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143 lines
3.8 KiB
Markdown
143 lines
3.8 KiB
Markdown
# Readline
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To use this module, do `require('readline')`. Readline allows reading of a
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stream (such as STDIN) on a line-by-line basis.
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Note that once you've invoked this module, your node program will not
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terminate until you've closed the interface, and the STDIN stream. Here's how
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to allow your program to gracefully terminate:
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var rl = require('readline');
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var i = rl.createInterface(process.stdin, process.stdout, null);
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i.question("What do you think of node.js?", function(answer) {
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// TODO: Log the answer in a database
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console.log("Thank you for your valuable feedback.");
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// These two lines together allow the program to terminate. Without
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// them, it would run forever.
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i.close();
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process.stdin.destroy();
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});
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## rl.createInterface(input, output, completer)
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Takes two streams and creates a readline interface. The `completer` function
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is used for autocompletion. When given a substring, it returns `[[substr1,
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substr2, ...], originalsubstring]`.
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Also `completer` can be run in async mode if it accepts two arguments:
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function completer(linePartial, callback) {
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callback(null, [['123'], linePartial]);
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}
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`createInterface` is commonly used with `process.stdin` and
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`process.stdout` in order to accept user input:
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var readline = require('readline'),
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rl = readline.createInterface(process.stdin, process.stdout);
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## Class: Interface
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The class that represents a readline interface with a stdin and stdout
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stream.
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### rl.setPrompt(prompt, length)
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Sets the prompt, for example when you run `node` on the command line, you see
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`> `, which is node's prompt.
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### rl.prompt()
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Readies readline for input from the user, putting the current `setPrompt`
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options on a new line, giving the user a new spot to write.
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### rl.question(query, callback)
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Prepends the prompt with `query` and invokes `callback` with the user's
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response. Displays the query to the user, and then invokes `callback` with the
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user's response after it has been typed.
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Example usage:
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interface.question('What is your favorite food?', function(answer) {
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console.log('Oh, so your favorite food is ' + answer);
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});
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### rl.close()
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Closes tty.
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### rl.pause()
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Pauses tty.
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### rl.resume()
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Resumes tty.
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### rl.write()
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Writes to tty.
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### Event: 'line'
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`function (line) {}`
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Emitted whenever the `in` stream receives a `\n`, usually received when the
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user hits enter, or return. This is a good hook to listen for user input.
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Example of listening for `line`:
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rl.on('line', function (cmd) {
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console.log('You just typed: '+cmd);
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});
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### Event: 'close'
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`function () {}`
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Emitted whenever the `in` stream receives a `^C` or `^D`, respectively known
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as `SIGINT` and `EOT`. This is a good way to know the user is finished using
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your program.
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Example of listening for `close`, and exiting the program afterward:
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rl.on('close', function() {
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console.log('goodbye!');
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process.exit(0);
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});
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Here's an example of how to use all these together to craft a tiny command
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line interface:
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var readline = require('readline'),
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rl = readline.createInterface(process.stdin, process.stdout),
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prefix = 'OHAI> ';
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rl.on('line', function(line) {
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switch(line.trim()) {
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case 'hello':
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console.log('world!');
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break;
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default:
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console.log('Say what? I might have heard `' + line.trim() + '`');
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break;
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}
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rl.setPrompt(prefix, prefix.length);
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rl.prompt();
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}).on('close', function() {
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console.log('Have a great day!');
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process.exit(0);
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});
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console.log(prefix + 'Good to see you. Try typing stuff.');
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rl.setPrompt(prefix, prefix.length);
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rl.prompt();
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Take a look at this slightly more complicated
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[example](https://gist.github.com/901104), and
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[http-console](https://github.com/cloudhead/http-console) for a real-life use
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case.
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