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<!doctype html> <html lang="en"> <head> <meta charset="utf-8"> <title>Readline Node.js v0.10.35 Manual & Documentation</title> <link rel="stylesheet" href="assets/style.css"> <link rel="stylesheet" href="assets/sh.css"> <link rel="canonical" href="http://nodejs.org/api/readline.html"> <script type="text/javascript" src="//use.typekit.net/mse5tqx.js"></script> <script type="text/javascript">try{Typekit.load();}catch(e){}</script> </head> <body class="alt apidoc int docs" id="docs"> <div id="nav"> <img id="logo" src="assets/logo.svg" alt="node.js"> <ul> <li><a href="http://nodejs.org">Home</a></li> <li><a href="http://nodejs.org/download/">Downloads</a></li> <li class="active"><a href="http://nodejs.org/documentation/">Docs</a></li> <li><a href="http://nodejs.org/community/">Community</a></li> <li><a href="http://nodejs.org/about/">About</a></li> <li><a href="http://jobs.nodejs.org">Jobs</a></li> <li><a href="http://blog.nodejs.org">Blog</a></li> </ul> </div> <div id="content-wrap"> <div id="content" class="clearfix"> <div id="column2" class="interior">  <ul class="docs-nav"> <li><a href="http://nodejs.org/documentation/">About Docs</a></li> <li><a href="http://nodejs.org/documentation/tutorials/">Tutorials</a></li> <li><a href="http://nodejs.org/documentation/contributing/">Contributing</a></li> <li><a href="http://nodejs.org/documentation/localization/">Localization</a></li> <li class="active"><a href="http://nodejs.org/api/">API Docs</a></li> </ul> </div> <div id="column1" class="interior"> <header> <h1>Node.js v0.10.35 Manual & Documentation</h1> <div id="gtoc"> <p> <a href="index.html" name="toc">Index</a> | <a href="all.html">View on single page</a> | <a href="readline.json">View as JSON</a> </p> </div> <hr> </header> <div id="toc"> <h2>Table of Contents</h2> <ul> <li><a href="#readline_readline">Readline</a><ul> <li><a href="#readline_readline_createinterface_options">readline.createInterface(options)</a></li> <li><a href="#readline_class_interface">Class: Interface</a><ul> <li><a href="#readline_rl_setprompt_prompt_length">rl.setPrompt(prompt, length)</a></li> <li><a href="#readline_rl_prompt_preservecursor">rl.prompt([preserveCursor])</a></li> <li><a href="#readline_rl_question_query_callback">rl.question(query, callback)</a></li> <li><a href="#readline_rl_pause">rl.pause()</a></li> <li><a href="#readline_rl_resume">rl.resume()</a></li> <li><a href="#readline_rl_close">rl.close()</a></li> <li><a href="#readline_rl_write_data_key">rl.write(data, [key])</a></li> </ul> </li> <li><a href="#readline_events">Events</a><ul> <li><a href="#readline_event_line">Event: 'line'</a></li> <li><a href="#readline_event_pause">Event: 'pause'</a></li> <li><a href="#readline_event_resume">Event: 'resume'</a></li> <li><a href="#readline_event_close">Event: 'close'</a></li> <li><a href="#readline_event_sigint">Event: 'SIGINT'</a></li> <li><a href="#readline_event_sigtstp">Event: 'SIGTSTP'</a></li> <li><a href="#readline_event_sigcont">Event: 'SIGCONT'</a></li> </ul> </li> <li><a href="#readline_example_tiny_cli">Example: Tiny CLI</a></li> <li><a href="#readline_readline_cursorto_stream_x_y">readline.cursorTo(stream, x, y)</a></li> <li><a href="#readline_readline_movecursor_stream_dx_dy">readline.moveCursor(stream, dx, dy)</a></li> <li><a href="#readline_readline_clearline_stream_dir">readline.clearLine(stream, dir)</a></li> <li><a href="#readline_readline_clearscreendown_stream">readline.clearScreenDown(stream)</a></li> </ul> </li> </ul> </div> <div id="apicontent"> <h1>Readline<span><a class="mark" href="#readline_readline" id="readline_readline">#</a></span></h1> <pre class="api_stability_2">Stability: 2 - Unstable</pre><p>To use this module, do <code>require('readline')</code>. Readline allows reading of a stream (such as <code>process.stdin</code>) on a line-by-line basis. </p> <p>Note that once you've invoked this module, your node program will not terminate until you've closed the interface. Here's how to allow your program to gracefully exit: </p> <pre><code>var readline = require('readline'); var rl = readline.createInterface({ input: process.stdin, output: process.stdout }); rl.question("What do you think of node.js? ", function(answer) { // TODO: Log the answer in a database console.log("Thank you for your valuable feedback:", answer); rl.close(); });</code></pre> <h2>readline.createInterface(options)<span><a class="mark" href="#readline_readline_createinterface_options" id="readline_readline_createinterface_options">#</a></span></h2> <p>Creates a readline <code>Interface</code> instance. Accepts an "options" Object that takes the following values: </p> <ul> <li><p><code>input</code> - the readable stream to listen to (Required).</p> </li> <li><p><code>output</code> - the writable stream to write readline data to (Required).</p> </li> <li><p><code>completer</code> - an optional function that is used for Tab autocompletion. See below for an example of using this.</p> </li> <li><p><code>terminal</code> - pass <code>true</code> if the <code>input</code> and <code>output</code> streams should be treated like a TTY, and have ANSI/VT100 escape codes written to it. Defaults to checking <code>isTTY</code> on the <code>output</code> stream upon instantiation.</p> </li> </ul> <p>The <code>completer</code> function is given the current line entered by the user, and is supposed to return an Array with 2 entries: </p> <ol> <li><p>An Array with matching entries for the completion.</p> </li> <li><p>The substring that was used for the matching.</p> </li> </ol> <p>Which ends up looking something like: <code>[[substr1, substr2, ...], originalsubstring]</code>. </p> <p>Example: </p> <pre><code>function completer(line) { var completions = '.help .error .exit .quit .q'.split(' ') var hits = completions.filter(function(c) { return c.indexOf(line) == 0 }) // show all completions if none found return [hits.length ? hits : completions, line] }</code></pre> <p>Also <code>completer</code> can be run in async mode if it accepts two arguments: </p> <pre><code>function completer(linePartial, callback) { callback(null, [['123'], linePartial]); }</code></pre> <p><code>createInterface</code> is commonly used with <code>process.stdin</code> and <code>process.stdout</code> in order to accept user input: </p> <pre><code>var readline = require('readline'); var rl = readline.createInterface({ input: process.stdin, output: process.stdout });</code></pre> <p>Once you have a readline instance, you most commonly listen for the <code>"line"</code> event. </p> <p>If <code>terminal</code> is <code>true</code> for this instance then the <code>output</code> stream will get the best compatibility if it defines an <code>output.columns</code> property, and fires a <code>"resize"</code> event on the <code>output</code> if/when the columns ever change (<code>process.stdout</code> does this automatically when it is a TTY). </p> <h2>Class: Interface<span><a class="mark" href="#readline_class_interface" id="readline_class_interface">#</a></span></h2> <p>The class that represents a readline interface with an input and output stream. </p> <h3>rl.setPrompt(prompt, length)<span><a class="mark" href="#readline_rl_setprompt_prompt_length" id="readline_rl_setprompt_prompt_length">#</a></span></h3> <p>Sets the prompt, for example when you run <code>node</code> on the command line, you see <code>> </code>, which is node's prompt. </p> <h3>rl.prompt([preserveCursor])<span><a class="mark" href="#readline_rl_prompt_preservecursor" id="readline_rl_prompt_preservecursor">#</a></span></h3> <p>Readies readline for input from the user, putting the current <code>setPrompt</code> options on a new line, giving the user a new spot to write. Set <code>preserveCursor</code> to <code>true</code> to prevent the cursor placement being reset to <code>0</code>. </p> <p>This will also resume the <code>input</code> stream used with <code>createInterface</code> if it has been paused. </p> <h3>rl.question(query, callback)<span><a class="mark" href="#readline_rl_question_query_callback" id="readline_rl_question_query_callback">#</a></span></h3> <p>Prepends the prompt with <code>query</code> and invokes <code>callback</code> with the user's response. Displays the query to the user, and then invokes <code>callback</code> with the user's response after it has been typed. </p> <p>This will also resume the <code>input</code> stream used with <code>createInterface</code> if it has been paused. </p> <p>Example usage: </p> <pre><code>interface.question('What is your favorite food?', function(answer) { console.log('Oh, so your favorite food is ' + answer); });</code></pre> <h3>rl.pause()<span><a class="mark" href="#readline_rl_pause" id="readline_rl_pause">#</a></span></h3> <p>Pauses the readline <code>input</code> stream, allowing it to be resumed later if needed. </p> <h3>rl.resume()<span><a class="mark" href="#readline_rl_resume" id="readline_rl_resume">#</a></span></h3> <p>Resumes the readline <code>input</code> stream. </p> <h3>rl.close()<span><a class="mark" href="#readline_rl_close" id="readline_rl_close">#</a></span></h3> <p>Closes the <code>Interface</code> instance, relinquishing control on the <code>input</code> and <code>output</code> streams. The "close" event will also be emitted. </p> <h3>rl.write(data, [key])<span><a class="mark" href="#readline_rl_write_data_key" id="readline_rl_write_data_key">#</a></span></h3> <p>Writes <code>data</code> to <code>output</code> stream. <code>key</code> is an object literal to represent a key sequence; available if the terminal is a TTY. </p> <p>This will also resume the <code>input</code> stream if it has been paused. </p> <p>Example: </p> <pre><code>rl.write('Delete me!'); // Simulate ctrl+u to delete the line written previously rl.write(null, {ctrl: true, name: 'u'});</code></pre> <h2>Events<span><a class="mark" href="#readline_events" id="readline_events">#</a></span></h2> <h3>Event: 'line'<span><a class="mark" href="#readline_event_line" id="readline_event_line">#</a></span></h3> <p><code>function (line) {}</code> </p> <p>Emitted whenever the <code>input</code> stream receives a <code>\n</code>, usually received when the user hits enter, or return. This is a good hook to listen for user input. </p> <p>Example of listening for <code>line</code>: </p> <pre><code>rl.on('line', function (cmd) { console.log('You just typed: '+cmd); });</code></pre> <h3>Event: 'pause'<span><a class="mark" href="#readline_event_pause" id="readline_event_pause">#</a></span></h3> <p><code>function () {}</code> </p> <p>Emitted whenever the <code>input</code> stream is paused. </p> <p>Also emitted whenever the <code>input</code> stream is not paused and receives the <code>SIGCONT</code> event. (See events <code>SIGTSTP</code> and <code>SIGCONT</code>) </p> <p>Example of listening for <code>pause</code>: </p> <pre><code>rl.on('pause', function() { console.log('Readline paused.'); });</code></pre> <h3>Event: 'resume'<span><a class="mark" href="#readline_event_resume" id="readline_event_resume">#</a></span></h3> <p><code>function () {}</code> </p> <p>Emitted whenever the <code>input</code> stream is resumed. </p> <p>Example of listening for <code>resume</code>: </p> <pre><code>rl.on('resume', function() { console.log('Readline resumed.'); });</code></pre> <h3>Event: 'close'<span><a class="mark" href="#readline_event_close" id="readline_event_close">#</a></span></h3> <p><code>function () {}</code> </p> <p>Emitted when <code>close()</code> is called. </p> <p>Also emitted when the <code>input</code> stream receives its "end" event. The <code>Interface</code> instance should be considered "finished" once this is emitted. For example, when the <code>input</code> stream receives <code>^D</code>, respectively known as <code>EOT</code>. </p> <p>This event is also called if there is no <code>SIGINT</code> event listener present when the <code>input</code> stream receives a <code>^C</code>, respectively known as <code>SIGINT</code>. </p> <h3>Event: 'SIGINT'<span><a class="mark" href="#readline_event_sigint" id="readline_event_sigint">#</a></span></h3> <p><code>function () {}</code> </p> <p>Emitted whenever the <code>input</code> stream receives a <code>^C</code>, respectively known as <code>SIGINT</code>. If there is no <code>SIGINT</code> event listener present when the <code>input</code> stream receives a <code>SIGINT</code>, <code>pause</code> will be triggered. </p> <p>Example of listening for <code>SIGINT</code>: </p> <pre><code>rl.on('SIGINT', function() { rl.question('Are you sure you want to exit?', function(answer) { if (answer.match(/^y(es)?$/i)) rl.pause(); }); });</code></pre> <h3>Event: 'SIGTSTP'<span><a class="mark" href="#readline_event_sigtstp" id="readline_event_sigtstp">#</a></span></h3> <p><code>function () {}</code> </p> <p><strong>This does not work on Windows.</strong> </p> <p>Emitted whenever the <code>input</code> stream receives a <code>^Z</code>, respectively known as <code>SIGTSTP</code>. If there is no <code>SIGTSTP</code> event listener present when the <code>input</code> stream receives a <code>SIGTSTP</code>, the program will be sent to the background. </p> <p>When the program is resumed with <code>fg</code>, the <code>pause</code> and <code>SIGCONT</code> events will be emitted. You can use either to resume the stream. </p> <p>The <code>pause</code> and <code>SIGCONT</code> events will not be triggered if the stream was paused before the program was sent to the background. </p> <p>Example of listening for <code>SIGTSTP</code>: </p> <pre><code>rl.on('SIGTSTP', function() { // This will override SIGTSTP and prevent the program from going to the // background. console.log('Caught SIGTSTP.'); });</code></pre> <h3>Event: 'SIGCONT'<span><a class="mark" href="#readline_event_sigcont" id="readline_event_sigcont">#</a></span></h3> <p><code>function () {}</code> </p> <p><strong>This does not work on Windows.</strong> </p> <p>Emitted whenever the <code>input</code> stream is sent to the background with <code>^Z</code>, respectively known as <code>SIGTSTP</code>, and then continued with <code>fg(1)</code>. This event only emits if the stream was not paused before sending the program to the background. </p> <p>Example of listening for <code>SIGCONT</code>: </p> <pre><code>rl.on('SIGCONT', function() { // `prompt` will automatically resume the stream rl.prompt(); });</code></pre> <h2>Example: Tiny CLI<span><a class="mark" href="#readline_example_tiny_cli" id="readline_example_tiny_cli">#</a></span></h2> <p>Here's an example of how to use all these together to craft a tiny command line interface: </p> <pre><code>var readline = require('readline'), rl = readline.createInterface(process.stdin, process.stdout); rl.setPrompt('OHAI> '); rl.prompt(); rl.on('line', function(line) { switch(line.trim()) { case 'hello': console.log('world!'); break; default: console.log('Say what? I might have heard `' + line.trim() + '`'); break; } rl.prompt(); }).on('close', function() { console.log('Have a great day!'); process.exit(0); });</code></pre> <h2>readline.cursorTo(stream, x, y)<span><a class="mark" href="#readline_readline_cursorto_stream_x_y" id="readline_readline_cursorto_stream_x_y">#</a></span></h2> <p>Move cursor to the specified position in a given TTY stream. </p> <h2>readline.moveCursor(stream, dx, dy)<span><a class="mark" href="#readline_readline_movecursor_stream_dx_dy" id="readline_readline_movecursor_stream_dx_dy">#</a></span></h2> <p>Move cursor relative to it's current position in a given TTY stream. </p> <h2>readline.clearLine(stream, dir)<span><a class="mark" href="#readline_readline_clearline_stream_dir" id="readline_readline_clearline_stream_dir">#</a></span></h2> <p>Clears current line of given TTY stream in a specified direction. <code>dir</code> should have one of following values: </p> <ul> <li><code>-1</code> - to the left from cursor</li> <li><code>1</code> - to the right from cursor</li> <li><code>0</code> - the entire line</li> </ul> <h2>readline.clearScreenDown(stream)<span><a class="mark" href="#readline_readline_clearscreendown_stream" id="readline_readline_clearscreendown_stream">#</a></span></h2> <p>Clears the screen from the current position of the cursor down. </p> </div> </div> </div> </div> <div id="footer"> <div class="foot-1"> <a href="http://www.joyent.com"><h5>The Node.js Project is Sponsored by</h5> <img src="assets/joyent-footer.svg" width="200"> <p class="tag">Production Node +<br>High Performance Infrastructure</p></a> <a href="https://my.joyent.com/landing/signup/701800000015696" class="button getstarted">Get Started</a> </div> <div class="foot-2"> <div class="foot-nav"> <ul> <li><a href="http://nodejs.org/download/">Downloads</a></li> </ul> <ul> <li><a href="http://nodejs.org/documentation/">Documentation</a></li> <li><a href="http://nodejs.org/api/">API Docs</a></li> <li><a href="http://nodejs.org/documentation/tutorials/">Tutorials</a></li> <li><a href="http://nodejs.org/documentation/localization/">Localization</a></li> </ul> <ul> <li><a href="http://nodejs.org/community/">Community</a></li> <li><a href="https://github.com/joyent/node/issues">Github Issues</a></li> <li><a href="http://groups.google.com/group/nodejs">Mailing List</a></li> <li><a href="http://webchat.freenode.net/?channels=node.js">IRC</a></li> <li><a href="https://twitter.com/nodejs">Twitter</a></li> </ul> <ul> <li><a href="http://nodejs.org/about/">About</a></li> <li><a href="http://nodejs.org/about/organization/">Organization</a></li> <li><a href="http://nodejs.org/about/core-team/">Core Team</a></li> <li><a href="http://nodejs.org/about/resources/">Resources</a></li> </ul> <ul> <li><a href="http://blog.nodejs.org">Blog</a></li> </ul> </div> <p class="copyright">Copyright 2014 <a href="http://joyent.com/">Joyent, Inc</a>, Node.js is a <a href="https://nodejs.org/images/trademark-policy.pdf">trademark</a> of Joyent, Inc. <a href="https://raw.github.com/joyent/node/v0.10.35/LICENSE">View license</a>.</p> </div> </div> <script src="/sh_main.js"></script> <script src="/sh_javascript.min.js"></script> <script>highlight(undefined, undefined, 'pre');</script> <script> window._gaq = [['_setAccount', 'UA-10874194-2'], ['_trackPageview']]; (function(d, t) { var g = d.createElement(t), s = d.getElementsByTagName(t)[0]; g.src = '//www.google-analytics.com/ga.js'; s.parentNode.insertBefore(g, s); }(document, 'script')); </script> </body> </html>