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            <h1>Node.js v0.10.9 Manual &amp; Documentation</h1>
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              <p>
                <a href="index.html" name="toc">Index</a> |
                <a href="all.html">View on single page</a> |
                <a href="debugger.json">View as JSON</a>
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          <div id="toc">
            <h2>Table of Contents</h2>
            <ul>
<li><a href="#debugger_debugger">Debugger</a><ul>
<li><a href="#debugger_watchers">Watchers</a></li>
<li><a href="#debugger_commands_reference">Commands reference</a><ul>
<li><a href="#debugger_stepping">Stepping</a></li>
<li><a href="#debugger_breakpoints">Breakpoints</a></li>
<li><a href="#debugger_info">Info</a></li>
<li><a href="#debugger_execution_control">Execution control</a></li>
<li><a href="#debugger_various">Various</a></li>
</ul>
</li>
<li><a href="#debugger_advanced_usage">Advanced Usage</a></li>
</ul>
</li>
</ul>

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          <div id="apicontent">
            <h1>Debugger<span><a class="mark" href="#debugger_debugger" id="debugger_debugger">#</a></span></h1>
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<pre class="api_stability_3">Stability: 3 - Stable</pre><!-- type=misc -->
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<p>V8 comes with an extensive debugger which is accessible out-of-process via a
simple <a href="http://code.google.com/p/v8/wiki/DebuggerProtocol">TCP protocol</a>.
Node has a built-in client for this debugger. To use this, start Node with the
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<code>debug</code> argument; a prompt will appear:
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</p>
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<pre><code>% node debug myscript.js
&lt; debugger listening on port 5858
connecting... ok
break in /home/indutny/Code/git/indutny/myscript.js:1
  1 x = 5;
  2 setTimeout(function () {
  3   debugger;
debug&gt;</code></pre>
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<p>Node&#39;s debugger client doesn&#39;t support the full range of commands, but
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simple step and inspection is possible. By putting the statement <code>debugger;</code>
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into the source code of your script, you will enable a breakpoint.
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</p>
<p>For example, suppose <code>myscript.js</code> looked like this:
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</p>
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<pre><code>// myscript.js
x = 5;
setTimeout(function () {
  debugger;
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  console.log(&quot;world&quot;);
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}, 1000);
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console.log(&quot;hello&quot;);</code></pre>
<p>Then once the debugger is run, it will break on line 4.
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</p>
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<pre><code>% node debug myscript.js
&lt; debugger listening on port 5858
connecting... ok
break in /home/indutny/Code/git/indutny/myscript.js:1
  1 x = 5;
  2 setTimeout(function () {
  3   debugger;
debug&gt; cont
&lt; hello
break in /home/indutny/Code/git/indutny/myscript.js:3
  1 x = 5;
  2 setTimeout(function () {
  3   debugger;
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  4   console.log(&quot;world&quot;);
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  5 }, 1000);
debug&gt; next
break in /home/indutny/Code/git/indutny/myscript.js:4
  2 setTimeout(function () {
  3   debugger;
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  4   console.log(&quot;world&quot;);
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  5 }, 1000);
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  6 console.log(&quot;hello&quot;);
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debug&gt; repl
Press Ctrl + C to leave debug repl
&gt; x
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&gt; 2+2
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debug&gt; next
&lt; world
break in /home/indutny/Code/git/indutny/myscript.js:5
  3   debugger;
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  4   console.log(&quot;world&quot;);
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  5 }, 1000);
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  6 console.log(&quot;hello&quot;);
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  7
debug&gt; quit
%</code></pre>
<p>The <code>repl</code> command allows you to evaluate code remotely. The <code>next</code> command
steps over to the next line. There are a few other commands available and more
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to come. Type <code>help</code> to see others.
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</p>
<h2>Watchers<span><a class="mark" href="#debugger_watchers" id="debugger_watchers">#</a></span></h2>
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<p>You can watch expression and variable values while debugging your code.
On every breakpoint each expression from the watchers list will be evaluated
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in the current context and displayed just before the breakpoint&#39;s source code
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listing.
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</p>
<p>To start watching an expression, type <code>watch(&quot;my_expression&quot;)</code>. <code>watchers</code>
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prints the active watchers. To remove a watcher, type
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<code>unwatch(&quot;my_expression&quot;)</code>.

</p>
<h2>Commands reference<span><a class="mark" href="#debugger_commands_reference" id="debugger_commands_reference">#</a></span></h2>
<h3>Stepping<span><a class="mark" href="#debugger_stepping" id="debugger_stepping">#</a></span></h3>
<ul>
<li><code>cont</code>, <code>c</code> - Continue execution</li>
<li><code>next</code>, <code>n</code> - Step next</li>
<li><code>step</code>, <code>s</code> - Step in</li>
<li><code>out</code>, <code>o</code> - Step out</li>
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<li><code>pause</code> - Pause running code (like pause button in Developer Tools)</li>
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</ul>
<h3>Breakpoints<span><a class="mark" href="#debugger_breakpoints" id="debugger_breakpoints">#</a></span></h3>
<div class="signature"><ul>
<li><code>setBreakpoint()</code>, <code>sb()</code> - Set breakpoint on current line</li>
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<li><code>setBreakpoint(line)</code>, <code>sb(line)</code> - Set breakpoint on specific line</li>
<li><code>setBreakpoint(&#39;fn()&#39;)</code>, <code>sb(...)</code> - Set breakpoint on a first statement in
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functions body</li>
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<li><code>setBreakpoint(&#39;script.js&#39;, 1)</code>, <code>sb(...)</code> - Set breakpoint on first line of
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script.js</li>
<li><code>clearBreakpoint</code>, <code>cb(...)</code> - Clear breakpoint</li>
</div></ul>
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<p>It is also possible to set a breakpoint in a file (module) that
isn&#39;t loaded yet:

</p>
<pre><code>% ./node debug test/fixtures/break-in-module/main.js
&lt; debugger listening on port 5858
connecting to port 5858... ok
break in test/fixtures/break-in-module/main.js:1
  1 var mod = require(&#39;./mod.js&#39;);
  2 mod.hello();
  3 mod.hello();
debug&gt; setBreakpoint(&#39;mod.js&#39;, 23)
Warning: script &#39;mod.js&#39; was not loaded yet.
  1 var mod = require(&#39;./mod.js&#39;);
  2 mod.hello();
  3 mod.hello();
debug&gt; c
break in test/fixtures/break-in-module/mod.js:23
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debug&gt;</code></pre>
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<h3>Info<span><a class="mark" href="#debugger_info" id="debugger_info">#</a></span></h3>
<div class="signature"><ul>
<li><code>backtrace</code>, <code>bt</code> - Print backtrace of current execution frame</li>
<li><code>list(5)</code> - List scripts source code with 5 line context (5 lines before and
after)</li>
<li><code>watch(expr)</code> - Add expression to watch list</li>
<li><code>unwatch(expr)</code> - Remove expression from watch list</li>
<li><code>watchers</code> - List all watchers and their values (automatically listed on each
breakpoint)</li>
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<li><code>repl</code> - Open debugger&#39;s repl for evaluation in debugging script&#39;s context</li>
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</div></ul>
<h3>Execution control<span><a class="mark" href="#debugger_execution_control" id="debugger_execution_control">#</a></span></h3>
<div class="signature"><ul>
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<li><code>run</code> - Run script (automatically runs on debugger&#39;s start)</li>
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<li><code>restart</code> - Restart script</li>
<li><code>kill</code> - Kill script</li>
</div></ul>
<h3>Various<span><a class="mark" href="#debugger_various" id="debugger_various">#</a></span></h3>
<div class="signature"><ul>
<li><code>scripts</code> - List all loaded scripts</li>
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<li><code>version</code> - Display v8&#39;s version</li>
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</div></ul>
<h2>Advanced Usage<span><a class="mark" href="#debugger_advanced_usage" id="debugger_advanced_usage">#</a></span></h2>
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<p>The V8 debugger can be enabled and accessed either by starting Node with
the <code>--debug</code> command-line flag or by signaling an existing Node process
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with <code>SIGUSR1</code>.
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</p>
<p>Once a process has been set in debug mode with this it can be connected to
with the node debugger. Either connect to the <code>pid</code> or the URI to the debugger.
The syntax is:

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</p>
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<ul>
<li><code>node debug -p &lt;pid&gt;</code> - Connects to the process via the <code>pid</code></li>
<li>`node debug <URI> - Connects to the process via the URI such as localhost:5858</li>
</ul>
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