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<li><a class="reference internal" href="#">trap - perform an action when the shell receives a signal</a><ul>
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<section id="trap-perform-an-action-when-the-shell-receives-a-signal">
<h1>trap - perform an action when the shell receives a signal<a class="headerlink" href="#trap-perform-an-action-when-the-shell-receives-a-signal" title="Link to this heading">¶</a></h1>
<section id="synopsis">
<h2>Synopsis<a class="headerlink" href="#synopsis" title="Link to this heading">¶</a></h2>
<div class="highlight-fish-synopsis notranslate"><div class="highlight"><pre><span></span><span class="nf">trap</span><span class="w"> </span><span class="g g-Other">[</span><span class="no">OPTIONS</span><span class="g g-Other">]</span><span class="w"> </span><span class="g g-Other">[[</span><span class="no">ARG</span><span class="g g-Other">]</span><span class="w"> </span><span class="no">REASON</span><span class="w"> </span><span class="g g-Other">...</span><span class="no"> ]</span>
</pre></div>
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<section id="description">
<h2>Description<a class="headerlink" href="#description" title="Link to this heading">¶</a></h2>
<p><code class="docutils literal notranslate"><span class="pre">trap</span></code> is a wrapper around the fish event delivery framework. It exists for backwards compatibility with POSIX shells. For other uses, it is recommended to define an <a class="reference internal" href="../language.html#event"><span class="std std-ref">event handler</span></a>.</p>
<p>The following parameters are available:</p>
<dl class="simple">
<dt><em>ARG</em></dt><dd><p>Command to be executed on signal delivery.</p>
</dd>
<dt><em>REASON</em></dt><dd><p>Name of the event to trap. For example, a signal like <code class="docutils literal notranslate"><span class="pre">INT</span></code> or <code class="docutils literal notranslate"><span class="pre">SIGINT</span></code>, or the special symbol <code class="docutils literal notranslate"><span class="pre">EXIT</span></code>.</p>
</dd>
<dt><strong>-l</strong> or <strong>--list-signals</strong></dt><dd><p>Prints a list of signal names.</p>
</dd>
<dt><strong>-p</strong> or <strong>--print</strong></dt><dd><p>Prints all defined signal handlers.</p>
</dd>
<dt><strong>-h</strong> or <strong>--help</strong></dt><dd><p>Displays help about using this command.</p>
</dd>
</dl>
<p>If <em>ARG</em> and <em>REASON</em> are both specified, <em>ARG</em> is the command to be executed when the event specified by <em>REASON</em> occurs (e.g., the signal is delivered).</p>
<p>If <em>ARG</em> is absent (and there is a single <em>REASON</em>) or <code class="docutils literal notranslate"><span class="pre">-</span></code>, each specified signal is reset to its original disposition (the value it had upon entrance to the shell). If <em>ARG</em> is the null string the signal specified by each <em>REASON</em> is ignored by the shell and by the commands it invokes.</p>
<p>If <em>ARG</em> is not present and <strong>-p</strong> has been supplied, then the trap commands associated with each <em>REASON</em> are displayed. If no arguments are supplied or if only <strong>-p</strong> is given, <code class="docutils literal notranslate"><span class="pre">trap</span></code> prints the list of commands associated with each signal.</p>
<p>Signal names are case insensitive and the <code class="docutils literal notranslate"><span class="pre">SIG</span></code> prefix is optional. Trapping a signal will prevent fish from exiting in response to that signal.</p>
<p>The exit status is 1 if any <em>REASON</em> is invalid; otherwise trap returns 0.</p>
</section>
<section id="example">
<h2>Example<a class="headerlink" href="#example" title="Link to this heading">¶</a></h2>
<div class="highlight-fish-docs-samples notranslate"><div class="highlight"><pre><span></span><span class="nf">trap</span><span class="w"> </span><span class="s2">"status --print-stack-trace"</span><span class="w"> </span><span class="no">SIGUSR1</span>
<span class="c"># Prints a stack trace each time the SIGUSR1 signal is sent to the shell.</span>
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