readline-sync/README.md

# readlineSync

Synchronous [Readline](http://nodejs.org/api/readline.html) for interactively running.  
The interface is used with `process.stdin` and `process.stdout` in order to accept user input.

## Example

```js
var readlineSync = require('readline-sync');

var userName = readlineSync.question('May I have your name? :'); // Wait for user's response.
var favFood = readlineSync.question('Hi ' + userName + '! What is your favorite food? :');

console.log('Oh, ' + userName + ' likes ' + favFood + '!');
```

```
May I have your name? :AnSeki
Hi AnSeki! What is your favorite food? :chocolate
Oh, AnSeki likes chocolate!
```

## Installation

```
npm install readline-sync
```

## Methods

### question

```js
answer = readlineSync.question([query[, options]])
```

Displays the `query` to the user, and then returns the user's response after it has been typed.  
You can specify `options`. (see [Options](#options))

The `query` may be string, or may not be (e.g. number, Date, Object, etc.). This is converted to string (i.e. `toString` method is called) before it is displayed every time.

### prompt

```js
input = readlineSync.prompt([options])
```

Displays the current prompt (See `setPrompt` method) to the user, and then returns the user's response after it has been typed.  
You can specify `options`. (see [Options](#options))

### setPrompt

```js
currentPrompt = readlineSync.setPrompt([newPrompt])
```

Sets the prompt, for example when you run `node` on the command line, you see `> `, which is node's prompt. (See `prompt` method)

The `newPrompt` may be string, or may not be (e.g. number, Date, Object, etc.). This is converted to string (i.e. `toString` method is called) before it is displayed every time.  
For example, `[foo-directory]#` like a bash shell that show the current directory.

```js
// Simple Object that has toString method.
readlineSync.setPrompt({
  toString: function() {
    return '[' + require('path').basename(process.cwd()) + ']# '; // Get and show current directory.
  }
})
```

### setEncoding

```js
currentEncoding = readlineSync.setEncoding([newEncoding])
```

Set the encoding method of input (user's response) and output (`prompt` method and `question` method). Defaults to 'utf8'.

### setPrint

```js
readlineSync.setPrint([callback])
```

The specified `callback` Function is called when any outputs (`prompt` method and `question` method). Defaults to `undefined`.  
The `callback` is given two arguments the output text and `encoding`.

![sample](cl_01.png)

For example, this is used to pass plain texts to the Logger, when texts are colored.

```js
var readlineSync = require('readline-sync'),
  user, pw, command;
require('colors');

readlineSync.setPrint(function(display, encoding) {
  logger.log(display.stripColors); // Remove control characters.
});

console.log('Your account required.'.grey);
user = readlineSync.question('USER NAME'.white.inverse + ': ');
pw = readlineSync.question('PASSWORD'.white.inverse + ': ', {noEchoBack: true});
// Authorization ...
console.log(('Welcome, ' + user + '!').green.bold);

readlineSync.setPrompt('> '.bold.red);
command = readlineSync.prompt();
```

## Options

An `options` Object can be specified to `prompt` method and `question` method. This Object can have following properties.

### noEchoBack

Type: Boolean  
Default: `false`

If `true` is specified, echo back is avoided. It is used to hide the secret text (e.g. password) which is typed by user on screen.  
For example:

```js
password = readlineSync.question('PASSWORD :', {noEchoBack: true});
console.log('Login ...');
```

The typed text is not shown on screen.

```shell
PASSWORD :
Login ...
```

### noTrim

Type: Boolean  
Default: `false`

By default, the leading and trailing white spaces are removed from typed text. If `true` is specified, those are not removed.

## With Task Runner

The easy way to control the flow of task runner by the user's response:
* [Grunt](http://gruntjs.com/) plugin: [grunt-confirm](https://github.com/anseki/grunt-confirm)
* [gulp](http://gulpjs.com/) plugin: [gulp-confirm](https://github.com/anseki/gulp-confirm)

If you want to control the flow of task runner (e.g. [Grunt](http://gruntjs.com/)), call readlineSync in a task callback that is called by task runner. Then the flow of tasks is paused and it is controlled by user.

Example: by using [grunt-task-helper](https://github.com/anseki/grunt-task-helper)

```shell
$ grunt
Running "fileCopy" task
Files already exist:
  file-a.png
  file-b.js
Overwrite? (y/n) :y
file-a.png copied.
file-b.js copied.
Done.
```

`Gruntfile.js`

```js
grunt.initConfig({
  taskHelper: {
    fileCopy: {
      options: {
        handlerByTask: function() {
          // Abort the task if user don't want.
          return readlineSync.question('Overwrite? (y/n) :')
            .toLowerCase() === 'y';
          // Or process.exit()
        },
        filesArray: []
      },
      ...
    }
  },
  copy: {
    fileCopy: {
      files: '<%= taskHelper.fileCopy.options.filesArray %>'
    }
  }
});
```

## Note

### Platforms

The stdin interfaces are different by platforms. If the platform doesn't support interactively reading from stdin, an error is thrown.

```js
try {
  answer = readlineSync.question('What is your favorite food? :');
} catch (e) {
  console.error(e);
  process.exit(1);
}
```

### Reading by shell

readlineSync tries reading from stdin by shell if it is needed. And if the running Node doesn't support the [Synchronous Process Execution](http://nodejs.org/api/child_process.html#child_process_synchronous_process_creation) (i.e. Node v0.10-), it use "piping via files" for synchronous running.  
As everyone knows, "piping via files" is no good. It blocks event loop and a process. It may make your script be slow.

Why did I choose it? :

+ The good modules (native addon) for synchronous execution exist. But node-gyp can't compile those in some platforms or Node versions.
+ I think that the security is important more than the speed. Some modules have problem about security. (Those don't protect data.) I think that the speed is not needed usually, because readlineSync is used while user types keys.

## Release History
 * 2015-02-12           v0.5.5          Support the Synchronous Process Execution of Node v0.12(v0.11).
 * 2015-01-27           v0.5.0          Add `options.noTrim`.
 * 2014-07-12           v0.4.0          Add `options.noEchoBack`.
 * 2014-07-12           v0.3.0          Add `setPrint()`.
 * 2013-08-30           v0.2.0          Rewrite exporting methods.
 * 2013-08-29           v0.1.0          Initial release.