, <span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">priority</span></span>, <span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">stack_size</span></span>, <a class="reference internal" href="structures.html#c.main_t" title="main_t"><span class="n"><span class="pre">main_t</span></span></a><span class="w"> </span><span class="n"><span class="pre">entry</span></span>, <span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="n"><span class="pre">argv</span></span><span class="p"><span class="pre">[</span></span><span class="p"><span class="pre">]</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.task_create" title="Permalink to this definition"></a><br /></dt>
<dd><p>This function creates and activates a new task with a
specified priority and returns its system-assigned ID.</p>
<p>The entry address entry is the address of the “main” function of the
task. This function will be called once the C environment has been set
up. The specified function will be called with four arguments. Should
the specified routine return, a call to <a class="reference internal" href="#c.exit" title="exit"><code class="xref c c-func docutils literal notranslate"><span class="pre">exit()</span></code></a> will automatically be
made.</p>
<p>Note that an arbitrary number of arguments may be passed to the spawned
functions.</p>
<p>The arguments are copied (via <code class="docutils literal notranslate"><span class="pre">strdup</span></code>) so that the life of the passed
strings is not dependent on the life of the caller to <a class="reference internal" href="#c.task_create" title="task_create"><code class="xref c c-func docutils literal notranslate"><span class="pre">task_create()</span></code></a>.</p>
<p>The newly created task does not inherit scheduler characteristics from
the parent task: The new task is started at the default system priority
and with the <code class="docutils literal notranslate"><span class="pre">SCHED_FIFO</span></code> scheduling policy. These characteristics may be
modified after the new task has been started.</p>
<p>The newly created task does inherit the first three file descriptors
(corresponding to stdin, stdout, and stderr) and redirection of standard
I/O is supported.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters<span class="colon">:</span></dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>name</strong> – Name of the new task</p></li>
<li><p><strong>priority</strong> – Priority of the new task</p></li>
<li><p><strong>stack_size</strong> – size (in bytes) of the stack needed</p></li>
<li><p><strong>entry</strong> – Entry point of a new task</p></li>
<li><p><strong>argv</strong> – A pointer to an array of input parameters. The array should
be terminated with a NULL argv[] value. If no parameters are
required, argv may be NULL.</p></li>
</ul>
</dd>
<dt class="field-even">Returns<span class="colon">:</span></dt>
<dd class="field-even"><p>the non-zero task ID of the new task or ERROR if memory is
insufficient or the task cannot be created
(<code class="docutils literal notranslate"><span class="pre">`errno</span></code> &lt;#ErrnoAccess&gt;`__ is not set).</p>
</dd>
</dl>
<p><strong>Defined in:</strong> <code class="docutils literal notranslate"><span class="pre">sched.h</span></code></p>
<p><strong>POSIX Compatibility:</strong> This is a NON-POSIX interface. VxWorks provides
the following similar interface:</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="kt">int</span><span class="w"> </span><span class="nf">taskSpawn</span><span class="p">(</span><span class="kt">char</span><span class="w"> </span><span class="o">*</span><span class="n">name</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">priority</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">options</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">stackSize</span><span class="p">,</span><span class="w"> </span><span class="n">FUNCPTR</span><span class="w"> </span><span class="n">entryPt</span><span class="p">,</span>
<span class="w">              </span><span class="kt">int</span><span class="w"> </span><span class="n">arg1</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">arg2</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">arg3</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">arg4</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">arg5</span><span class="p">,</span>
<span class="w">              </span><span class="kt">int</span><span class="w"> </span><span class="n">arg6</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">arg7</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">arg8</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">arg9</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">arg10</span><span class="p">);</span>
</pre></div>
</div>
<p>The NuttX <a class="reference internal" href="#c.task_create" title="task_create"><code class="xref c c-func docutils literal notranslate"><span class="pre">task_create()</span></code></a> differs from VxWorks’ <code class="xref c c-func docutils literal notranslate"><span class="pre">taskSpawn()</span></code> in the
following ways:</p>
<blockquote>
<div><ul class="simple">
<li><p>Interface name</p></li>
<li><p>Various differences in types of arguments</p></li>
<li><p>There is no options argument.</p></li>
<li><p>A variable number of parameters can be passed to a task (VxWorks
supports ten).</p></li>
</ul>
</div></blockquote>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.task_delete">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">task_delete</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.pid_t" title="pid_t"><span class="n"><span class="pre">pid_t</span></span></a><span class="w"> </span><span class="n"><span class="pre">pid</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.task_delete" title="Permalink to this definition"></a><br /></dt>
<dd><p>This function causes a specified task to cease to
exist. Its stack and TCB will be deallocated. This function is the
companion to <code class="docutils literal notranslate"><span class="pre">task_create()</span></code>. This is the version of the function
exposed to the user; it is simply a wrapper around the internal,
<code class="docutils literal notranslate"><span class="pre">nxtask_terminate()</span></code> function.</p>
<p>The logic in this function only deletes non-running tasks. If the
<code class="docutils literal notranslate"><span class="pre">pid</span></code> parameter refers to the currently running task, then processing
is redirected to <code class="docutils literal notranslate"><span class="pre">exit()</span></code>. This can only happen if a task calls
<code class="docutils literal notranslate"><span class="pre">task_delete()</span></code> in order to delete itself.</p>
<p>This function obeys the semantics of pthread cancellation: task deletion
is deferred if cancellation is disabled or if deferred cancellation is
supported (with <a class="reference external" href="https://cwiki.apache.org/confluence/display/NUTTX/Cancellation+Points">Cancellation
Points</a>
enabled).</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters<span class="colon">:</span></dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>pid</strong> – The task ID of the task to delete. An ID of zero signifies
the calling task. Any attempt by the calling task will be
automatically re-directed to <code class="docutils literal notranslate"><span class="pre">exit()</span></code>.</p></li>
</ul>
</dd>
<dt class="field-even">Returns<span class="colon">:</span></dt>
<dd class="field-even"><p><code class="docutils literal notranslate"><span class="pre">OK</span></code>, or <code class="docutils literal notranslate"><span class="pre">ERROR</span></code> if the task cannot be deleted. The
<code class="docutils literal notranslate"><span class="pre">`errno</span></code> &lt;#ErrnoAccess&gt;`__ is set to indicate the nature of the
failure. This function can fail, for example, if the provided pid
does not correspond to a currently executing task.</p>
</dd>
</dl>
<p><strong>Assumptions/Limitations:</strong></p>
<p><code class="docutils literal notranslate"><span class="pre">task_delete()</span></code> must be used with caution: If the task holds resources
(for example, allocated memory or semaphores needed by other tasks),
then <code class="docutils literal notranslate"><span class="pre">task_delete()</span></code> can strand those resources.</p>
<p><strong>POSIX Compatibility:</strong> This is a NON-POSIX interface. VxWorks provides
the following similar interface:</p>
<p>The NuttX task_delete() differs from VxWorks’ taskDelete() in the
following ways:</p>
<ul class="simple">
<li><p>No support is provided for calling the tasks deletion routines
(because the VxWorks <code class="docutils literal notranslate"><span class="pre">taskDeleteHookAdd()</span></code> is not supported).
However, if <code class="docutils literal notranslate"><span class="pre">atexit()</span></code> or <code class="docutils literal notranslate"><span class="pre">on_exit</span></code> support is enabled, those
will be called when the task deleted.</p></li>
<li><p>Deletion of self is supported, but only because <code class="docutils literal notranslate"><span class="pre">task_delete()</span></code>
will re-direct processing to <code class="docutils literal notranslate"><span class="pre">exit()</span></code>.</p></li>
</ul>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.task_setcancelstate">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">task_setcancelstate</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">state</span></span>, <span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">oldstate</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.task_setcancelstate" title="Permalink to this definition"></a><br /></dt>
<dd><p>This function atomically sets
both the calling task’s cancellability state to the indicated state and
returns the previous cancellability state at the location referenced by
oldstate. Legal values for state are TASK_CANCEL_ENABLE and
TASK_CANCEL_DISABLE.</p>
<p>Any pending thread cancellation may occur at the time that the
cancellation state is set to TASK_CANCEL_ENABLE.</p>
<p>The cancellability state and type of any newly created tasks are
TASK_CANCEL_ENABLE and TASK_CANCEL_DEFERRED respectively.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters<span class="colon">:</span></dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>state</strong> – New cancellation state. One of PTHREAD_CANCEL_ENABLE or
PTHREAD_CANCEL_DISABLE.</p></li>
<li><p><strong>oldstate</strong> – Location to return the previous cancellation state.</p></li>
</ul>
</dd>
<dt class="field-even">Returns<span class="colon">:</span></dt>
<dd class="field-even"><p><p>Zero (<code class="docutils literal notranslate"><span class="pre">OK</span></code>) on success; <code class="docutils literal notranslate"><span class="pre">ERROR</span></code> is returned on any failure
with the <code class="docutils literal notranslate"><span class="pre">errno</span></code> value set appropriately:</p>
<blockquote>
<div><ul class="simple">
<li><p><code class="docutils literal notranslate"><span class="pre">ESRCH</span></code>. No thread could be found corresponding to that specified
by the given thread ID.</p></li>
</ul>
</div></blockquote>
</p>
</dd>
</dl>
<p><strong>POSIX Compatibility:</strong> This is a non-standard interface. It extends
the functionality of <code class="docutils literal notranslate"><span class="pre">pthread_setcancelstate()</span></code> to tasks and supports
use of <code class="docutils literal notranslate"><span class="pre">task_delete()</span></code>.</p>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.task_setcanceltype">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">task_setcanceltype</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">type</span></span>, <span class="pre">FAR</span><span class="w"> </span><span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">oldtype</span></span><span class="sig-paren">)</span><span class="p"><span class="pre">;</span></span><a class="headerlink" href="#c.task_setcanceltype" title="Permalink to this definition"></a><br /></dt>
<dd><p>This function atomically both
sets the calling task’s cancellability type to the indicated type and
returns the previous cancellability type at the location referenced by
<code class="docutils literal notranslate"><span class="pre">oldtype</span></code>. Legal values for type are <code class="docutils literal notranslate"><span class="pre">TASK_CANCEL_DEFERRED</span></code> and
<code class="docutils literal notranslate"><span class="pre">TASK_CANCEL_ASYNCHRONOUS</span></code>.</p>
<p>The cancellability state and type of any newly created tasks are
<code class="docutils literal notranslate"><span class="pre">TASK_CANCEL_ENABLE</span></code> and <code class="docutils literal notranslate"><span class="pre">TASK_CANCEL_DEFERRED</span></code> respectively.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters<span class="colon">:</span></dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>type</strong> – New cancellation state. One of <code class="docutils literal notranslate"><span class="pre">PTHREAD_CANCEL_DEFERRED</span></code>
or <code class="docutils literal notranslate"><span class="pre">PTHREAD_CANCEL_ASYNCHRONOUS</span></code>.</p></li>
<li><p><strong>oldtype</strong> – Location to return the previous cancellation type.</p></li>
</ul>
</dd>
<dt class="field-even">Returns<span class="colon">:</span></dt>
<dd class="field-even"><p><p>Zero (<code class="docutils literal notranslate"><span class="pre">OK</span></code>) on success; <code class="docutils literal notranslate"><span class="pre">ERROR</span></code> is returned on any failure with the
<code class="docutils literal notranslate"><span class="pre">errno</span></code> value set appropriately:</p>
<ul class="simple">
<li><p><code class="docutils literal notranslate"><span class="pre">ESRCH</span></code>. No thread could be found corresponding to that specified
by the given thread ID.</p></li>
</ul>
</p>
</dd>
</dl>
<p><strong>POSIX Compatibility:</strong> This is a non-standard interface. It extends
the functionality of <code class="docutils literal notranslate"><span class="pre">pthread_setcanceltype()</span></code> to tasks and supports
use of <code class="docutils literal notranslate"><span class="pre">task_delete()</span></code>.</p>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.task_testcancel">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">task_testcancel</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">void</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.task_testcancel" title="Permalink to this definition"></a><br /></dt>
<dd><p>Creates a <a class="reference external" href="https://cwiki.apache.org/confluence/display/NUTTX/Cancellation+Points">Cancellation
Point</a>
in the calling task. The <code class="docutils literal notranslate"><span class="pre">task_testcancel()</span></code> function has no effect if
cancellability is disabled.</p>
<p><strong>POSIX Compatibility:</strong> This is a non-standard interface. It extends
the functionality of <code class="docutils literal notranslate"><span class="pre">pthread_testcancel()</span></code> to tasks and supports use
of <code class="docutils literal notranslate"><span class="pre">task_delete()</span></code>.</p>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.exit">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">exit</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">code</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.exit" title="Permalink to this definition"></a><br /></dt>
<dd></dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c._exit">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">_exit</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">code</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c._exit" title="Permalink to this definition"></a><br /></dt>
<dd><p>Causes the calling task to cease to exist
– its stack and TCB will be deallocated. exit differs from _exit in
that it flushes streams, closes file descriptors and will execute any
function registered with <code class="docutils literal notranslate"><span class="pre">atexit()</span></code> or <code class="docutils literal notranslate"><span class="pre">on_exit()</span></code>.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters<span class="colon">:</span></dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>code</strong> – (ignored)</p></li>
</ul>
</dd>
</dl>
<p><strong>POSIX Compatibility:</strong> This is equivalent to the ANSI interface:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>void exit(int code);
</pre></div>
</div>
<p>And the UNIX interface:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>void _exit(int code);
</pre></div>
</div>
<p>The NuttX exit() differs from ANSI exit() in the following ways:</p>
<blockquote>
<div><ul class="simple">
<li><p>The <code class="docutils literal notranslate"><span class="pre">code</span></code> parameter is ignored.</p></li>
</ul>
</div></blockquote>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.getpid">
<a class="reference internal" href="structures.html#c.pid_t" title="pid_t"><span class="n"><span class="pre">pid_t</span></span></a><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">getpid</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">void</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.getpid" title="Permalink to this definition"></a><br /></dt>
<dd></dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.vfork">
<a class="reference internal" href="structures.html#c.pid_t" title="pid_t"><span class="n"><span class="pre">pid_t</span></span></a><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">vfork</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">void</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.vfork" title="Permalink to this definition"></a><br /></dt>
<dd><p>The <code class="docutils literal notranslate"><span class="pre">vfork()</span></code> function has the same effect as
<code class="docutils literal notranslate"><span class="pre">fork()</span></code>, except that the behavior is undefined if the process created
by <code class="docutils literal notranslate"><span class="pre">vfork()</span></code> either modifies any data other than a variable of type
<code class="docutils literal notranslate"><span class="pre">pid_t</span></code> used to store the return value from <code class="docutils literal notranslate"><span class="pre">vfork()</span></code>, or returns
from the function in which <code class="docutils literal notranslate"><span class="pre">vfork()</span></code> was called, or calls any other
function before successfully calling <code class="docutils literal notranslate"><span class="pre">_exit()</span></code> or one of the <code class="docutils literal notranslate"><span class="pre">exec</span></code>
family of functions.</p>
<blockquote>
<div><p>NOTE: <code class="docutils literal notranslate"><span class="pre">vfork()</span></code> is not an independent NuttX feature, but is
implemented in architecture-specific logic (using only helper
functions from the NuttX core logic). As a result, <code class="docutils literal notranslate"><span class="pre">vfork()</span></code> may
not be available on all architectures.</p>
</div></blockquote>
<dl class="field-list simple">
<dt class="field-odd">Returns<span class="colon">:</span></dt>
<dd class="field-odd"><p>Upon successful completion, <code class="docutils literal notranslate"><span class="pre">vfork()</span></code> returns 0 to
the child process and returns the process ID of the child process to the
parent process. Otherwise, -1 is returned to the parent, no child
process is created, and <code class="docutils literal notranslate"><span class="pre">errno</span></code> is set to indicate the error.</p>
</dd>
</dl>
<p><strong>POSIX Compatibility:</strong> Compatible with the BSD/Linux interface of the
same name. POSIX marks this interface as Obsolete.</p>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.exec">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">exec</span></span></span><span class="sig-paren">(</span><span class="pre">FAR</span><span class="w"> </span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">filename</span></span>, <span class="pre">FAR</span><span class="w"> </span><span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">argv</span></span>, <span class="pre">FAR</span><span class="w"> </span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="k"><span class="pre">struct</span></span><span class="w"> </span><span class="n"><span class="pre">symtab_s</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">exports</span></span>, <span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">nexports</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.exec" title="Permalink to this definition"></a><br /></dt>
<dd><p>This non-standard, NuttX function is similar to
<code class="docutils literal notranslate"><span class="pre">execv()</span></code> and <code class="docutils literal notranslate"><span class="pre">posix_spawn()</span></code> but differs in the following ways;</p>
<ul class="simple">
<li><p>Unlike <code class="docutils literal notranslate"><span class="pre">execv()</span></code> and <code class="docutils literal notranslate"><span class="pre">posix_spawn()</span></code> this function accepts symbol
table information as input parameters. This means that the symbol
table used to link the application prior to execution is provided by
the caller, not by the system.</p></li>
<li><p>Unlike <code class="docutils literal notranslate"><span class="pre">execv()</span></code>, this function always returns.</p></li>
</ul>
<p>This non-standard interface is included as a official NuttX API only
because it is needed in certain build modes: <code class="docutils literal notranslate"><span class="pre">exec()</span></code> is probably the
only want to load programs in the PROTECTED mode. Other file execution
APIs rely on a symbol table provided by the OS. In the PROTECTED build
mode, the OS cannot provide any meaningful symbolic information for
execution of code in the user-space blob so that is the <code class="docutils literal notranslate"><span class="pre">exec()</span></code>
function is really needed in that build case</p>
<p>The interface is available in the FLAT build mode although it is not
really necessary in that case. It is currently used by some example code
under the <code class="docutils literal notranslate"><span class="pre">apps/</span></code> that that generate their own symbol tables for
linking test programs. So although it is not necessary, it can still be
useful.</p>
<p>The interface would be completely useless and will not be supported in
the KERNEL build mode where the contrary is true: An application process
cannot provide any meaning symbolic information for use in linking a
different process.</p>
<p><strong>NOTE</strong>: This function is flawed and useless without
<code class="docutils literal notranslate"><span class="pre">CONFIG_SCHED_ONEXIT</span></code> and <code class="docutils literal notranslate"><span class="pre">CONFIG_SCHED_HAVE_PARENT</span></code> because without
those features there is then no mechanism to unload the module once it
exits.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters<span class="colon">:</span></dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>filename</strong> – The path to the program to be executed. If
<code class="docutils literal notranslate"><span class="pre">CONFIG_LIBC_ENVPATH</span></code> is defined in the configuration, then this may
be a relative path from the current working directory. Otherwise,
<code class="docutils literal notranslate"><span class="pre">path</span></code> must be the absolute path to the program.</p></li>
<li><p><strong>argv</strong> – A pointer to an array of string arguments. The end of the
array is indicated with a NULL entry.</p></li>
<li><p><strong>exports</strong> – The address of the start of the caller-provided symbol
table. This symbol table contains the addresses of symbols exported
by the caller and made available for linking the module into the
system.</p></li>
<li><p><strong>nexports</strong> – The number of symbols in the <code class="docutils literal notranslate"><span class="pre">exports</span></code> table.</p></li>
</ul>
</dd>
<dt class="field-even">Returns<span class="colon">:</span></dt>
<dd class="field-even"><p>Zero (OK) is returned on success; On any failure, <code class="docutils literal notranslate"><span class="pre">exec()</span></code>
will return -1 (<code class="docutils literal notranslate"><span class="pre">ERROR</span></code>) and will set the <code class="docutils literal notranslate"><span class="pre">errno</span></code> value
appropriately.</p>
</dd>
</dl>
<p><strong>POSIX Compatibility:</strong> This is a non-standard interface unique to
NuttX. Motivation for inclusion of this non-standard interface in
certain build modes is discussed above.</p>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.execv">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">execv</span></span></span><span class="sig-paren">(</span><span class="pre">FAR</span><span class="w"> </span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">path</span></span>, <span class="pre">FAR</span><span class="w"> </span><span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="n"><span class="pre">argv</span></span><span class="p"><span class="pre">[</span></span><span class="p"><span class="pre">]</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.execv" title="Permalink to this definition"></a><br /></dt>
<dd><p>The standard <code class="docutils literal notranslate"><span class="pre">exec</span></code> family of functions will replace
the current process image with a new process image. The new image will
be constructed from a regular, executable file called the new process
image file. There will be no return from a successful <code class="docutils literal notranslate"><span class="pre">exec</span></code>, because
the calling process image is overlaid by the new process image.</p>
<p>Simplified <code class="docutils literal notranslate"><span class="pre">execl()</span></code> and <code class="docutils literal notranslate"><span class="pre">execv()</span></code> functions are provided by NuttX
for compatibility. NuttX is a tiny embedded RTOS that does not support
processes and hence the concept of overlaying a tasks process image with
a new process image does not make any sense. In NuttX, these functions
are wrapper functions that:</p>
<blockquote>
<div><ol class="arabic simple">
<li><p>Call the non-standard <code class="docutils literal notranslate"><span class="pre">binfmt</span></code> function <code class="docutils literal notranslate"><span class="pre">exec()</span></code>, and then</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">exit(0)</span></code>.</p></li>
</ol>
</div></blockquote>
<p>Note the inefficiency when <code class="docutils literal notranslate"><span class="pre">execv()</span></code> or <code class="docutils literal notranslate"><span class="pre">execl()</span></code> is called in the
normal, two-step process: (1) first call <code class="docutils literal notranslate"><span class="pre">vfork()</span></code> to create a new
thread, then (2) call <code class="docutils literal notranslate"><span class="pre">execv()</span></code> or <code class="docutils literal notranslate"><span class="pre">execl()</span></code> to replace the new
thread with a program from the file system. Since the new thread will be
terminated by the <code class="docutils literal notranslate"><span class="pre">execv()</span></code> or <code class="docutils literal notranslate"><span class="pre">execl()</span></code> call, it really served no
purpose other than to support POSIX compatibility.</p>
<p>The non-standard binfmt function <code class="docutils literal notranslate"><span class="pre">exec()</span></code> needs to have (1) a symbol
table that provides the list of symbols exported by the base code, and
(2) the number of symbols in that table. This information is currently
provided to <code class="docutils literal notranslate"><span class="pre">exec()</span></code> from <code class="docutils literal notranslate"><span class="pre">execv()</span></code> or <code class="docutils literal notranslate"><span class="pre">execl()</span></code> via NuttX
configuration settings:</p>
<blockquote>
<div><ul class="simple">
<li><p><code class="docutils literal notranslate"><span class="pre">CONFIG_LIBC_EXECFUNCS</span></code>: Enable <code class="docutils literal notranslate"><span class="pre">execv()</span></code> and <code class="docutils literal notranslate"><span class="pre">execl()</span></code> support</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">CONFIG_EXECFUNCS_SYMTAB_ARRAY</span></code>: Name of the symbol table used by
<code class="docutils literal notranslate"><span class="pre">execv()</span></code> or <code class="docutils literal notranslate"><span class="pre">execl()</span></code>.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">CONFIG_EXECFUNCS_NSYMBOLS_VAR</span></code>: Name of the <code class="docutils literal notranslate"><span class="pre">int</span></code> variable
holding the number of symbols in the symbol table</p></li>
</ul>
</div></blockquote>
<p>As a result of the above, the current implementations of <code class="docutils literal notranslate"><span class="pre">execl()</span></code> and
<code class="docutils literal notranslate"><span class="pre">execv()</span></code> suffer from some incompatibilities that may or may not be
addressed in a future version of NuttX. Other than just being an
inefficient use of MCU resource, the most serious of these is that the
<code class="docutils literal notranslate"><span class="pre">exec</span></code>’ed task will not have the same task ID as the <code class="docutils literal notranslate"><span class="pre">vfork</span></code>’ed
function. So the parent function cannot know the ID of the <code class="docutils literal notranslate"><span class="pre">exec</span></code>’ed
task.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters<span class="colon">:</span></dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>path</strong> – The path to the program to be executed. If
<code class="docutils literal notranslate"><span class="pre">CONFIG_LIBC_ENVPATH</span></code> is defined in the configuration, then this may
be a relative path from the current working directory. Otherwise,</p></li>
<li><p><strong>path</strong> – must be the absolute path to the program.</p></li>
</ul>
</dd>
<dt class="field-even">Returns<span class="colon">:</span></dt>
<dd class="field-even"><p>This function does not return on success. On
failure, it will return -1 (<code class="docutils literal notranslate"><span class="pre">ERROR</span></code>) and will set the <code class="docutils literal notranslate"><span class="pre">errno</span></code> value
appropriately.</p>
</dd>
</dl>
<p><strong>POSIX Compatibility:</strong> Similar with the POSIX interface of the same
name. There are, however, several compatibility issues as detailed in
the description above.</p>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.execl">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">execl</span></span></span><span class="sig-paren">(</span><span class="pre">FAR</span><span class="w"> </span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">path</span></span>, <span class="p"><span class="pre">...</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.execl" title="Permalink to this definition"></a><br /></dt>
<dd><p><code class="docutils literal notranslate"><span class="pre">execl()</span></code> is functionally equivalent to
<a class="reference external" href="#execv">execv()</a>, differing only in the form of its input
parameters. See the description of <a class="reference external" href="#execv">execv()</a> for additional
information.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters<span class="colon">:</span></dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>path</strong> – The path to the program to be executed. If
<code class="docutils literal notranslate"><span class="pre">CONFIG_LIBC_ENVPATH</span></code> is defined in the configuration, then this may
be a relative path from the current working directory. Otherwise,</p></li>
<li><p><strong>path</strong> – must be the absolute path to the program.</p></li>
</ul>
</dd>
<dt class="field-even">Returns<span class="colon">:</span></dt>
<dd class="field-even"><p>This function does not return on success. On
failure, it will return -1 (<code class="docutils literal notranslate"><span class="pre">ERROR</span></code>) and will set the <code class="docutils literal notranslate"><span class="pre">errno</span></code> value
appropriately.</p>
</dd>
</dl>
<p><strong>POSIX Compatibility:</strong> Similar with the POSIX interface of the same
name. There are, however, several compatibility issues as detailed in
the description of <a class="reference external" href="#execv">execv()</a>.</p>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.posix_spawn">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">posix_spawn</span></span></span><span class="sig-paren">(</span><span class="pre">FAR</span><span class="w"> </span><a class="reference internal" href="structures.html#c.pid_t" title="pid_t"><span class="n"><span class="pre">pid_t</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">pid</span></span>, <span class="pre">FAR</span><span class="w"> </span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">path</span></span>, <span class="pre">FAR</span><span class="w"> </span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="n"><span class="pre">posix_spawn_file_actions_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">file_actions</span></span>, <span class="pre">FAR</span><span class="w"> </span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="n"><span class="pre">posix_spawnattr_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">attr</span></span>, <span class="pre">FAR</span><span class="w"> </span><span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="n"><span class="pre">argv</span></span><span class="p"><span class="pre">[</span></span><span class="p"><span class="pre">]</span></span>, <span class="pre">FAR</span><span class="w"> </span><span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="n"><span class="pre">envp</span></span><span class="p"><span class="pre">[</span></span><span class="p"><span class="pre">]</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.posix_spawn" title="Permalink to this definition"></a><br /></dt>
<dd></dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.posix_spawnp">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">posix_spawnp</span></span></span><span class="sig-paren">(</span><span class="pre">FAR</span><span class="w"> </span><a class="reference internal" href="structures.html#c.pid_t" title="pid_t"><span class="n"><span class="pre">pid_t</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">pid</span></span>, <span class="pre">FAR</span><span class="w"> </span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">file</span></span>, <span class="pre">FAR</span><span class="w"> </span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="n"><span class="pre">posix_spawn_file_actions_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">file_actions</span></span>, <span class="pre">FAR</span><span class="w"> </span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="n"><span class="pre">posix_spawnattr_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">attr</span></span>, <span class="pre">FAR</span><span class="w"> </span><span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="n"><span class="pre">argv</span></span><span class="p"><span class="pre">[</span></span><span class="p"><span class="pre">]</span></span>, <span class="pre">FAR</span><span class="w"> </span><span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="n"><span class="pre">envp</span></span><span class="p"><span class="pre">[</span></span><span class="p"><span class="pre">]</span></span><span class="sig-paren">)</span><span class="p"><span class="pre">;</span></span><a class="headerlink" href="#c.posix_spawnp" title="Permalink to this definition"></a><br /></dt>
<dd><p>The <code class="docutils literal notranslate"><span class="pre">posix_spawn()</span></code> and <code class="docutils literal notranslate"><span class="pre">posix_spawnp()</span></code> functions
will create a new, child task, constructed from a regular executable
file.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters<span class="colon">:</span></dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>pid</strong> – Upon successful completion, <code class="docutils literal notranslate"><span class="pre">posix_spawn()</span></code> and
<code class="docutils literal notranslate"><span class="pre">posix_spawnp()</span></code> will return the task ID of the child task to the
parent task, in the variable pointed to by a non-NULL <code class="docutils literal notranslate"><span class="pre">pid</span></code>
argument. If the <code class="docutils literal notranslate"><span class="pre">pid</span></code> argument is a null pointer, the process ID
of the child is not returned to the caller.</p></li>
<li><p><strong>path</strong> – <p>The <code class="docutils literal notranslate"><span class="pre">path</span></code> argument to <code class="docutils literal notranslate"><span class="pre">posix_spawn()</span></code> is
the absolute path that identifies the file to execute. The <code class="docutils literal notranslate"><span class="pre">file</span></code>
argument to <code class="docutils literal notranslate"><span class="pre">posix_spawnp()</span></code> may also be a relative path and will
be used to construct a pathname that identifies the file to execute.
In the case of a relative path, the path prefix for the file will be
obtained by a search of the directories passed as the environment
variable PATH.</p>
<p>NOTE: NuttX provides only one implementation: If
<code class="docutils literal notranslate"><span class="pre">CONFIG_LIBC_ENVPATH</span></code> is defined, then only <code class="docutils literal notranslate"><span class="pre">posix_spawnp()</span></code>
behavior is supported; otherwise, only <code class="docutils literal notranslate"><span class="pre">posix_spawn</span></code> behavior is
supported.</p>
</p></li>
<li><p><strong>file_actions</strong> – If <code class="docutils literal notranslate"><span class="pre">file_actions</span></code> is a null pointer, then file
descriptors open in the calling process will remain open in the child
process (unless <code class="docutils literal notranslate"><span class="pre">CONFIG_FDCLONE_STDIO</span></code> is defined). If
<code class="docutils literal notranslate"><span class="pre">file_actions</span></code> is not NULL, then the file descriptors open in the
child process will be those open in the calling process as modified
by the spawn file actions object pointed to by <code class="docutils literal notranslate"><span class="pre">file_actions</span></code>.</p></li>
<li><p><strong>attr</strong> – <p>If the value of the <code class="docutils literal notranslate"><span class="pre">attr</span></code> parameter is <code class="docutils literal notranslate"><span class="pre">NULL</span></code>, the all
default values for the POSIX spawn attributes will be used.
Otherwise, the attributes will be set according to the spawn flags.
The <code class="docutils literal notranslate"><span class="pre">posix_spawnattr_t</span></code> spawn attributes object type is defined in
<code class="docutils literal notranslate"><span class="pre">spawn.h</span></code>. It will contains these attributes, not all of which are
supported by NuttX:</p>
<ul>
<li><p><code class="docutils literal notranslate"><span class="pre">POSIX_SPAWN_SETPGROUP</span></code>: Setting of the new task’s process group
is not supported. NuttX does not support process groups.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">POSIX_SPAWN_SETSCHEDPARAM</span></code>: Set new tasks priority to the
<code class="docutils literal notranslate"><span class="pre">sched_param</span></code> value.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">POSIX_SPAWN_SETSCHEDULER</span></code>: Set the new task’s scheduler policy
to the <code class="docutils literal notranslate"><span class="pre">sched_policy</span></code> value.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">POSIX_SPAWN_RESETIDS</span></code> Resetting of the effective user ID of the
child process is not supported. NuttX does not support effective
user IDs.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">POSIX_SPAWN_SETSIGMASK</span></code>: Set the new task’s signal mask.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">POSIX_SPAWN_SETSIGDEF</span></code>: Resetting signal default actions is not
supported. NuttX does not support default signal actions.</p></li>
</ul>
</p></li>
<li><p><strong>argv</strong> – <code class="docutils literal notranslate"><span class="pre">argv[]</span></code> is the argument list for the new task.
<code class="docutils literal notranslate"><span class="pre">argv[]</span></code> is an array of pointers to null-terminated strings. The
list is terminated with a null pointer.</p></li>
<li><p><strong>envp</strong> – The <code class="docutils literal notranslate"><span class="pre">envp[]</span></code> argument is not used by NuttX and may be
<code class="docutils literal notranslate"><span class="pre">NULL</span></code>. In standard implementations, <code class="docutils literal notranslate"><span class="pre">envp[]</span></code> is an array of
character pointers to null-terminated strings that provide the
environment for the new process image. The environment array is
terminated by a null pointer. In NuttX, the <code class="docutils literal notranslate"><span class="pre">envp[]</span></code> argument is
ignored and the new task will inherit the environment of the parent
task unconditionally.</p></li>
</ul>
</dd>
<dt class="field-even">Returns<span class="colon">:</span></dt>
<dd class="field-even"><p><p>Zero on success. Otherwise, an error number will be returned as the
function return value to indicate the error:</p>
<ul class="simple">
<li><p><code class="docutils literal notranslate"><span class="pre">EINVAL</span></code>: The value specified by <code class="docutils literal notranslate"><span class="pre">file_actions</span></code> or <code class="docutils literal notranslate"><span class="pre">attr</span></code> is
invalid.</p></li>
<li><p>Any errors that might have been return if <code class="docutils literal notranslate"><span class="pre">vfork()</span></code> and
<code class="docutils literal notranslate"><span class="pre">exec[l|v]()</span></code> had been called.</p></li>
</ul>
</p>
</dd>
</dl>
<p><strong>Assumptions/Limitations:</strong></p>
<ul class="simple">
<li><p>NuttX provides only <code class="docutils literal notranslate"><span class="pre">posix_spawn()</span></code> or <code class="docutils literal notranslate"><span class="pre">posix_spawnp()</span></code> behavior
depending upon the setting of <code class="docutils literal notranslate"><span class="pre">CONFIG_LIBC_ENVPATH</span></code>: If
<code class="docutils literal notranslate"><span class="pre">CONFIG_LIBC_ENVPATH</span></code> is defined, then only <code class="docutils literal notranslate"><span class="pre">posix_spawnp()</span></code>
behavior is supported; otherwise, only <code class="docutils literal notranslate"><span class="pre">posix_spawn()</span></code> behavior is
supported.</p></li>
<li><p>The <code class="docutils literal notranslate"><span class="pre">envp</span></code> argument is not used and the <code class="docutils literal notranslate"><span class="pre">environ</span></code> variable is not
altered (NuttX does not support the <code class="docutils literal notranslate"><span class="pre">environ</span></code> variable).</p></li>
<li><p>Process groups are not supported (See <code class="docutils literal notranslate"><span class="pre">POSIX_SPAWN_SETPGROUP</span></code>
above).</p></li>
<li><p>Effective user IDs are not supported (See <code class="docutils literal notranslate"><span class="pre">POSIX_SPAWN_RESETIDS</span></code>
above).</p></li>
<li><p>Signal default actions cannot be modified in the newly task executed
because NuttX does not support default signal actions (See
<code class="docutils literal notranslate"><span class="pre">POSIX_SPAWN_SETSIGDEF</span></code>).</p></li>
</ul>
<p><strong>POSIX Compatibility:</strong> The value of the <code class="docutils literal notranslate"><span class="pre">argv[0]</span></code> received by the
child task is assigned by NuttX. For the caller of <code class="docutils literal notranslate"><span class="pre">posix_spawn()</span></code>,
the provided argv[0] will correspond to <code class="docutils literal notranslate"><span class="pre">argv[1]</span></code> received by the new
task.</p>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.posix_spawn_file_actions_init">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">posix_spawn_file_actions_init</span></span></span><span class="sig-paren">(</span><span class="pre">FAR</span><span class="w"> </span><span class="n"><span class="pre">posix_spawn_file_actions_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">file_actions</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.posix_spawn_file_actions_init" title="Permalink to this definition"></a><br /></dt>
<dd><p>Initializes the object referenced by <code class="docutils literal notranslate"><span class="pre">file_actions</span></code> to an empty set of
file actions for subsequent use in a call to <code class="docutils literal notranslate"><span class="pre">posix_spawn()</span></code> or
<code class="docutils literal notranslate"><span class="pre">posix_spawnp()</span></code>.</p>
<p><strong>Input Parameters:</strong></p>
<ul class="simple">
<li><p><code class="docutils literal notranslate"><span class="pre">file_actions</span></code>: The address of the <code class="docutils literal notranslate"><span class="pre">posix_spawn_file_actions_t</span></code>
to be initialized.</p></li>
</ul>
<p><strong>Returned Value:</strong> On success, this function returns 0; on failure it
will return an error number from <code class="docutils literal notranslate"><span class="pre">&lt;errno.h&gt;</span></code>.</p>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.posix_spawn_file_actions_destroy">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">posix_spawn_file_actions_destroy</span></span></span><span class="sig-paren">(</span><span class="pre">FAR</span><span class="w"> </span><span class="n"><span class="pre">posix_spawn_file_actions_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">file_actions</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.posix_spawn_file_actions_destroy" title="Permalink to this definition"></a><br /></dt>
<dd><p>Destroys the object referenced by <code class="docutils literal notranslate"><span class="pre">file_actions</span></code> which was previously
initialized by <code class="docutils literal notranslate"><span class="pre">posix_spawn_file_actions_init()</span></code>, returning any
resources obtained at the time of initialization to the system for
subsequent reuse. A <code class="docutils literal notranslate"><span class="pre">posix_spawn_file_actions_t</span></code> may be reinitialized
after having been destroyed, but must not be reused after destruction,
unless it has been reinitialized.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters<span class="colon">:</span></dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>file_actions</strong> – The address of the <code class="docutils literal notranslate"><span class="pre">posix_spawn_file_actions_t</span></code>
to be destroyed.</p></li>
</ul>
</dd>
<dt class="field-even">Returns<span class="colon">:</span></dt>
<dd class="field-even"><p>On success, this function returns 0; on failure it
will return an error number from <code class="docutils literal notranslate"><span class="pre">&lt;errno.h&gt;</span></code></p>
</dd>
</dl>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.posix_spawn_file_actions_addclose">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">posix_spawn_file_actions_addclose</span></span></span><span class="sig-paren">(</span><span class="pre">FAR</span><span class="w"> </span><span class="n"><span class="pre">posix_spawn_file_actions_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">file_actions</span></span>, <span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">fd</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.posix_spawn_file_actions_addclose" title="Permalink to this definition"></a><br /></dt>
<dd><p>Adds a <em>close</em> operation to the list of operations associated with the
object referenced by <code class="docutils literal notranslate"><span class="pre">file_actions</span></code>, for subsequent use in a call to
<code class="docutils literal notranslate"><span class="pre">posix_spawn()</span></code> or <code class="docutils literal notranslate"><span class="pre">posix_spawnp()</span></code>. The descriptor referred to by
<code class="docutils literal notranslate"><span class="pre">fd</span></code> is closed as if <code class="docutils literal notranslate"><span class="pre">close()</span></code> had been called on it prior to the
new child process starting execution.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters<span class="colon">:</span></dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>file_actions</strong> – The address of the <code class="docutils literal notranslate"><span class="pre">posix_spawn_file_actions_t</span></code>
object to which the <em>close</em> operation will be appended.</p></li>
<li><p><strong>fd</strong> – The file descriptor to be closed.</p></li>
</ul>
</dd>
<dt class="field-even">Returns<span class="colon">:</span></dt>
<dd class="field-even"><p>On success, this function returns 0; on failure it
will return an error number from <code class="docutils literal notranslate"><span class="pre">&lt;errno.h&gt;</span></code></p>
</dd>
</dl>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.posix_spawn_file_actions_adddup2">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">posix_spawn_file_actions_adddup2</span></span></span><span class="sig-paren">(</span><span class="pre">FAR</span><span class="w"> </span><span class="n"><span class="pre">posix_spawn_file_actions_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">file_actions</span></span>, <span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">fd1</span></span>, <span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">fd2</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.posix_spawn_file_actions_adddup2" title="Permalink to this definition"></a><br /></dt>
<dd><p>Adds a <em>dup2</em> operation to the list of operations associated with the
object referenced by <code class="docutils literal notranslate"><span class="pre">file_actions</span></code>, for subsequent use in a call to
<code class="docutils literal notranslate"><span class="pre">posix_spawn()</span></code> or <code class="docutils literal notranslate"><span class="pre">posix_spawnp()</span></code>. The descriptor referred to by
<code class="docutils literal notranslate"><span class="pre">fd2</span></code> is created as if <code class="docutils literal notranslate"><span class="pre">dup2()</span></code> had been called on <code class="docutils literal notranslate"><span class="pre">fd1</span></code> prior to
the new child process starting execution.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters<span class="colon">:</span></dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>file_actions</strong> – The address of the <code class="docutils literal notranslate"><span class="pre">posix_spawn_file_actions_t</span></code>
object to which the <em>dup2</em> operation will be appended.</p></li>
<li><p><strong>fd1</strong> – The file descriptor to be be duplicated. The first file
descriptor to be argument to <code class="docutils literal notranslate"><span class="pre">dup2()</span></code>.</p></li>
<li><p><strong>fd2</strong> – The file descriptor to be be created. The second file
descriptor to be argument to <code class="docutils literal notranslate"><span class="pre">dup2()</span></code>.</p></li>
</ul>
</dd>
<dt class="field-even">Returns<span class="colon">:</span></dt>
<dd class="field-even"><p>On success, this function returns 0; on failure it
will return an error number from <code class="docutils literal notranslate"><span class="pre">&lt;errno.h&gt;</span></code></p>
</dd>
</dl>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.posix_spawn_file_actions_addopen">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">posix_spawn_file_actions_addopen</span></span></span><span class="sig-paren">(</span><span class="pre">FAR</span><span class="w"> </span><span class="n"><span class="pre">posix_spawn_file_actions_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">file_actions</span></span>, <span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">fd</span></span>, <span class="pre">FAR</span><span class="w"> </span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">path</span></span>, <span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">oflags</span></span>, <span class="n"><span class="pre">mode_t</span></span><span class="w"> </span><span class="n"><span class="pre">mode</span></span><span class="sig-paren">)</span><span class="p"><span class="pre">;</span></span><a class="headerlink" href="#c.posix_spawn_file_actions_addopen" title="Permalink to this definition"></a><br /></dt>
<dd><p>Adds an <em>open</em> operation to the list of operations associated with the
object referenced by <code class="docutils literal notranslate"><span class="pre">file_actions</span></code>, for subsequent use in a call to
<code class="docutils literal notranslate"><span class="pre">posix_spawn()</span></code> or <code class="docutils literal notranslate"><span class="pre">posix_spawnp()</span></code>. The descriptor referred to by
<code class="docutils literal notranslate"><span class="pre">fd</span></code> is opened using the <code class="docutils literal notranslate"><span class="pre">path</span></code>, <code class="docutils literal notranslate"><span class="pre">oflag</span></code>, and <code class="docutils literal notranslate"><span class="pre">mode</span></code> arguments
as if <code class="docutils literal notranslate"><span class="pre">open()</span></code> had been called on it prior to the new child process
starting execution. The string path is copied by the
<code class="docutils literal notranslate"><span class="pre">posix_spawn_file_actions_addopen()</span></code> function during this process, so
storage need not be persistent in the caller.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters<span class="colon">:</span></dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>file_actions</strong> – The address of the <code class="docutils literal notranslate"><span class="pre">posix_spawn_file_actions_t</span></code>
object to which the <em>open</em> operation will be appended.</p></li>
<li><p><strong>fd</strong> – The file descriptor to be opened.</p></li>
<li><p><strong>path</strong> – The path to be opened.</p></li>
<li><p><strong>oflags</strong> – Open flags.</p></li>
<li><p><strong>mode</strong> – File creation mode/</p></li>
</ul>
</dd>
<dt class="field-even">Returns<span class="colon">:</span></dt>
<dd class="field-even"><p>On success, this function returns 0; on failure it
will return an error number from <code class="docutils literal notranslate"><span class="pre">&lt;errno.h&gt;</span></code></p>
</dd>
</dl>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.posix_spawnattr_init">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">posix_spawnattr_init</span></span></span><span class="sig-paren">(</span><span class="pre">FAR</span><span class="w"> </span><span class="n"><span class="pre">posix_spawnattr_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">attr</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.posix_spawnattr_init" title="Permalink to this definition"></a><br /></dt>
<dd><p>The <code class="docutils literal notranslate"><span class="pre">posix_spawnattr_init()</span></code> function initializes the
object referenced by <code class="docutils literal notranslate"><span class="pre">attr</span></code>, to an empty set of spawn attributes for
subsequent use in a call to <code class="docutils literal notranslate"><span class="pre">posix_spawn()</span></code> or <code class="docutils literal notranslate"><span class="pre">posix_spawnp()</span></code>.</p>
<p>Then the spawn attributes are no longer needed, they should be destroyed
by calling <code class="docutils literal notranslate"><span class="pre">posix_spawnattr_destroyed()</span></code>. In NuttX, however,
<code class="docutils literal notranslate"><span class="pre">posix_spawnattr_destroyed()</span></code> is just stub:</p>
<p>For portability, the convention of calling
<code class="docutils literal notranslate"><span class="pre">posix_spawnattr_destroyed()</span></code> when the attributes are not longer
needed should still be followed.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters<span class="colon">:</span></dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>attr</strong> – The address of the spawn attributes to be initialized.</p></li>
</ul>
</dd>
<dt class="field-even">Returns<span class="colon">:</span></dt>
<dd class="field-even"><p>On success, this function returns 0; on failure it
will return an error number from <code class="docutils literal notranslate"><span class="pre">&lt;errno.h&gt;</span></code></p>
</dd>
</dl>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.posix_spawnattr_getflags">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">posix_spawnattr_getflags</span></span></span><span class="sig-paren">(</span><span class="pre">FAR</span><span class="w"> </span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="n"><span class="pre">posix_spawnattr_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">attr</span></span>, <span class="pre">FAR</span><span class="w"> </span><span class="kt"><span class="pre">short</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">flags</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.posix_spawnattr_getflags" title="Permalink to this definition"></a><br /></dt>
<dd><p>The <code class="docutils literal notranslate"><span class="pre">posix_spawnattr_getflags()</span></code> function will obtain
the value of the <em>spawn-flags</em> attribute from the attributes object
referenced by <code class="docutils literal notranslate"><span class="pre">attr</span></code>.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters<span class="colon">:</span></dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>attr</strong> – The address spawn attributes to be queried.</p></li>
<li><p><strong>flags</strong> – The location to return the spawn flags</p></li>
</ul>
</dd>
<dt class="field-even">Returns<span class="colon">:</span></dt>
<dd class="field-even"><p>On success, this function returns 0; on failure it
will return an error number from <code class="docutils literal notranslate"><span class="pre">&lt;errno.h&gt;</span></code></p>
</dd>
</dl>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.posix_spawnattr_getschedparam">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">posix_spawnattr_getschedparam</span></span></span><span class="sig-paren">(</span><span class="pre">FAR</span><span class="w"> </span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="n"><span class="pre">posix_spawnattr_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">attr</span></span>, <span class="pre">FAR</span><span class="w"> </span><span class="k"><span class="pre">struct</span></span><span class="w"> </span><a class="reference internal" href="structures.html#c.sched_param" title="sched_param"><span class="n"><span class="pre">sched_param</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">param</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.posix_spawnattr_getschedparam" title="Permalink to this definition"></a><br /></dt>
<dd><p>The <code class="docutils literal notranslate"><span class="pre">posix_spawnattr_getschedparam()</span></code> function will
obtain the value of the <em>spawn-schedparam</em> attribute from the attributes
object referenced by <code class="docutils literal notranslate"><span class="pre">attr</span></code>.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters<span class="colon">:</span></dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>attr</strong> – The address spawn attributes to be queried.</p></li>
<li><p><strong>param</strong> – The location to return the <em>spawn-schedparam</em> value.</p></li>
</ul>
</dd>
<dt class="field-even">Returns<span class="colon">:</span></dt>
<dd class="field-even"><p>On success, this function returns 0; on failure it
will return an error number from <code class="docutils literal notranslate"><span class="pre">&lt;errno.h&gt;</span></code></p>
</dd>
</dl>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.posix_spawnattr_getschedpolicy">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">posix_spawnattr_getschedpolicy</span></span></span><span class="sig-paren">(</span><span class="pre">FAR</span><span class="w"> </span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="n"><span class="pre">posix_spawnattr_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">attr</span></span>, <span class="pre">FAR</span><span class="w"> </span><span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">policy</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.posix_spawnattr_getschedpolicy" title="Permalink to this definition"></a><br /></dt>
<dd><p>The <code class="docutils literal notranslate"><span class="pre">posix_spawnattr_getschedpolicy()</span></code> function will
obtain the value of the <em>spawn-schedpolicy</em> attribute from the
attributes object referenced by <code class="docutils literal notranslate"><span class="pre">attr</span></code>.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters<span class="colon">:</span></dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>attr</strong> – The address spawn attributes to be queried.</p></li>
<li><p><strong>policy</strong> – The location to return the <em>spawn-schedpolicy</em> value.</p></li>
</ul>
</dd>
<dt class="field-even">Returns<span class="colon">:</span></dt>
<dd class="field-even"><p>On success, this function returns 0; on failure it
will return an error number from <code class="docutils literal notranslate"><span class="pre">&lt;errno.h&gt;</span></code></p>
</dd>
</dl>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.posix_spawnattr_getsigmask">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">posix_spawnattr_getsigmask</span></span></span><span class="sig-paren">(</span><span class="pre">FAR</span><span class="w"> </span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="n"><span class="pre">posix_spawnattr_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">attr</span></span>, <span class="pre">FAR</span><span class="w"> </span><a class="reference internal" href="structures.html#c.sigset_t" title="sigset_t"><span class="n"><span class="pre">sigset_t</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">sigmask</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.posix_spawnattr_getsigmask" title="Permalink to this definition"></a><br /></dt>
<dd><p><code class="docutils literal notranslate"><span class="pre">posix_spawnattr_getsigdefault()</span></code> function will
obtain the value of the <em>spawn-sigmask</em> attribute from the attributes
object referenced by <code class="docutils literal notranslate"><span class="pre">attr</span></code>.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters<span class="colon">:</span></dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>attr</strong> – The address spawn attributes to be queried.</p></li>
<li><p><strong>sigmask</strong> – The location to return the <em>spawn-sigmask</em> value.</p></li>
</ul>
</dd>
<dt class="field-even">Returns<span class="colon">:</span></dt>
<dd class="field-even"><p>On success, this function returns 0; on failure it
will return an error number from <code class="docutils literal notranslate"><span class="pre">&lt;errno.h&gt;</span></code></p>
</dd>
</dl>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.posix_spawnattr_setflags">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">posix_spawnattr_setflags</span></span></span><span class="sig-paren">(</span><span class="pre">FAR</span><span class="w"> </span><span class="n"><span class="pre">posix_spawnattr_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">attr</span></span>, <span class="kt"><span class="pre">short</span></span><span class="w"> </span><span class="n"><span class="pre">flags</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.posix_spawnattr_setflags" title="Permalink to this definition"></a><br /></dt>
<dd><p>The <code class="docutils literal notranslate"><span class="pre">posix_spawnattr_setflags()</span></code> function will set
the <em>spawn-flags</em> attribute in an initialized attributes object
referenced by <code class="docutils literal notranslate"><span class="pre">attr</span></code>.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters<span class="colon">:</span></dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>attr</strong> – The address spawn attributes to be used.</p></li>
<li><p><strong>flags</strong> – The new value of the <em>spawn-flags</em> attribute.</p></li>
</ul>
</dd>
<dt class="field-even">Returns<span class="colon">:</span></dt>
<dd class="field-even"><p>On success, this function returns 0; on failure it
will return an error number from <code class="docutils literal notranslate"><span class="pre">&lt;errno.h&gt;</span></code></p>
</dd>
</dl>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.posix_spawnattr_setschedparam">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">posix_spawnattr_setschedparam</span></span></span><span class="sig-paren">(</span><span class="pre">FAR</span><span class="w"> </span><span class="n"><span class="pre">posix_spawnattr_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">attr</span></span>, <span class="pre">FAR</span><span class="w"> </span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="k"><span class="pre">struct</span></span><span class="w"> </span><a class="reference internal" href="structures.html#c.sched_param" title="sched_param"><span class="n"><span class="pre">sched_param</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">param</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.posix_spawnattr_setschedparam" title="Permalink to this definition"></a><br /></dt>
<dd><p>The <code class="docutils literal notranslate"><span class="pre">posix_spawnattr_setschedparam()</span></code> function will
set the <em>spawn-schedparam</em> attribute in an initialized attributes object
referenced by <code class="docutils literal notranslate"><span class="pre">attr</span></code>.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters<span class="colon">:</span></dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>attr</strong> – The address spawn attributes to be used.</p></li>
<li><p><strong>param</strong> – The new value of the <em>spawn-schedparam</em> attribute.</p></li>
</ul>
</dd>
<dt class="field-even">Returns<span class="colon">:</span></dt>
<dd class="field-even"><p>On success, this function returns 0; on failure it
will return an error number from <code class="docutils literal notranslate"><span class="pre">&lt;errno.h&gt;</span></code></p>
</dd>
</dl>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.posix_spawnattr_setschedpolicy">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">posix_spawnattr_setschedpolicy</span></span></span><span class="sig-paren">(</span><span class="pre">FAR</span><span class="w"> </span><span class="n"><span class="pre">posix_spawnattr_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">attr</span></span>, <span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">policy</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.posix_spawnattr_setschedpolicy" title="Permalink to this definition"></a><br /></dt>
<dd><p>The <code class="docutils literal notranslate"><span class="pre">posix_spawnattr_setschedpolicy()</span></code> function will
set the <em>spawn-schedpolicy</em> attribute in an initialized attributes
object referenced by <code class="docutils literal notranslate"><span class="pre">attr</span></code>.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters<span class="colon">:</span></dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>attr</strong> – The address spawn attributes to be used.</p></li>
<li><p><strong>policy</strong> – The new value of the <em>spawn-schedpolicy</em> attribute.</p></li>
</ul>
</dd>
<dt class="field-even">Returns<span class="colon">:</span></dt>
<dd class="field-even"><p>On success, this function returns 0; on failure it
will return an error number from <code class="docutils literal notranslate"><span class="pre">&lt;errno.h&gt;</span></code></p>
</dd>
</dl>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.posix_spawnattr_setsigmask">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">posix_spawnattr_setsigmask</span></span></span><span class="sig-paren">(</span><span class="pre">FAR</span><span class="w"> </span><span class="n"><span class="pre">posix_spawnattr_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">attr</span></span>, <span class="pre">FAR</span><span class="w"> </span><span class="k"><span class="pre">const</span></span><span class="w"> </span><a class="reference internal" href="structures.html#c.sigset_t" title="sigset_t"><span class="n"><span class="pre">sigset_t</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">sigmask</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.posix_spawnattr_setsigmask" title="Permalink to this definition"></a><br /></dt>
<dd><p>The <code class="docutils literal notranslate"><span class="pre">posix_spawnattr_setsigmask()</span></code> function will set
the <em>spawn-sigmask</em> attribute in an initialized attributes object
referenced by <code class="docutils literal notranslate"><span class="pre">attr</span></code>.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters<span class="colon">:</span></dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>attr</strong> – The address spawn attributes to be used.</p></li>
<li><p><strong>sigmask</strong> – The new value of the <em>spawn-sigmask</em> attribute.</p></li>
</ul>
</dd>
<dt class="field-even">Returns<span class="colon">:</span></dt>
<dd class="field-even"><p>On success, this function returns 0; on failure it
will return an error number from <code class="docutils literal notranslate"><span class="pre">&lt;errno.h&gt;</span></code></p>
</dd>
</dl>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.task_spawn">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">task_spawn</span></span></span><span class="sig-paren">(</span><span class="pre">FAR</span><span class="w"> </span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">name</span></span>, <a class="reference internal" href="structures.html#c.main_t" title="main_t"><span class="n"><span class="pre">main_t</span></span></a><span class="w"> </span><span class="n"><span class="pre">entry</span></span>, <span class="pre">FAR</span><span class="w"> </span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="n"><span class="pre">posix_spawn_file_actions_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">file_actions</span></span>, <span class="pre">FAR</span><span class="w"> </span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="n"><span class="pre">posix_spawnattr_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">attr</span></span>, <span class="pre">FAR</span><span class="w"> </span><span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="n"><span class="pre">argv</span></span><span class="p"><span class="pre">[</span></span><span class="p"><span class="pre">]</span></span>, <span class="pre">FAR</span><span class="w"> </span><span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="n"><span class="pre">envp</span></span><span class="p"><span class="pre">[</span></span><span class="p"><span class="pre">]</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.task_spawn" title="Permalink to this definition"></a><br /></dt>
<dd><p>The <code class="docutils literal notranslate"><span class="pre">task_spawn()</span></code> function will create a new, child
task, where the entry point to the task is an address in memory.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters<span class="colon">:</span></dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>name</strong> – The name to assign to the child task.</p></li>
<li><p><strong>entry</strong> – The child task’s entry point (an address in memory).</p></li>
<li><p><strong>file_actions</strong> – If <code class="docutils literal notranslate"><span class="pre">file_actions</span></code> is a null pointer, then file
descriptors open in the calling process will remain open in the child
process (unless <code class="docutils literal notranslate"><span class="pre">CONFIG_FDCLONE_STDIO</span></code> is defined). If
<code class="docutils literal notranslate"><span class="pre">file_actions</span></code> is not NULL, then the file descriptors open in the
child process will be those open in the calling process as modified
by the spawn file actions object pointed to by <code class="docutils literal notranslate"><span class="pre">file_actions</span></code>.</p></li>
<li><p><strong>attr</strong> – <p>If the value of the <code class="docutils literal notranslate"><span class="pre">attr</span></code> parameter is <code class="docutils literal notranslate"><span class="pre">NULL</span></code>, the all
default values for the POSIX spawn attributes will be used.
Otherwise, the attributes will be set according to the spawn flags.
The <code class="docutils literal notranslate"><span class="pre">posix_spawnattr_t</span></code> spawn attributes object type is defined in
<code class="docutils literal notranslate"><span class="pre">spawn.h</span></code>. It will contains these attributes, not all of which are
supported by NuttX:</p>
<ul>
<li><p><code class="docutils literal notranslate"><span class="pre">POSIX_SPAWN_SETPGROUP</span></code>: Setting of the new task’s process group
is not supported. NuttX does not support process groups.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">POSIX_SPAWN_SETSCHEDPARAM</span></code>: Set new tasks priority to the
<code class="docutils literal notranslate"><span class="pre">sched_param</span></code> value.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">POSIX_SPAWN_SETSCHEDULER</span></code>: Set the new task’s scheduler policy
to the <code class="docutils literal notranslate"><span class="pre">sched_policy</span></code> value.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">POSIX_SPAWN_RESETIDS</span></code> Resetting of the effective user ID of the
child process is not supported. NuttX does not support effective
user IDs.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">POSIX_SPAWN_SETSIGMASK</span></code>: Set the new task’s signal mask.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">POSIX_SPAWN_SETSIGDEF</span></code>: Resetting signal default actions is not
supported. NuttX does not support default signal actions.</p></li>
</ul>
<p>And the non-standard:</p>
<ul>
<li><p><code class="docutils literal notranslate"><span class="pre">TASK_SPAWN_SETSTACKSIZE</span></code>: Set the stack size for the new task.</p></li>
</ul>
</p></li>
<li><p><strong>argv</strong> – <code class="docutils literal notranslate"><span class="pre">argv[]</span></code> is the argument list for the new task.
<code class="docutils literal notranslate"><span class="pre">argv[]</span></code> is an array of pointers to null-terminated strings. The
list is terminated with a null pointer.</p></li>
<li><p><strong>envp</strong> – The <code class="docutils literal notranslate"><span class="pre">envp[]</span></code> argument is not used by NuttX and may be
<code class="docutils literal notranslate"><span class="pre">NULL</span></code>.</p></li>
</ul>
</dd>
<dt class="field-even">Returns<span class="colon">:</span></dt>
<dd class="field-even"><p><code class="docutils literal notranslate"><span class="pre">task_spawn()</span></code> will return process ID of new task on success.
Otherwise, a negative number will be returned as the function return
value to indicate the error:</p>
</dd>
</dl>
<p><strong>POSIX Compatibility:</strong> This is a non-standard interface inspired by
<code class="docutils literal notranslate"><span class="pre">posix_spawn()</span></code>.</p>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.posix_spawnattr_getstacksize">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">posix_spawnattr_getstacksize</span></span></span><span class="sig-paren">(</span><span class="pre">FAR</span><span class="w"> </span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="n"><span class="pre">posix_spawnattr_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">attr</span></span>, <span class="pre">FAR</span><span class="w"> </span><a class="reference internal" href="structures.html#c.size_t" title="size_t"><span class="n"><span class="pre">size_t</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">stacksize</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.posix_spawnattr_getstacksize" title="Permalink to this definition"></a><br /></dt>
<dd><p>The <code class="docutils literal notranslate"><span class="pre">posix_spawnattr_getstacksize()</span></code> function will
obtain the value of the <em>spawn-stacksize</em> attribute from the attributes
object referenced by <code class="docutils literal notranslate"><span class="pre">attr</span></code>.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters<span class="colon">:</span></dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>attr</strong> – The address spawn attributes to be queried.</p></li>
<li><p><strong>policy</strong> – The location to return the <em>spawn-stacksize</em> value.</p></li>
</ul>
</dd>
<dt class="field-even">Returns<span class="colon">:</span></dt>
<dd class="field-even"><p>On success, this function returns 0; on failure it
will return an error number from <code class="docutils literal notranslate"><span class="pre">&lt;errno.h&gt;</span></code></p>
</dd>
</dl>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.posix_spawnattr_setstacksize">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">posix_spawnattr_setstacksize</span></span></span><span class="sig-paren">(</span><span class="pre">FAR</span><span class="w"> </span><span class="n"><span class="pre">posix_spawnattr_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">attr</span></span>, <a class="reference internal" href="structures.html#c.size_t" title="size_t"><span class="n"><span class="pre">size_t</span></span></a><span class="w"> </span><span class="n"><span class="pre">stacksize</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.posix_spawnattr_setstacksize" title="Permalink to this definition"></a><br /></dt>
<dd><p>The <code class="docutils literal notranslate"><span class="pre">posix_spawnattr_setstacksize()</span></code> function will set
the <em>spawn-stacksize</em> attribute in an initialized attributes object
referenced by <code class="docutils literal notranslate"><span class="pre">attr</span></code>.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters<span class="colon">:</span></dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>attr</strong> – The address spawn attributes to be used.</p></li>
<li><p><strong>policy</strong> – The new value of the <em>spawn-stacksize</em> attribute.</p></li>
</ul>
</dd>
<dt class="field-even">Returns<span class="colon">:</span></dt>
<dd class="field-even"><p>On success, this function returns 0; on failure it
will return an error number from <code class="docutils literal notranslate"><span class="pre">&lt;errno.h&gt;</span></code></p>
</dd>
</dl>
</dd></dl>

</section>
</section>


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