Craig Condon
300 lines
11 KiB
HTML
300 lines
11 KiB
HTML
<!doctype html>
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<title>REPL Node.js v0.8.14 Manual & Documentation</title>
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<li><a href="/" class="home">Home</a></li>
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<div id="column1" class="interior">
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<header>
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<h1>Node.js v0.8.14 Manual & Documentation</h1>
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<div id="gtoc">
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<p>
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<a href="index.html" name="toc">Index</a> |
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<a href="all.html">View on single page</a> |
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<a href="repl.json">View as JSON</a>
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</header>
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<div id="toc">
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<h2>Table of Contents</h2>
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<ul>
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<li><a href="#repl_repl">REPL</a><ul>
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<li><a href="#repl_repl_start_options">repl.start(options)</a><ul>
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<li><a href="#repl_event_exit">Event: 'exit'</a></li>
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</ul>
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</li>
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<li><a href="#repl_repl_features">REPL Features</a></li>
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</ul>
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</li>
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</ul>
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</div>
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<div id="apicontent">
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<h1>REPL<span><a class="mark" href="#repl_repl" id="repl_repl">#</a></span></h1>
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<p>A Read-Eval-Print-Loop (REPL) is available both as a standalone program and
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easily includable in other programs. The REPL provides a way to interactively
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run JavaScript and see the results. It can be used for debugging, testing, or
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just trying things out.
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</p>
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<p>By executing <code>node</code> without any arguments from the command-line you will be
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dropped into the REPL. It has simplistic emacs line-editing.
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</p>
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<pre><code>mjr:~$ node
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Type '.help' for options.
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> a = [ 1, 2, 3];
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[ 1, 2, 3 ]
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> a.forEach(function (v) {
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... console.log(v);
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... });
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1
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2
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3</code></pre>
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<p>For advanced line-editors, start node with the environmental variable
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<code>NODE_NO_READLINE=1</code>. This will start the main and debugger REPL in canonical
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terminal settings which will allow you to use with <code>rlwrap</code>.
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</p>
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<p>For example, you could add this to your bashrc file:
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</p>
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<pre><code>alias node="env NODE_NO_READLINE=1 rlwrap node"</code></pre>
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<h2>repl.start(options)<span><a class="mark" href="#repl_repl_start_options" id="repl_repl_start_options">#</a></span></h2>
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<p>Returns and starts a <code>REPLServer</code> instance. Accepts an "options" Object that
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takes the following values:
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</p>
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<ul>
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<li><p><code>prompt</code> - the prompt and <code>stream</code> for all I/O. Defaults to <code>> </code>.</p>
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</li>
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<li><p><code>input</code> - the readable stream to listen to. Defaults to <code>process.stdin</code>.</p>
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</li>
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<li><p><code>output</code> - the writable stream to write readline data to. Defaults to
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<code>process.stdout</code>.</p>
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</li>
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<li><p><code>terminal</code> - pass <code>true</code> if the <code>stream</code> should be treated like a TTY, and
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have ANSI/VT100 escape codes written to it. Defaults to checking <code>isTTY</code>
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on the <code>output</code> stream upon instantiation.</p>
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</li>
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<li><p><code>eval</code> - function that will be used to eval each given line. Defaults to
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an async wrapper for <code>eval()</code>. See below for an example of a custom <code>eval</code>.</p>
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</li>
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<li><p><code>useColors</code> - a boolean which specifies whether or not the <code>writer</code> function
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should output colors. If a different <code>writer</code> function is set then this does
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nothing. Defaults to the repl's <code>terminal</code> value.</p>
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</li>
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<li><p><code>useGlobal</code> - if set to <code>true</code>, then the repl will use the <code>global</code> object,
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instead of running scripts in a separate context. Defaults to <code>false</code>.</p>
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</li>
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<li><p><code>ignoreUndefined</code> - if set to <code>true</code>, then the repl will not output the
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return value of command if it's <code>undefined</code>. Defaults to <code>false</code>.</p>
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</li>
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<li><p><code>writer</code> - the function to invoke for each command that gets evaluated which
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returns the formatting (including coloring) to display. Defaults to
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<code>util.inspect</code>.</p>
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</li>
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</ul>
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<p>You can use your own <code>eval</code> function if it has following signature:
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</p>
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<pre><code>function eval(cmd, context, filename, callback) {
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callback(null, result);
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}</code></pre>
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<p>Multiple REPLs may be started against the same running instance of node. Each
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will share the same global object but will have unique I/O.
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</p>
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<p>Here is an example that starts a REPL on stdin, a Unix socket, and a TCP socket:
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</p>
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<pre><code>var net = require("net"),
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repl = require("repl");
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connections = 0;
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repl.start({
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prompt: "node via stdin> ",
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input: process.stdin,
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output: process.stdout
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});
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net.createServer(function (socket) {
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connections += 1;
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repl.start({
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prompt: "node via Unix socket> ",
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input: socket,
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output: socket
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}).on('exit', function() {
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socket.end();
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})
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}).listen("/tmp/node-repl-sock");
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net.createServer(function (socket) {
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connections += 1;
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repl.start({
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prompt: "node via TCP socket> ",
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input: socket,
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output: socket
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}).on('exit', function() {
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socket.end();
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});
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}).listen(5001);</code></pre>
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<p>Running this program from the command line will start a REPL on stdin. Other
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REPL clients may connect through the Unix socket or TCP socket. <code>telnet</code> is useful
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for connecting to TCP sockets, and <code>socat</code> can be used to connect to both Unix and
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TCP sockets.
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</p>
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<p>By starting a REPL from a Unix socket-based server instead of stdin, you can
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connect to a long-running node process without restarting it.
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</p>
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<p>For an example of running a "full-featured" (<code>terminal</code>) REPL over
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a <code>net.Server</code> and <code>net.Socket</code> instance, see: <a href="https://gist.github.com/2209310">https://gist.github.com/2209310</a>
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</p>
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<p>For an example of running a REPL instance over <code>curl(1)</code>,
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see: <a href="https://gist.github.com/2053342">https://gist.github.com/2053342</a>
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</p>
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<h3>Event: 'exit'<span><a class="mark" href="#repl_event_exit" id="repl_event_exit">#</a></span></h3>
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<p><code>function () {}</code>
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</p>
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<p>Emitted when the user exits the REPL in any of the defined ways. Namely, typing
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<code>.exit</code> at the repl, pressing Ctrl+C twice to signal SIGINT, or pressing Ctrl+D
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to signal "end" on the <code>input</code> stream.
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</p>
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<p>Example of listening for <code>exit</code>:
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</p>
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<pre><code>r.on('exit', function () {
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console.log('Got "exit" event from repl!');
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process.exit();
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});</code></pre>
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<h2>REPL Features<span><a class="mark" href="#repl_repl_features" id="repl_repl_features">#</a></span></h2>
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<!-- type=misc -->
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<p>Inside the REPL, Control+D will exit. Multi-line expressions can be input.
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Tab completion is supported for both global and local variables.
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</p>
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<p>The special variable <code>_</code> (underscore) contains the result of the last expression.
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</p>
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<pre><code>> [ "a", "b", "c" ]
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[ 'a', 'b', 'c' ]
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> _.length
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3
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> _ += 1
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4</code></pre>
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<p>The REPL provides access to any variables in the global scope. You can expose
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a variable to the REPL explicitly by assigning it to the <code>context</code> object
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associated with each <code>REPLServer</code>. For example:
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</p>
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<pre><code>// repl_test.js
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var repl = require("repl"),
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msg = "message";
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repl.start().context.m = msg;</code></pre>
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<p>Things in the <code>context</code> object appear as local within the REPL:
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</p>
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<pre><code>mjr:~$ node repl_test.js
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> m
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'message'</code></pre>
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<p>There are a few special REPL commands:
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</p>
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<ul>
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<li><code>.break</code> - While inputting a multi-line expression, sometimes you get lost
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or just don't care about completing it. <code>.break</code> will start over.</li>
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<li><code>.clear</code> - Resets the <code>context</code> object to an empty object and clears any
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multi-line expression.</li>
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<li><code>.exit</code> - Close the I/O stream, which will cause the REPL to exit.</li>
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<li><code>.help</code> - Show this list of special commands.</li>
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<li><code>.save</code> - Save the current REPL session to a file<blockquote>
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<p>.save ./file/to/save.js</p>
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</blockquote>
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</li>
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<li><code>.load</code> - Load a file into the current REPL session.<blockquote>
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<p>.load ./file/to/load.js</p>
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</blockquote>
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</li>
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</ul>
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<p>The following key combinations in the REPL have these special effects:
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</p>
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<ul>
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<li><code><ctrl>C</code> - Similar to the <code>.break</code> keyword. Terminates the current
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command. Press twice on a blank line to forcibly exit.</li>
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<li><code><ctrl>D</code> - Similar to the <code>.exit</code> keyword.</li>
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</ul>
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