all - Node.js Manual & Documentation (original) (raw)

Table Of Contents

Synopsis

An example of a web server written with Node which responds with 'Hello World':

var http = require('http');

http.createServer(function (request, response) {
  response.writeHead(200, {'Content-Type': 'text/plain'});
  response.end('Hello World\n');
}).listen(8124);

console.log('Server running at http://127.0.0.1:8124/');

To run the server, put the code into a file called example.js and execute it with the node program

> node example.js
Server running at http://127.0.0.1:8124/

All of the examples in the documentation can be run similarly.

Global Objects

These object are available in all modules. Some of these objects aren't actually in the global scope but in the module scope - this will be noted.

global

The global namespace object.

In browsers, the top-level scope is the global scope. That means that in browsers if you're in the global scope var something will define a global variable. In Node this is different. The top-level scope is not the global scope; var something inside a Node module will be local to that module.

process

The process object. See the process object section.

console

Used to print to stdout and stderr. See the stdio section.

require()

To require modules. See the Modules section.require isn't actually a global but rather local to each module.

require.resolve()

Use the internal require() machinery to look up the location of a module, but rather than loading the module, just return the resolved filename.

require.cache

Modules are cached in this object when they are required. By deleting a key value from this object, the next require will reload the module.

require.paths

An array of search paths for require(). This array can be modified to add custom paths.

Example: add a new path to the beginning of the search list

require.paths.unshift('/usr/local/node');

__filename

The filename of the script being executed. This is the absolute path, and not necessarily the same filename passed in as a command line argument.

Example: running node example.js from /Users/mjr

console.log(__filename);
// /Users/mjr/example.js

__filename isn't actually a global but rather local to each module.

__dirname

The dirname of the script being executed.

Example: running node example.js from /Users/mjr

console.log(__dirname);
// /Users/mjr

__dirname isn't actually a global but rather local to each module.

module

A reference to the current module. In particularmodule.exports is the same as the exports object. See src/node.jsfor more information.module isn't actually a global but rather local to each module.

exports

An object which is shared between all instances of the current module and made accessible through require().exports is the same as the module.exports object. See src/node.jsfor more information.exports isn't actually a global but rather local to each module.

setTimeout(cb, ms)

clearTimeout(t)

setInterval(cb, ms)

clearInterval(t)

The timer functions are global variables. See the timers section.

console

Browser-like object for printing to stdout and stderr.

console.log()

Prints to stdout with newline. This function can take multiple arguments in aprintf()-like way. Example:

console.log('count: %d', count);

If formating elements are not found in the first string then util.inspectis used on each argument.

console.info()

Same as console.log.

console.warn()

console.error()

Same as console.log but prints to stderr.

console.dir(obj)

Uses util.inspect on obj and prints resulting string to stderr.

console.time(label)

Mark a time.

console.timeEnd(label)

Finish timer, record output. Example

console.time('100-elements');
for (var i = 0; i < 100; i++) {
  ;
}
console.timeEnd('100-elements');

console.trace()

Print a stack trace to stderr of the current position.

console.assert()

Same as assert.ok().

Timers

setTimeout(callback, delay, [arg], [...])

To schedule execution of callback after delay milliseconds. Returns atimeoutId for possible use with clearTimeout(). Optionally, you can also pass arguments to the callback.

clearTimeout(timeoutId)

Prevents a timeout from triggering.

setInterval(callback, delay, [arg], [...])

To schedule the repeated execution of callback every delay milliseconds. Returns a intervalId for possible use with clearInterval(). Optionally, you can also pass arguments to the callback.

clearInterval(intervalId)

Stops a interval from triggering.

Modules

Node has a simple module loading system. In Node, files and modules are in one-to-one correspondence. As an example, foo.js loads the modulecircle.js in the same directory.

The contents of foo.js:

var circle = require('./circle.js');
console.log( 'The area of a circle of radius 4 is '
           + circle.area(4));

The contents of circle.js:

var PI = Math.PI;

exports.area = function (r) {
  return PI * r * r;
};

exports.circumference = function (r) {
  return 2 * PI * r;
};

The module circle.js has exported the functions area() andcircumference(). To export an object, add to the special exportsobject.

Variables local to the module will be private. In this example the variable PI is private to circle.js.

Core Modules

Node has several modules compiled into the binary. These modules are described in greater detail elsewhere in this documentation.

The core modules are defined in node's source in the lib/ folder.

Core modules are always preferentially loaded if their identifier is passed to require(). For instance, require('http') will always return the built in HTTP module, even if there is a file by that name.

File Modules

If the exact filename is not found, then node will attempt to load the required filename with the added extension of .js, and then .node.

.js files are interpreted as JavaScript text files, and .node files are interpreted as compiled addon modules loaded with dlopen.

A module prefixed with '/' is an absolute path to the file. For example, require('/home/marco/foo.js') will load the file at/home/marco/foo.js.

A module prefixed with './' is relative to the file calling require(). That is, circle.js must be in the same directory as foo.js forrequire('./circle') to find it.

Without a leading '/' or './' to indicate a file, the module is either a "core module" or is loaded from a node_modules folder.

Loading from `node_modules` Folders

If the module identifier passed to require() is not a native module, and does not begin with '/', '../', or './', then node starts at the parent directory of the current module, and adds /node_modules, and attempts to load the module from that location.

If it is not found there, then it moves to the parent directory, and so on, until the root of the tree is reached.

For example, if the file at '/home/ry/projects/foo.js' calledrequire('bar.js'), then node would look in the following locations, in this order:

This allows programs to localize their dependencies, so that they do not clash.

Folders as Modules

It is convenient to organize programs and libraries into self-contained directories, and then provide a single entry point to that library. There are three ways in which a folder may be passed to require() as an argument.

The first is to create a package.json file in the root of the folder, which specifies a main module. An example package.json file might look like this:

{ "name" : "some-library",
  "main" : "./lib/some-library.js" }

If this was in a folder at ./some-library, thenrequire('./some-library') would attempt to load./some-library/lib/some-library.js.

This is the extent of Node's awareness of package.json files.

If there is no package.json file present in the directory, then node will attempt to load an index.js or index.node file out of that directory. For example, if there was no package.json file in the above example, then require('./some-library') would attempt to load:

Caching

Modules are cached after the first time they are loaded. This means (among other things) that every call to require('foo') will get exactly the same object returned, if it would resolve to the same file.

Multiple calls to require('foo') may not cause the module code to be executed multiple times. This is an important feature. With it, "partially done" objects can be returned, thus allowing transitive dependencies to be loaded even when they would cause cycles.

If you want to have a module execute code multiple times, then export a function, and call that function.

Module Caching Caveats

Modules are cached based on their resolved filename. Since modules may resolve to a different filename based on the location of the calling module (loading from node_modules folders), it is not a _guarantee_that require('foo') will always return the exact same object, if it would resolve to different files.

module.exports

The exports object is created by the Module system. Sometimes this is not acceptable, many want their module to be an instance of some class. To do this assign the desired export object to module.exports. For example suppose we were making a module called a.js

var EventEmitter = require('events').EventEmitter;

module.exports = new EventEmitter();

// Do some work, and after some time emit
// the 'ready' event from the module itself.
setTimeout(function() {
  module.exports.emit('ready');
}, 1000);

Then in another file we could do

var a = require('./a');
a.on('ready', function() {
  console.log('module a is ready');
});

Note that assignment to module.exports must be done immediately. It cannot be done in any callbacks. This does not work:

x.js:

setTimeout(function() {
  module.exports = { a: "hello" };
}, 0);

y.js:

var x = require('./x');
console.log(x.a);

All Together...

To get the exact filename that will be loaded when require() is called, use the require.resolve() function.

Putting together all of the above, here is the high-level algorithm in pseudocode of what require.resolve does:

require(X) from module at path Y
1. If X is a core module,
   a. return the core module
   b. STOP
2. If X begins with './' or '/' or '../'
   a. LOAD_AS_FILE(Y + X)
   b. LOAD_AS_DIRECTORY(Y + X)
3. LOAD_NODE_MODULES(X, dirname(Y))
4. THROW "not found"

LOAD_AS_FILE(X)
1. If X is a file, load X as JavaScript text.  STOP
2. If X.js is a file, load X.js as JavaScript text.  STOP
3. If X.node is a file, load X.node as binary addon.  STOP

LOAD_AS_DIRECTORY(X)
1. If X/package.json is a file,
   a. Parse X/package.json, and look for "main" field.
   b. let M = X + (json main field)
   c. LOAD_AS_FILE(M)
2. LOAD_AS_FILE(X/index)

LOAD_NODE_MODULES(X, START)
1. let DIRS=NODE_MODULES_PATHS(START)
2. for each DIR in DIRS:
   a. LOAD_AS_FILE(DIR/X)
   b. LOAD_AS_DIRECTORY(DIR/X)

NODE_MODULES_PATHS(START)
1. let PARTS = path split(START)
2. let ROOT = index of first instance of "node_modules" in PARTS, or 0
3. let I = count of PARTS - 1
4. let DIRS = []
5. while I > ROOT,
   a. if PARTS[I] = "node_modules" CONTINUE
   c. DIR = path join(PARTS[0 .. I] + "node_modules")
   b. DIRS = DIRS + DIR
   c. let I = I - 1
6. return DIRS

Loading from the `require.paths` Folders

In node, require.paths is an array of strings that represent paths to be searched for modules when they are not prefixed with '/', './', or'../'. For example, if require.paths were set to:

[ '/home/micheil/.node_modules',
  '/usr/local/lib/node_modules' ]

Then calling require('bar/baz.js') would search the following locations:

The require.paths array can be mutated at run time to alter this behavior.

It is set initially from the NODE_PATH environment variable, which is a colon-delimited list of absolute paths. In the previous example, the NODE_PATH environment variable might have been set to:

/home/micheil/.node_modules:/usr/local/lib/node_modules

Loading from the require.paths locations is only performed if the module could not be found using the node_modules algorithm above. Global modules are lower priority than bundled dependencies.

**Note:** Please Avoid Modifying `require.paths`

require.paths may disappear in a future release.

While it seemed like a good idea at the time, and enabled a lot of useful experimentation, in practice a mutable require.paths list is often a troublesome source of confusion and headaches.

Setting `require.paths` to some other value does nothing.

This does not do what one might expect:

require.paths = [ '/usr/lib/node' ];

All that does is lose the reference to the actual node module lookup paths, and create a new reference to some other thing that isn't used for anything.

Putting relative paths in `require.paths` is... weird.

If you do this:

require.paths.push('./lib');

then it does not add the full resolved path to where ./libis on the filesystem. Instead, it literally adds './lib', meaning that if you do require('y.js') in /a/b/x.js, then it'll look in /a/b/lib/y.js. If you then did require('y.js') in/l/m/n/o/p.js, then it'd look in /l/m/n/o/lib/y.js.

In practice, people have used this as an ad hoc way to bundle dependencies, but this technique is brittle.

Zero Isolation

There is (by regrettable design), only one require.paths array used by all modules.

As a result, if one node program comes to rely on this behavior, it may permanently and subtly alter the behavior of all other node programs in the same process. As the application stack grows, we tend to assemble functionality, and those parts interact in ways that are difficult to predict.

Accessing the main module

When a file is run directly from Node, require.main is set to itsmodule. That means that you can determine whether a file has been run directly by testing

require.main === module

For a file foo.js, this will be true if run via node foo.js, butfalse if run by require('./foo').

Because module provides a filename property (normally equivalent to__filename), the entry point of the current application can be obtained by checking require.main.filename.

Addenda: Package Manager Tips

The semantics of Node's require() function were designed to be general enough to support a number of sane directory structures. Package manager programs such as dpkg, rpm, and npm will hopefully find it possible to build native packages from Node modules without modification.

Below we give a suggested directory structure that could work:

Let's say that we wanted to have the folder at/usr/lib/node/<some-package>/<some-version> hold the contents of a specific version of a package.

Packages can depend on one another. In order to install package foo, you may have to install a specific version of package bar. The bar package may itself have dependencies, and in some cases, these dependencies may even collide or form cycles.

Since Node looks up the realpath of any modules it loads (that is, resolves symlinks), and then looks for their dependencies in thenode_modules folders as described above, this situation is very simple to resolve with the following architecture:

Thus, even if a cycle is encountered, or if there are dependency conflicts, every module will be able to get a version of its dependency that it can use.

When the code in the foo package does require('bar'), it will get the version that is symlinked into /usr/lib/node/foo/1.2.3/node_modules/bar. Then, when the code in the bar package calls require('quux'), it'll get the version that is symlinked into/usr/lib/node/bar/4.3.2/node_modules/quux.

Furthermore, to make the module lookup process even more optimal, rather than putting packages directly in /usr/lib/node, we could put them in/usr/lib/node_modules/<name>/<version>. Then node will not bother looking for missing dependencies in /usr/node_modules or /node_modules.

In order to make modules available to the node REPL, it might be useful to also add the /usr/lib/node_modules folder to the $NODE_PATH environment variable. Since the module lookups using node_modules folders are all relative, and based on the real path of the files making the calls torequire(), the packages themselves can be anywhere.

Addons

Addons are dynamically linked shared objects. They can provide glue to C and C++ libraries. The API (at the moment) is rather complex, involving knowledge of several libraries:

Node statically compiles all its dependencies into the executable. When compiling your module, you don't need to worry about linking to any of these libraries.

To get started let's make a small Addon which does the following except in C++:

exports.hello = 'world';

To get started we create a file hello.cc:

#include <v8.h>

using namespace v8;

extern "C" void
init (Handle<Object> target)
{
  HandleScope scope;
  target->Set(String::New("hello"), String::New("world"));
}

This source code needs to be built into hello.node, the binary Addon. To do this we create a file called wscript which is python code and looks like this:

srcdir = '.'
blddir = 'build'
VERSION = '0.0.1'

def set_options(opt):
  opt.tool_options('compiler_cxx')

def configure(conf):
  conf.check_tool('compiler_cxx')
  conf.check_tool('node_addon')

def build(bld):
  obj = bld.new_task_gen('cxx', 'shlib', 'node_addon')
  obj.target = 'hello'
  obj.source = 'hello.cc'

Running node-waf configure build will create a filebuild/default/hello.node which is our Addon.

node-waf is just WAF, the python-based build system. node-waf is provided for the ease of users.

All Node addons must export a function called init with this signature:

extern 'C' void init (Handle<Object> target)

For the moment, that is all the documentation on addons. Please seehttps://github.com/ry/node_postgres for a real example.

process

The process object is a global object and can be accessed from anywhere. It is an instance of EventEmitter.

Event: 'exit'

function () {}

Emitted when the process is about to exit. This is a good hook to perform constant time checks of the module's state (like for unit tests). The main event loop will no longer be run after the 'exit' callback finishes, so timers may not be scheduled.

Example of listening for exit:

process.on('exit', function () {
  process.nextTick(function () {
   console.log('This will not run');
  });
  console.log('About to exit.');
});

Event: 'uncaughtException'

function (err) { }

Emitted when an exception bubbles all the way back to the event loop. If a listener is added for this exception, the default action (which is to print a stack trace and exit) will not occur.

Example of listening for uncaughtException:

process.on('uncaughtException', function (err) {
  console.log('Caught exception: ' + err);
});

setTimeout(function () {
  console.log('This will still run.');
}, 500);

// Intentionally cause an exception, but don't catch it.
nonexistentFunc();
console.log('This will not run.');

Note that uncaughtException is a very crude mechanism for exception handling. Using try / catch in your program will give you more control over your program's flow. Especially for server programs that are designed to stay running forever, uncaughtException can be a useful safety mechanism.

Signal Events

function () {}

Emitted when the processes receives a signal. See sigaction(2) for a list of standard POSIX signal names such as SIGINT, SIGUSR1, etc.

Example of listening for SIGINT:

// Start reading from stdin so we don't exit.
process.stdin.resume();

process.on('SIGINT', function () {
  console.log('Got SIGINT.  Press Control-D to exit.');
});

An easy way to send the SIGINT signal is with Control-C in most terminal programs.

process.stdout

A Writable Stream to stdout.

Example: the definition of console.log

console.log = function (d) {
  process.stdout.write(d + '\n');
};

process.stderr

A writable stream to stderr. Writes on this stream are blocking.

process.stdin

A Readable Stream for stdin. The stdin stream is paused by default, so one must call process.stdin.resume() to read from it.

Example of opening standard input and listening for both events:

process.stdin.resume();
process.stdin.setEncoding('utf8');

process.stdin.on('data', function (chunk) {
  process.stdout.write('data: ' + chunk);
});

process.stdin.on('end', function () {
  process.stdout.write('end');
});

process.argv

An array containing the command line arguments. The first element will be 'node', the second element will be the name of the JavaScript file. The next elements will be any additional command line arguments.

// print process.argv
process.argv.forEach(function (val, index, array) {
  console.log(index + ': ' + val);
});

This will generate:

$ node process-2.js one two=three four
0: node
1: /Users/mjr/work/node/process-2.js
2: one
3: two=three
4: four

process.execPath

This is the absolute pathname of the executable that started the process.

Example:

/usr/local/bin/node

process.chdir(directory)

Changes the current working directory of the process or throws an exception if that fails.

console.log('Starting directory: ' + process.cwd());
try {
  process.chdir('/tmp');
  console.log('New directory: ' + process.cwd());
}
catch (err) {
  console.log('chdir: ' + err);
}

process.cwd()

Returns the current working directory of the process.

console.log('Current directory: ' + process.cwd());

process.env

An object containing the user environment. See environ(7).

process.exit(code=0)

Ends the process with the specified code. If omitted, exit uses the 'success' code 0.

To exit with a 'failure' code:

process.exit(1);

The shell that executed node should see the exit code as 1.

process.getgid()

Gets the group identity of the process. (See getgid(2).) This is the numerical group id, not the group name.

console.log('Current gid: ' + process.getgid());

process.setgid(id)

Sets the group identity of the process. (See setgid(2).) This accepts either a numerical ID or a groupname string. If a groupname is specified, this method blocks while resolving it to a numerical ID.

console.log('Current gid: ' + process.getgid());
try {
  process.setgid(501);
  console.log('New gid: ' + process.getgid());
}
catch (err) {
  console.log('Failed to set gid: ' + err);
}

process.getuid()

Gets the user identity of the process. (See getuid(2).) This is the numerical userid, not the username.

console.log('Current uid: ' + process.getuid());

process.setuid(id)

Sets the user identity of the process. (See setuid(2).) This accepts either a numerical ID or a username string. If a username is specified, this method blocks while resolving it to a numerical ID.

console.log('Current uid: ' + process.getuid());
try {
  process.setuid(501);
  console.log('New uid: ' + process.getuid());
}
catch (err) {
  console.log('Failed to set uid: ' + err);
}

process.version

A compiled-in property that exposes NODE_VERSION.

console.log('Version: ' + process.version);

process.installPrefix

A compiled-in property that exposes NODE_PREFIX.

console.log('Prefix: ' + process.installPrefix);

process.kill(pid, signal='SIGTERM')

Send a signal to a process. pid is the process id and signal is the string describing the signal to send. Signal names are strings like 'SIGINT' or 'SIGUSR1'. If omitted, the signal will be 'SIGTERM'. See kill(2) for more information.

Note that just because the name of this function is process.kill, it is really just a signal sender, like the kill system call. The signal sent may do something other than kill the target process.

Example of sending a signal to yourself:

process.on('SIGHUP', function () {
  console.log('Got SIGHUP signal.');
});

setTimeout(function () {
  console.log('Exiting.');
  process.exit(0);
}, 100);

process.kill(process.pid, 'SIGHUP');

process.pid

The PID of the process.

console.log('This process is pid ' + process.pid);

process.title

Getter/setter to set what is displayed in 'ps'.

process.platform

What platform you're running on. 'linux2', 'darwin', etc.

console.log('This platform is ' + process.platform);

process.memoryUsage()

Returns an object describing the memory usage of the Node process.

var util = require('util');

console.log(util.inspect(process.memoryUsage()));

This will generate:

{ rss: 4935680,
  vsize: 41893888,
  heapTotal: 1826816,
  heapUsed: 650472 }

heapTotal and heapUsed refer to V8's memory usage.

process.nextTick(callback)

On the next loop around the event loop call this callback. This is not a simple alias to setTimeout(fn, 0), it's much more efficient.

process.nextTick(function () {
  console.log('nextTick callback');
});

process.umask([mask])

Sets or reads the process's file mode creation mask. Child processes inherit the mask from the parent process. Returns the old mask if mask argument is given, otherwise returns the current mask.

var oldmask, newmask = 0644;

oldmask = process.umask(newmask);
console.log('Changed umask from: ' + oldmask.toString(8) +
            ' to ' + newmask.toString(8));

util

These functions are in the module 'util'. Use require('util') to access them.

util.debug(string)

A synchronous output function. Will block the process and output string immediately to stderr.

require('util').debug('message on stderr');

util.log(string)

Output with timestamp on stdout.

require('util').log('Timestamped message.');

util.inspect(object, showHidden=false, depth=2)

Return a string representation of object, which is useful for debugging.

If showHidden is true, then the object's non-enumerable properties will be shown too.

If depth is provided, it tells inspect how many times to recurse while formatting the object. This is useful for inspecting large complicated objects.

The default is to only recurse twice. To make it recurse indefinitely, pass in null for depth.

Example of inspecting all properties of the util object:

var util = require('util');

console.log(util.inspect(util, true, null));

util.pump(readableStream, writableStream, [callback])

Experimental

Read the data from readableStream and send it to the writableStream. When writableStream.write(data) returns false readableStream will be paused until the drain event occurs on the writableStream. callback gets an error as its only argument and is called when writableStream is closed or when an error occurs.

util.inherits(constructor, superConstructor)

Inherit the prototype methods from oneconstructorinto another. The prototype of constructor will be set to a new object created from superConstructor.

As an additional convenience, superConstructor will be accessible through the constructor.super_ property.

var util = require("util");
var events = require("events");

function MyStream() {
    events.EventEmitter.call(this);
}

util.inherits(MyStream, events.EventEmitter);

MyStream.prototype.write = function(data) {
    this.emit("data", data);
}

var stream = new MyStream();

console.log(stream instanceof events.EventEmitter); // true
console.log(MyStream.super_ === events.EventEmitter); // true

stream.on("data", function(data) {
    console.log('Received data: "' + data + '"');
})
stream.write("It works!"); // Received data: "It works!"

Events

Many objects in Node emit events: a net.Server emits an event each time a peer connects to it, a fs.readStream emits an event when the file is opened. All objects which emit events are instances of events.EventEmitter. You can access this module by doing: require("events");

Typically, event names are represented by a camel-cased string, however, there aren't any strict restrictions on that, as any string will be accepted.

Functions can then be attached to objects, to be executed when an event is emitted. These functions are called listeners.

events.EventEmitter

To access the EventEmitter class, require('events').EventEmitter.

When an EventEmitter instance experiences an error, the typical action is to emit an 'error' event. Error events are treated as a special case in node. If there is no listener for it, then the default action is to print a stack trace and exit the program.

All EventEmitters emit the event 'newListener' when new listeners are added.

emitter.addListener(event, listener)

emitter.on(event, listener)

Adds a listener to the end of the listeners array for the specified event.

server.on('connection', function (stream) {
  console.log('someone connected!');
});

emitter.once(event, listener)

Adds a one time listener for the event. The listener is invoked only the first time the event is fired, after which it is removed.

server.once('connection', function (stream) {
  console.log('Ah, we have our first user!');
});

emitter.removeListener(event, listener)

Remove a listener from the listener array for the specified event.Caution: changes array indices in the listener array behind the listener.

var callback = function(stream) {
  console.log('someone connected!');
};
server.on('connection', callback);
// ...
server.removeListener('connection', callback);

emitter.removeAllListeners(event)

Removes all listeners from the listener array for the specified event.

emitter.setMaxListeners(n)

By default EventEmitters will print a warning if more than 10 listeners are added to it. This is a useful default which helps finding memory leaks. Obviously not all Emitters should be limited to 10. This function allows that to be increased. Set to zero for unlimited.

emitter.listeners(event)

Returns an array of listeners for the specified event. This array can be manipulated, e.g. to remove listeners.

server.on('connection', function (stream) {
  console.log('someone connected!');
});
console.log(util.inspect(server.listeners('connection')); // [ [Function] ]

emitter.emit(event, [arg1], [arg2], [...])

Execute each of the listeners in order with the supplied arguments.

Event: 'newListener'

function (event, listener) { }

This event is emitted any time someone adds a new listener.

Buffers

Pure Javascript is Unicode friendly but not nice to binary data. When dealing with TCP streams or the file system, it's necessary to handle octet streams. Node has several strategies for manipulating, creating, and consuming octet streams.

Raw data is stored in instances of the Buffer class. A Buffer is similar to an array of integers but corresponds to a raw memory allocation outside the V8 heap. A Buffer cannot be resized.

The Buffer object is global.

Converting between Buffers and JavaScript string objects requires an explicit encoding method. Here are the different string encodings;

new Buffer(size)

Allocates a new buffer of size octets.

new Buffer(array)

Allocates a new buffer using an array of octets.

new Buffer(str, encoding='utf8')

Allocates a new buffer containing the given str.

buffer.write(string, offset=0, encoding='utf8')

Writes string to the buffer at offset using the given encoding. Returns number of octets written. If buffer did not contain enough space to fit the entire string, it will write a partial amount of the string. The method will not write partial characters.

Example: write a utf8 string into a buffer, then print it

buf = new Buffer(256);
len = buf.write('\u00bd + \u00bc = \u00be', 0);
console.log(len + " bytes: " + buf.toString('utf8', 0, len));

The number of characters written (which may be different than the number of bytes written) is set in Buffer._charsWritten and will be overwritten the next time buf.write() is called.

buffer.toString(encoding, start=0, end=buffer.length)

Decodes and returns a string from buffer data encoded with encodingbeginning at start and ending at end.

See buffer.write() example, above.

buffer[index]

Get and set the octet at index. The values refer to individual bytes, so the legal range is between 0x00 and 0xFF hex or 0 and 255.

Example: copy an ASCII string into a buffer, one byte at a time:

str = "node.js";
buf = new Buffer(str.length);

for (var i = 0; i < str.length ; i++) {
  buf[i] = str.charCodeAt(i);
}

console.log(buf);

// node.js

Buffer.isBuffer(obj)

Tests if obj is a Buffer.

Buffer.byteLength(string, encoding='utf8')

Gives the actual byte length of a string. This is not the same asString.prototype.length since that returns the number of characters in a string.

Example:

str = '\u00bd + \u00bc = \u00be';

console.log(str + ": " + str.length + " characters, " +
  Buffer.byteLength(str, 'utf8') + " bytes");

// ½ + ¼ = ¾: 9 characters, 12 bytes

buffer.length

The size of the buffer in bytes. Note that this is not necessarily the size of the contents. length refers to the amount of memory allocated for the buffer object. It does not change when the contents of the buffer are changed.

buf = new Buffer(1234);

console.log(buf.length);
buf.write("some string", "ascii", 0);
console.log(buf.length);

// 1234
// 1234

buffer.copy(targetBuffer, targetStart=0, sourceStart=0, sourceEnd=buffer.length)

Does a memcpy() between buffers.

Example: build two Buffers, then copy buf1 from byte 16 through byte 19 into buf2, starting at the 8th byte in buf2.

buf1 = new Buffer(26);
buf2 = new Buffer(26);

for (var i = 0 ; i < 26 ; i++) {
  buf1[i] = i + 97; // 97 is ASCII a
  buf2[i] = 33; // ASCII !
}

buf1.copy(buf2, 8, 16, 20);
console.log(buf2.toString('ascii', 0, 25));

// !!!!!!!!qrst!!!!!!!!!!!!!

buffer.slice(start, end=buffer.length)

Returns a new buffer which references the same memory as the old, but offset and cropped by the start and endindexes.

Modifying the new buffer slice will modify memory in the original buffer!

Example: build a Buffer with the ASCII alphabet, take a slice, then modify one byte from the original Buffer.

var buf1 = new Buffer(26);

for (var i = 0 ; i < 26 ; i++) {
  buf1[i] = i + 97; // 97 is ASCII a
}

var buf2 = buf1.slice(0, 3);
console.log(buf2.toString('ascii', 0, buf2.length));
buf1[0] = 33;
console.log(buf2.toString('ascii', 0, buf2.length));

// abc
// !bc

Streams

A stream is an abstract interface implemented by various objects in Node. For example a request to an HTTP server is a stream, as is stdout. Streams are readable, writable, or both. All streams are instances of EventEmitter.

Readable Stream

A Readable Stream has the following methods, members, and events.

Event: 'data'

function (data) { }

The 'data' event emits either a Buffer (by default) or a string ifsetEncoding() was used.

Event: 'end'

function () { }

Emitted when the stream has received an EOF (FIN in TCP terminology). Indicates that no more 'data' events will happen. If the stream is also writable, it may be possible to continue writing.

Event: 'error'

function (exception) { }

Emitted if there was an error receiving data.

Event: 'close'

function () { }

Emitted when the underlying file descriptor has been closed. Not all streams will emit this. (For example, an incoming HTTP request will not emit'close'.)

Event: 'fd'

function (fd) { }

Emitted when a file descriptor is received on the stream. Only UNIX streams support this functionality; all others will simply never emit this event.

stream.readable

A boolean that is true by default, but turns false after an 'error'occurred, the stream came to an 'end', or destroy() was called.

stream.setEncoding(encoding)

Makes the data event emit a string instead of a Buffer. encoding can be'utf8', 'ascii', or 'base64'.

stream.pause()

Pauses the incoming 'data' events.

stream.resume()

Resumes the incoming 'data' events after a pause().

stream.destroy()

Closes the underlying file descriptor. Stream will not emit any more events.

stream.destroySoon()

After the write queue is drained, close the file descriptor.

stream.pipe(destination, [options])

This is a Stream.prototype method available on all Streams.

Connects this read stream to destination WriteStream. Incoming data on this stream gets written to destination. The destination and source streams are kept in sync by pausing and resuming as necessary.

Emulating the Unix cat command:

process.stdin.resume();
process.stdin.pipe(process.stdout);

By default end() is called on the destination when the source stream emitsend, so that destination is no longer writable. Pass { end: false } asoptions to keep the destination stream open.

This keeps process.stdout open so that "Goodbye" can be written at the end.

process.stdin.resume();

process.stdin.pipe(process.stdout, { end: false });

process.stdin.on("end", function() {
  process.stdout.write("Goodbye\n");
});

NOTE: If the source stream does not support pause() and resume(), this function adds simple definitions which simply emit 'pause' and 'resume' events on the source stream.

Writable Stream

A Writable Stream has the following methods, members, and events.

Event: 'drain'

function () { }

Emitted after a write() method was called that returned false to indicate that it is safe to write again.

Event: 'error'

function (exception) { }

Emitted on error with the exception exception.

Event: 'close'

function () { }

Emitted when the underlying file descriptor has been closed.

Event: 'pipe'

function (src) { }

Emitted when the stream is passed to a readable stream's pipe method.

stream.writable

A boolean that is true by default, but turns false after an 'error'occurred or end() / destroy() was called.

stream.write(string, encoding='utf8', [fd])

Writes string with the given encoding to the stream. Returns true if the string has been flushed to the kernel buffer. Returns false to indicate that the kernel buffer is full, and the data will be sent out in the future. The 'drain' event will indicate when the kernel buffer is empty again. The encoding defaults to 'utf8'.

If the optional fd parameter is specified, it is interpreted as an integral file descriptor to be sent over the stream. This is only supported for UNIX streams, and is silently ignored otherwise. When writing a file descriptor in this manner, closing the descriptor before the stream drains risks sending an invalid (closed) FD.

stream.write(buffer)

Same as the above except with a raw buffer.

stream.end()

Terminates the stream with EOF or FIN.

stream.end(string, encoding)

Sends string with the given encoding and terminates the stream with EOF or FIN. This is useful to reduce the number of packets sent.

stream.end(buffer)

Same as above but with a buffer.

stream.destroy()

Closes the underlying file descriptor. Stream will not emit any more events.

stream.destroySoon()

After the write queue is drained, close the file descriptor. destroySoon()can still destroy straight away, as long as there is no data left in the queue for writes.

Crypto

Use require('crypto') to access this module.

The crypto module requires OpenSSL to be available on the underlying platform. It offers a way of encapsulating secure credentials to be used as part of a secure HTTPS net or http connection.

It also offers a set of wrappers for OpenSSL's hash, hmac, cipher, decipher, sign and verify methods.

crypto.createCredentials(details)

Creates a credentials object, with the optional details being a dictionary with keys:

If no 'ca' details are given, then node.js will use the default publicly trusted list of CAs as given inhttp://mxr.mozilla.org/mozilla/source/security/nss/lib/ckfw/builtins/certdata.txt.

crypto.createHash(algorithm)

Creates and returns a hash object, a cryptographic hash with the given algorithm which can be used to generate hash digests.

algorithm is dependent on the available algorithms supported by the version of OpenSSL on the platform. Examples are 'sha1', 'md5', 'sha256', 'sha512', etc. On recent releases, openssl list-message-digest-algorithms will display the available digest algorithms.

Example: this program that takes the sha1 sum of a file

var filename = process.argv[2];
var crypto = require('crypto');
var fs = require('fs');

var shasum = crypto.createHash('sha1');

var s = fs.ReadStream(filename);
s.on('data', function(d) {
  shasum.update(d);
});

s.on('end', function() {
  var d = shasum.digest('hex');
  console.log(d + '  ' + filename);
});

hash.update(data)

Updates the hash content with the given data. This can be called many times with new data as it is streamed.

hash.digest(encoding='binary')

Calculates the digest of all of the passed data to be hashed. The encoding can be 'hex', 'binary' or 'base64'.

crypto.createHmac(algorithm, key)

Creates and returns a hmac object, a cryptographic hmac with the given algorithm and key.

algorithm is dependent on the available algorithms supported by OpenSSL - see createHash above.key is the hmac key to be used.

hmac.update(data)

Update the hmac content with the given data. This can be called many times with new data as it is streamed.

hmac.digest(encoding='binary')

Calculates the digest of all of the passed data to the hmac. The encoding can be 'hex', 'binary' or 'base64'.

crypto.createCipher(algorithm, key)

Creates and returns a cipher object, with the given algorithm and key.

algorithm is dependent on OpenSSL, examples are 'aes192', etc. On recent releases, openssl list-cipher-algorithms will display the available cipher algorithms.

cipher.update(data, input_encoding='binary', output_encoding='binary')

Updates the cipher with data, the encoding of which is given in input_encodingand can be 'utf8', 'ascii' or 'binary'. The output_encoding specifies the output format of the enciphered data, and can be 'binary', 'base64' or 'hex'.

Returns the enciphered contents, and can be called many times with new data as it is streamed.

cipher.final(output_encoding='binary')

Returns any remaining enciphered contents, with output_encoding being one of: 'binary', 'base64' or 'hex'.

crypto.createDecipher(algorithm, key)

Creates and returns a decipher object, with the given algorithm and key. This is the mirror of the cipher object above.

decipher.update(data, input_encoding='binary', output_encoding='binary')

Updates the decipher with data, which is encoded in 'binary', 'base64' or 'hex'. The output_decoding specifies in what format to return the deciphered plaintext: 'binary', 'ascii' or 'utf8'.

decipher.final(output_encoding='binary')

Returns any remaining plaintext which is deciphered, with output_encoding being one of: 'binary', 'ascii' or 'utf8'.

crypto.createSign(algorithm)

Creates and returns a signing object, with the given algorithm. On recent OpenSSL releases, openssl list-public-key-algorithms will display the available signing algorithms. Examples are 'RSA-SHA256'.

signer.update(data)

Updates the signer object with data. This can be called many times with new data as it is streamed.

signer.sign(private_key, output_format='binary')

Calculates the signature on all the updated data passed through the signer.private_key is a string containing the PEM encoded private key for signing.

Returns the signature in output_format which can be 'binary', 'hex' or 'base64'.

crypto.createVerify(algorithm)

Creates and returns a verification object, with the given algorithm. This is the mirror of the signing object above.

verifier.update(data)

Updates the verifier object with data. This can be called many times with new data as it is streamed.

verifier.verify(object, signature, signature_format='binary')

Verifies the signed data by using the object and signature. object is a string containing a PEM encoded object, which can be one of RSA public key, DSA public key, or X.509 certificate. signature is the previously calculated signature for the data, in the signature_format which can be 'binary','hex' or 'base64'.

Returns true or false depending on the validity of the signature for the data and public key.

TLS (SSL)

Use require('tls') to access this module.

The tls module uses OpenSSL to provide Transport Layer Security and/or Secure Socket Layer: encrypted stream communication.

TLS/SSL is a public/private key infrastructure. Each client and each server must have a private key. A private key is created like this

openssl genrsa -out ryans-key.pem 1024

All severs and some clients need to have a certificate. Certificates are public keys signed by a Certificate Authority or self-signed. The first step to getting a certificate is to create a "Certificate Signing Request" (CSR) file. This is done with:

openssl req -new -key ryans-key.pem -out ryans-csr.pem

To create a self-signed certificate with the CSR, do this:

openssl x509 -req -in ryans-csr.pem -signkey ryans-key.pem -out ryans-cert.pem

Alternatively you can send the CSR to a Certificate Authority for signing.

(TODO: docs on creating a CA, for now interested users should just look attest/fixtures/keys/Makefile in the Node source code)

s = tls.connect(port, [host], [options], callback)

Creates a new client connection to the given port and host. (If hostdefaults to localhost.) options should be an object which specifies

tls.connect() returns a cleartext CryptoStream object.

After the TLS/SSL handshake the callback is called. The callback will be called no matter if the server's certificate was authorized or not. It is up to the user to test s.authorized to see if the server certificate was signed by one of the specified CAs. If s.authorized === false then the error can be found in s.authorizationError.

STARTTLS

In the v0.4 branch no function exists for starting a TLS session on an already existing TCP connection. This is possible it just requires a bit of work. The technique is to use tls.createSecurePair() which returns two streams: an encrypted stream and a plaintext stream. The encrypted stream is then piped to the socket, the plaintext stream is what the user interacts with thereafter.

Here is some code that does it.

tls.Server

This class is a subclass of net.Server and has the same methods on it. Instead of accepting just raw TCP connections, this accepts encrypted connections using TLS or SSL.

Here is a simple example echo server:

var tls = require('tls');
var fs = require('fs');

var options = {
  key: fs.readFileSync('server-key.pem'),
  cert: fs.readFileSync('server-cert.pem')
};

tls.createServer(options, function (s) {
  s.write("welcome!\n");
  s.pipe(s);
}).listen(8000);

You can test this server by connecting to it with openssl s_client:

openssl s_client -connect 127.0.0.1:8000

tls.createServer(options, secureConnectionListener)

This is a constructor for the tls.Server class. The options object has these possibilities:

Event: 'secureConnection'

function (cleartextStream) {}

This event is emitted after a new connection has been successfully handshaked. The argument is a duplex instance of stream.Stream. It has all the common stream methods and events.

cleartextStream.authorized is a boolean value which indicates if the client has verified by one of the supplied certificate authorities for the server. If cleartextStream.authorized is false, thencleartextStream.authorizationError is set to describe how authorization failed. Implied but worth mentioning: depending on the settings of the TLS server, you unauthorized connections may be accepted.

server.listen(port, [host], [callback])

Begin accepting connections on the specified port and host. If thehost is omitted, the server will accept connections directed to any IPv4 address (INADDR_ANY).

This function is asynchronous. The last parameter callback will be called when the server has been bound.

See net.Server for more information.

server.close()

Stops the server from accepting new connections. This function is asynchronous, the server is finally closed when the server emits a 'close'event.

server.maxConnections

Set this property to reject connections when the server's connection count gets high.

server.connections

The number of concurrent connections on the server.

File System

File I/O is provided by simple wrappers around standard POSIX functions. To use this module do require('fs'). All the methods have asynchronous and synchronous forms.

The asynchronous form always take a completion callback as its last argument. The arguments passed to the completion callback depend on the method, but the first argument is always reserved for an exception. If the operation was completed successfully, then the first argument will be null or undefined.

Here is an example of the asynchronous version:

var fs = require('fs');

fs.unlink('/tmp/hello', function (err) {
  if (err) throw err;
  console.log('successfully deleted /tmp/hello');
});

Here is the synchronous version:

var fs = require('fs');

fs.unlinkSync('/tmp/hello')
console.log('successfully deleted /tmp/hello');

With the asynchronous methods there is no guaranteed ordering. So the following is prone to error:

fs.rename('/tmp/hello', '/tmp/world', function (err) {
  if (err) throw err;
  console.log('renamed complete');
});
fs.stat('/tmp/world', function (err, stats) {
  if (err) throw err;
  console.log('stats: ' + JSON.stringify(stats));
});

It could be that fs.stat is executed before fs.rename. The correct way to do this is to chain the callbacks.

fs.rename('/tmp/hello', '/tmp/world', function (err) {
  if (err) throw err;
  fs.stat('/tmp/world', function (err, stats) {
    if (err) throw err;
    console.log('stats: ' + JSON.stringify(stats));
  });
});

In busy processes, the programmer is strongly encouraged to use the asynchronous versions of these calls. The synchronous versions will block the entire process until they complete--halting all connections.

Relative path to filename can be used, remember however that this path will be relative to process.cwd().

fs.rename(path1, path2, [callback])

Asynchronous rename(2). No arguments other than a possible exception are given to the completion callback.

fs.renameSync(path1, path2)

Synchronous rename(2).

fs.truncate(fd, len, [callback])

Asynchronous ftruncate(2). No arguments other than a possible exception are given to the completion callback.

fs.truncateSync(fd, len)

Synchronous ftruncate(2).

fs.chown(path, mode, [callback])

Asycnronous chown(2). No arguments other than a possible exception are given to the completion callback.

fs.chownSync(path, mode)

Synchronous chown(2).

fs.fchown(path, mode, [callback])

Asycnronous fchown(2). No arguments other than a possible exception are given to the completion callback.

fs.fchownSync(path, mode)

Synchronous fchown(2).

fs.lchown(path, mode, [callback])

Asycnronous lchown(2). No arguments other than a possible exception are given to the completion callback.

fs.lchownSync(path, mode)

Synchronous lchown(2).

fs.chmod(path, mode, [callback])

Asynchronous chmod(2). No arguments other than a possible exception are given to the completion callback.

fs.chmodSync(path, mode)

Synchronous chmod(2).

fs.fchmod(fd, mode, [callback])

Asynchronous fchmod(2). No arguments other than a possible exception are given to the completion callback.

fs.fchmodSync(path, mode)

Synchronous fchmod(2).

fs.lchmod(fd, mode, [callback])

Asynchronous lchmod(2). No arguments other than a possible exception are given to the completion callback.

fs.lchmodSync(path, mode)

Synchronous lchmod(2).

fs.stat(path, [callback])

Asynchronous stat(2). The callback gets two arguments (err, stats) wherestats is a `fs.Stats` object. It looks like this:

{ dev: 2049,
  ino: 305352,
  mode: 16877,
  nlink: 12,
  uid: 1000,
  gid: 1000,
  rdev: 0,
  size: 4096,
  blksize: 4096,
  blocks: 8,
  atime: '2009-06-29T11:11:55Z',
  mtime: '2009-06-29T11:11:40Z',
  ctime: '2009-06-29T11:11:40Z' }

See the fs.Stats section below for more information.

fs.lstat(path, [callback])

Asynchronous lstat(2). The callback gets two arguments (err, stats) wherestats is a fs.Stats object. lstat() is identical to stat(), except that ifpath is a symbolic link, then the link itself is stat-ed, not the file that it refers to.

fs.fstat(fd, [callback])

Asynchronous fstat(2). The callback gets two arguments (err, stats) wherestats is a fs.Stats object. fstat() is identical to stat(), except that the file to be stat-ed is specified by the file descriptor fd.

fs.statSync(path)

Synchronous stat(2). Returns an instance of fs.Stats.

fs.lstatSync(path)

Synchronous lstat(2). Returns an instance of fs.Stats.

fs.fstatSync(fd)

Synchronous fstat(2). Returns an instance of fs.Stats.

fs.link(srcpath, dstpath, [callback])

Asynchronous link(2). No arguments other than a possible exception are given to the completion callback.

fs.linkSync(srcpath, dstpath)

Synchronous link(2).

fs.symlink(linkdata, path, [callback])

Asynchronous symlink(2). No arguments other than a possible exception are given to the completion callback.

fs.symlinkSync(linkdata, path)

Synchronous symlink(2).

fs.readlink(path, [callback])

Asynchronous readlink(2). The callback gets two arguments (err, resolvedPath).

fs.readlinkSync(path)

Synchronous readlink(2). Returns the resolved path.

fs.realpath(path, [callback])

Asynchronous realpath(2). The callback gets two arguments (err, resolvedPath).

fs.realpathSync(path)

Synchronous realpath(2). Returns the resolved path.

fs.unlink(path, [callback])

Asynchronous unlink(2). No arguments other than a possible exception are given to the completion callback.

fs.unlinkSync(path)

Synchronous unlink(2).

fs.rmdir(path, [callback])

Asynchronous rmdir(2). No arguments other than a possible exception are given to the completion callback.

fs.rmdirSync(path)

Synchronous rmdir(2).

fs.mkdir(path, mode, [callback])

Asynchronous mkdir(2). No arguments other than a possible exception are given to the completion callback.

fs.mkdirSync(path, mode)

Synchronous mkdir(2).

fs.readdir(path, [callback])

Asynchronous readdir(3). Reads the contents of a directory. The callback gets two arguments (err, files) where files is an array of the names of the files in the directory excluding '.' and '..'.

fs.readdirSync(path)

Synchronous readdir(3). Returns an array of filenames excluding '.' and'..'.

fs.close(fd, [callback])

Asynchronous close(2). No arguments other than a possible exception are given to the completion callback.

fs.closeSync(fd)

Synchronous close(2).

fs.open(path, flags, [mode], [callback])

Asynchronous file open. See open(2). flags can be:

mode defaults to 0666. The callback gets two arguments (err, fd).

fs.openSync(path, flags, [mode])

Synchronous open(2).

fs.write(fd, buffer, offset, length, position, [callback])

Write buffer to the file specified by fd.

offset and length determine the part of the buffer to be written.

position refers to the offset from the beginning of the file where this data should be written. If position is null, the data will be written at the current position. See pwrite(2).

The callback will be given three arguments (err, written, buffer) where writtenspecifies how many bytes were written into buffer.

Note that it is unsafe to use fs.write multiple times on the same file without waiting for the callback. For this scenario,fs.createWriteStream is strongly recommended.

fs.writeSync(fd, buffer, offset, length, position)

Synchronous version of buffer-based fs.write(). Returns the number of bytes written.

fs.writeSync(fd, str, position, encoding='utf8')

Synchronous version of string-based fs.write(). Returns the number of bytes written.

fs.read(fd, buffer, offset, length, position, [callback])

Read data from the file specified by fd.

buffer is the buffer that the data will be written to.

offset is offset within the buffer where writing will start.

length is an integer specifying the number of bytes to read.

position is an integer specifying where to begin reading from in the file. If position is null, data will be read from the current file position.

The callback is given the three arguments, (err, bytesRead, buffer).

fs.readSync(fd, buffer, offset, length, position)

Synchronous version of buffer-based fs.read. Returns the number ofbytesRead.

fs.readSync(fd, length, position, encoding)

Synchronous version of string-based fs.read. Returns the number ofbytesRead.

fs.readFile(filename, [encoding], [callback])

Asynchronously reads the entire contents of a file. Example:

fs.readFile('/etc/passwd', function (err, data) {
  if (err) throw err;
  console.log(data);
});

The callback is passed two arguments (err, data), where data is the contents of the file.

If no encoding is specified, then the raw buffer is returned.

fs.readFileSync(filename, [encoding])

Synchronous version of fs.readFile. Returns the contents of the filename.

If encoding is specified then this function returns a string. Otherwise it returns a buffer.

fs.writeFile(filename, data, encoding='utf8', [callback])

Asynchronously writes data to a file, replacing the file if it already exists.data can be a string or a buffer.

Example:

fs.writeFile('message.txt', 'Hello Node', function (err) {
  if (err) throw err;
  console.log('It\'s saved!');
});

fs.writeFileSync(filename, data, encoding='utf8')

The synchronous version of fs.writeFile.

fs.watchFile(filename, [options], listener)

Watch for changes on filename. The callback listener will be called each time the file is accessed.

The second argument is optional. The options if provided should be an object containing two members a boolean, persistent, and interval, a polling value in milliseconds. The default is { persistent: true, interval: 0 }.

The listener gets two arguments the current stat object and the previous stat object:

fs.watchFile(f, function (curr, prev) {
  console.log('the current mtime is: ' + curr.mtime);
  console.log('the previous mtime was: ' + prev.mtime);
});

These stat objects are instances of fs.Stat.

If you want to be notified when the file was modified, not just accessed you need to compare curr.mtime and `prev.mtime.

fs.unwatchFile(filename)

Stop watching for changes on filename.

fs.Stats

Objects returned from fs.stat() and fs.lstat() are of this type.

fs.ReadStream

ReadStream is a Readable Stream.

Event: 'open'

function (fd) { }

fd is the file descriptor used by the ReadStream.

fs.createReadStream(path, [options])

Returns a new ReadStream object (See Readable Stream).

options is an object with the following defaults:

{ flags: 'r',
  encoding: null,
  fd: null,
  mode: 0666,
  bufferSize: 64 * 1024
}

options can include start and end values to read a range of bytes from the file instead of the entire file. Both start and end are inclusive and start at 0.

An example to read the last 10 bytes of a file which is 100 bytes long:

fs.createReadStream('sample.txt', {start: 90, end: 99});

fs.WriteStream

WriteStream is a Writable Stream.

Event: 'open'

function (fd) { }

fd is the file descriptor used by the WriteStream.

fs.createWriteStream(path, [options])

Returns a new WriteStream object (See Writable Stream).

options is an object with the following defaults:

{ flags: 'w',
  encoding: null,
  mode: 0666 }

Path

This module contains utilities for dealing with file paths. Userequire('path') to use it. It provides the following methods:

path.normalize(p)

Normalize a string path, taking care of '..' and '.' parts.

When multiple slashes are found, they're replaces by a single one; when the path contains a trailing slash, it is preserved. On windows backslashes are used.

Example:

path.normalize('/foo/bar//baz/asdf/quux/..')
// returns
'/foo/bar/baz/asdf'

path.join([path1], [path2], [...])

Join all arguments together and normalize the resulting path.

Example:

node> require('path').join(
...   '/foo', 'bar', 'baz/asdf', 'quux', '..')
'/foo/bar/baz/asdf'

path.resolve([from ...], to)

Resolves to to an absolute path.

If to isn't already absolute from arguments are prepended in right to left order, until an absolute path is found. If after using all from paths still no absolute path is found, the current working directory is used as well. The resulting path is normalized, and trailing slashes are removed unless the path gets resolved to the root directory.

Another way to think of it is as a sequence of cd commands in a shell.

path.resolve('foo/bar', '/tmp/file/', '..', 'a/../subfile')

Is similar to:

cd foo/bar
cd /tmp/file/
cd ..
cd a/../subfile
pwd

The difference is that the different paths don't need to exist and may also be files.

Examples:

path.resolve('/foo/bar', './baz')
// returns
'/foo/bar/baz'

path.resolve('/foo/bar', '/tmp/file/')
// returns
'/tmp/file'

path.resolve('wwwroot', 'static_files/png/', '../gif/image.gif')
// if currently in /home/myself/node, it returns
'/home/myself/node/wwwroot/static_files/gif/image.gif'

path.dirname(p)

Return the directory name of a path. Similar to the Unix dirname command.

Example:

path.dirname('/foo/bar/baz/asdf/quux')
// returns
'/foo/bar/baz/asdf'

path.basename(p, [ext])

Return the last portion of a path. Similar to the Unix basename command.

Example:

path.basename('/foo/bar/baz/asdf/quux.html')
// returns
'quux.html'

path.basename('/foo/bar/baz/asdf/quux.html', '.html')
// returns
'quux'

path.extname(p)

Return the extension of the path. Everything after the last '.' in the last portion of the path. If there is no '.' in the last portion of the path or the only '.' is the first character, then it returns an empty string. Examples:

path.extname('index.html')
// returns
'.html'

path.extname('index')
// returns
''

path.exists(p, [callback])

Test whether or not the given path exists. Then, call the callback argument with either true or false. Example:

path.exists('/etc/passwd', function (exists) {
  util.debug(exists ? "it's there" : "no passwd!");
});

path.existsSync(p)

Synchronous version of path.exists.

net

The net module provides you with an asynchronous network wrapper. It contains methods for creating both servers and clients (called streams). You can include this module with require("net");

net.createServer([options], [connectionListener])

Creates a new TCP server. The connectionListener argument is automatically set as a listener for the 'connection' event.

options is an object with the following defaults:

{ allowHalfOpen: false
}

If allowHalfOpen is true, then the socket won't automatically send FIN packet when the other end of the socket sends a FIN packet. The socket becomes non-readable, but still writable. You should call the end() method explicitly. See 'end' event for more information.

net.createConnection(arguments...)

Construct a new socket object and opens a socket to the given location. When the socket is established the 'connect' event will be emitted.

The arguments for this method change the type of connection:

net.Server

This class is used to create a TCP or UNIX server.

Here is an example of a echo server which listens for connections on port 8124:

var net = require('net');
var server = net.createServer(function (c) {
  c.write('hello\r\n');
  c.pipe(c);
});
server.listen(8124, 'localhost');

Test this by using telnet:

telnet localhost 8124

To listen on the socket /tmp/echo.sock the last line would just be changed to

server.listen('/tmp/echo.sock');

Use nc to connect to a UNIX domain socket server:

nc -U /tmp/echo.sock

net.Server is an EventEmitter with the following events:

server.listen(port, [host], [callback])

Begin accepting connections on the specified port and host. If thehost is omitted, the server will accept connections directed to any IPv4 address (INADDR_ANY).

This function is asynchronous. The last parameter callback will be called when the server has been bound.

One issue some users run into is getting EADDRINUSE errors. Meaning another server is already running on the requested port. One way of handling this would be to wait a second and the try again. This can be done with

server.on('error', function (e) {
  if (e.code == 'EADDRINUSE') {
    console.log('Address in use, retrying...');
    setTimeout(function () {
      server.close();
      server.listen(PORT, HOST);
    }, 1000);
  }
});

(Note: All sockets in Node are set SO_REUSEADDR already)

server.listen(path, [callback])

Start a UNIX socket server listening for connections on the given path.

This function is asynchronous. The last parameter callback will be called when the server has been bound.

server.listenFD(fd)

Start a server listening for connections on the given file descriptor.

This file descriptor must have already had the bind(2) and listen(2) system calls invoked on it. Additionally, it must be set non-blocking; tryfcntl(fd, F_SETFL, O_NONBLOCK).

server.pause(msecs)

Stop accepting connections for the given number of milliseconds (default is one second). This could be useful for throttling new connections against DoS attacks or other oversubscription.

server.close()

Stops the server from accepting new connections. This function is asynchronous, the server is finally closed when the server emits a 'close'event.

server.address()

Returns the bound address and port of the server as reported by the operating system. Useful to find which port was assigned when giving getting an OS-assigned address. Returns an object with two properties, e.g. {"address":"127.0.0.1", "port":2121}

Example:

var server = net.createServer(function (socket) {
  socket.end("goodbye\n");
});

// grab a random port.
server.listen(function() {
  address = server.address();
  console.log("opened server on %j", address);
});

server.maxConnections

Set this property to reject connections when the server's connection count gets high.

server.connections

The number of concurrent connections on the server.

Event: 'connection'

function (socket) {}

Emitted when a new connection is made. socket is an instance ofnet.Socket.

Event: 'close'

function () {}

Emitted when the server closes.

net.Socket

This object is an abstraction of of a TCP or UNIX socket. net.Socketinstances implement a duplex Stream interface. They can be created by the user and used as a client (with connect()) or they can be created by Node and passed to the user through the 'connection' event of a server.

net.Socket instances are EventEmitters with the following events:

new net.Socket([options])

Construct a new socket object.

options is an object with the following defaults:

{ fd: null
  type: null
  allowHalfOpen: false
}

fd allows you to specify the existing file descriptor of socket. typespecified underlying protocol. It can be 'tcp4', 'tcp6', or 'unix'. About allowHalfOpen, refer to createServer() and 'end' event.

socket.connect(port, [host], [callback])

socket.connect(path, [callback])

Opens the connection for a given socket. If port and host are given, then the socket will be opened as a TCP socket, if host is omitted,localhost will be assumed. If a path is given, the socket will be opened as a unix socket to that path.

Normally this method is not needed, as net.createConnection opens the socket. Use this only if you are implementing a custom Socket or if a Socket is closed and you want to reuse it to connect to another server.

This function is asynchronous. When the 'connect' event is emitted the socket is established. If there is a problem connecting, the 'connect'event will not be emitted, the 'error' event will be emitted with the exception.

The callback parameter will be added as an listener for the 'connect' event.

socket.bufferSize

net.Socket has the property that socket.write() always works. This is to help users get up an running quickly. The computer cannot necessarily keep up with the amount of data that is written to a socket - the network connection simply might be too slow. Node will internally queue up the data written to a socket and send it out over the wire when it is possible. (Internally it is polling on the socket's file descriptor for being writable).

The consequence of this internal buffering is that memory may grow. This property shows the number of characters currently buffered to be written. (Number of characters is approximately equal to the number of bytes to be written, but the buffer may contain strings, and the strings are lazily encoded, so the exact number of bytes is not known.)

Users who experience large or growing bufferSize should attempt to "throttle" the data flows in their program with pause() and resume()`.

socket.setEncoding(encoding=null)

Sets the encoding (either 'ascii', 'utf8', or 'base64') for data that is received.

socket.setSecure()

This function has been removed in v0.3. It used to upgrade the connection to SSL/TLS. See the TLS section for the new API.

socket.write(data, [encoding], [callback])

Sends data on the socket. The second parameter specifies the encoding in the case of a string--it defaults to UTF8 encoding.

Returns true if the entire data was flushed successfully to the kernel buffer. Returns false if all or part of the data was queued in user memory.'drain' will be emitted when the buffer is again free.

The optional callback parameter will be executed when the data is finally written out - this may not be immediately.

socket.write(data, [encoding], [fileDescriptor], [callback])

For UNIX sockets, it is possible to send a file descriptor through the socket. Simply add the fileDescriptor argument and listen for the 'fd'event on the other end.

socket.end([data], [encoding])

Half-closes the socket. I.E., it sends a FIN packet. It is possible the server will still send some data.

If data is specified, it is equivalent to calling socket.write(data, encoding)followed by socket.end().

socket.destroy()

Ensures that no more I/O activity happens on this socket. Only necessary in case of errors (parse error or so).

socket.pause()

Pauses the reading of data. That is, 'data' events will not be emitted. Useful to throttle back an upload.

socket.resume()

Resumes reading after a call to pause().

socket.setTimeout(timeout, [callback])

Sets the socket to timeout after timeout milliseconds of inactivity on the socket. By default net.Socket do not have a timeout.

When an idle timeout is triggered the socket will receive a 'timeout'event but the connection will not be severed. The user must manually end()or destroy() the socket.

If timeout is 0, then the existing idle timeout is disabled.

The optional callback parameter will be added as a one time listener for the 'timeout' event.

socket.setNoDelay(noDelay=true)

Disables the Nagle algorithm. By default TCP connections use the Nagle algorithm, they buffer data before sending it off. Setting noDelay will immediately fire off data each time socket.write() is called.

socket.setKeepAlive(enable=false, [initialDelay])

Enable/disable keep-alive functionality, and optionally set the initial delay before the first keepalive probe is sent on an idle socket. Set initialDelay (in milliseconds) to set the delay between the last data packet received and the first keepalive probe. Setting 0 for initialDelay will leave the value unchanged from the default (or previous) setting.

socket.address()

Returns the bound address and port of the socket as reported by the operating system. Returns an object with two properties, e.g. {"address":"192.168.57.1", "port":62053}

socket.remoteAddress

The string representation of the remote IP address. For example,'74.125.127.100' or '2001:4860:a005::68'.

This member is only present in server-side connections.

Event: 'connect'

function () { }

Emitted when a socket connection successfully is established. See connect().

Event: 'data'

function (data) { }

Emitted when data is received. The argument data will be a Buffer orString. Encoding of data is set by socket.setEncoding(). (See the Readable Stream section for more information.)

Event: 'end'

function () { }

Emitted when the other end of the socket sends a FIN packet.

By default (allowHalfOpen == false) the socket will destroy its file descriptor once it has written out its pending write queue. However, by setting allowHalfOpen == true the socket will not automatically end()its side allowing the user to write arbitrary amounts of data, with the caveat that the user is required to end() their side now.

Event: 'timeout'

function () { }

Emitted if the socket times out from inactivity. This is only to notify that the socket has been idle. The user must manually close the connection.

See also: socket.setTimeout()

Event: 'drain'

function () { }

Emitted when the write buffer becomes empty. Can be used to throttle uploads.

Event: 'error'

function (exception) { }

Emitted when an error occurs. The 'close' event will be called directly following this event.

Event: 'close'

function (had_error) { }

Emitted once the socket is fully closed. The argument had_error is a boolean which says if the socket was closed due to a transmission error.

net.isIP

net.isIP(input)

Tests if input is an IP address. Returns 0 for invalid strings, returns 4 for IP version 4 addresses, and returns 6 for IP version 6 addresses.

net.isIPv4(input)

Returns true if input is a version 4 IP address, otherwise returns false.

net.isIPv6(input)

Returns true if input is a version 6 IP address, otherwise returns false.

UDP / Datagram Sockets

Datagram sockets are available through require('dgram'). Datagrams are most commonly handled as IP/UDP messages but they can also be used over Unix domain sockets.

Event: 'message'

function (msg, rinfo) { }

Emitted when a new datagram is available on a socket. msg is a Buffer and rinfo is an object with the sender's address information and the number of bytes in the datagram.

Event: 'listening'

function () { }

Emitted when a socket starts listening for datagrams. This happens as soon as UDP sockets are created. Unix domain sockets do not start listening until calling bind() on them.

Event: 'close'

function () { }

Emitted when a socket is closed with close(). No new message events will be emitted on this socket.

dgram.createSocket(type, [callback])

Creates a datagram socket of the specified types. Valid types are:udp4, udp6, and unix_dgram.

Takes an optional callback which is added as a listener for message events.

dgram.send(buf, offset, length, path, [callback])

For Unix domain datagram sockets, the destination address is a pathname in the filesystem. An optional callback may be supplied that is invoked after the sendto call is completed by the OS. It is not safe to re-use buf until the callback is invoked. Note that unless the socket is bound to a pathname with bind() there is no way to receive messages on this socket.

Example of sending a message to syslogd on OSX via Unix domain socket /var/run/syslog:

var dgram = require('dgram');
var message = new Buffer("A message to log.");
var client = dgram.createSocket("unix_dgram");
client.send(message, 0, message.length, "/var/run/syslog",
  function (err, bytes) {
    if (err) {
      throw err;
    }
    console.log("Wrote " + bytes + " bytes to socket.");
});

dgram.send(buf, offset, length, port, address, [callback])

For UDP sockets, the destination port and IP address must be specified. A string may be supplied for the address parameter, and it will be resolved with DNS. An optional callback may be specified to detect any DNS errors and when buf may be re-used. Note that DNS lookups will delay the time that a send takes place, at least until the next tick. The only way to know for sure that a send has taken place is to use the callback.

Example of sending a UDP packet to a random port on localhost;

var dgram = require('dgram');
var message = new Buffer("Some bytes");
var client = dgram.createSocket("udp4");
client.send(message, 0, message.length, 41234, "localhost");
client.close();

dgram.bind(path)

For Unix domain datagram sockets, start listening for incoming datagrams on a socket specified by path. Note that clients may send() without bind(), but no datagrams will be received without a bind().

Example of a Unix domain datagram server that echoes back all messages it receives:

var dgram = require("dgram");
var serverPath = "/tmp/dgram_server_sock";
var server = dgram.createSocket("unix_dgram");

server.on("message", function (msg, rinfo) {
  console.log("got: " + msg + " from " + rinfo.address);
  server.send(msg, 0, msg.length, rinfo.address);
});

server.on("listening", function () {
  console.log("server listening " + server.address().address);
})

server.bind(serverPath);

Example of a Unix domain datagram client that talks to this server:

var dgram = require("dgram");
var serverPath = "/tmp/dgram_server_sock";
var clientPath = "/tmp/dgram_client_sock";

var message = new Buffer("A message at " + (new Date()));

var client = dgram.createSocket("unix_dgram");

client.on("message", function (msg, rinfo) {
  console.log("got: " + msg + " from " + rinfo.address);
});

client.on("listening", function () {
  console.log("client listening " + client.address().address);
  client.send(message, 0, message.length, serverPath);
});

client.bind(clientPath);

dgram.bind(port, [address])

For UDP sockets, listen for datagrams on a named port and optional address. Ifaddress is not specified, the OS will try to listen on all addresses.

Example of a UDP server listening on port 41234:

var dgram = require("dgram");

var server = dgram.createSocket("udp4");

server.on("message", function (msg, rinfo) {
  console.log("server got: " + msg + " from " +
    rinfo.address + ":" + rinfo.port);
});

server.on("listening", function () {
  var address = server.address();
  console.log("server listening " +
      address.address + ":" + address.port);
});

server.bind(41234);
// server listening 0.0.0.0:41234

dgram.close()

Close the underlying socket and stop listening for data on it. UDP sockets automatically listen for messages, even if they did not call bind().

dgram.address()

Returns an object containing the address information for a socket. For UDP sockets, this object will contain address and port. For Unix domain sockets, it will contain only address.

dgram.setBroadcast(flag)

Sets or clears the SO_BROADCAST socket option. When this option is set, UDP packets may be sent to a local interface's broadcast address.

dgram.setTTL(ttl)

Sets the IP_TTL socket option. TTL stands for "Time to Live," but in this context it specifies the number of IP hops that a packet is allowed to go through. Each router or gateway that forwards a packet decrements the TTL. If the TTL is decremented to 0 by a router, it will not be forwarded. Changing TTL values is typically done for network probes or when multicasting.

The argument to setTTL() is a number of hops between 1 and 255. The default on most systems is 64.

dgram.setMulticastTTL(ttl)

Sets the IP_MULTICAST_TTL socket option. TTL stands for "Time to Live," but in this context it specifies the number of IP hops that a packet is allowed to go through, specifically for multicast traffic. Each router or gateway that forwards a packet decrements the TTL. If the TTL is decremented to 0 by a router, it will not be forwarded.

The argument to setMulticastTTL() is a number of hops between 0 and 255. The default on most systems is 64.

dgram.setMulticastLoopback(flag)

Sets or clears the IP_MULTICAST_LOOP socket option. When this option is set, multicast packets will also be received on the local interface.

dgram.addMembership(multicastAddress, [multicastInterface])

Tells the kernel to join a multicast group with IP_ADD_MEMBERSHIP socket option.

If multicastInterface is not specified, the OS will try to add membership to all valid interfaces.

dgram.dropMembership(multicastAddress, [multicastInterface])

Opposite of addMembership - tells the kernel to leave a multicast group withIP_DROP_MEMBERSHIP socket option. This is automatically called by the kernel when the socket is closed or process terminates, so most apps will never need to call this.

If multicastInterface is not specified, the OS will try to drop membership to all valid interfaces.

DNS

Use require('dns') to access this module.

Here is an example which resolves 'www.google.com' then reverse resolves the IP addresses which are returned.

var dns = require('dns');

dns.resolve4('www.google.com', function (err, addresses) {
  if (err) throw err;

  console.log('addresses: ' + JSON.stringify(addresses));

  addresses.forEach(function (a) {
    dns.reverse(a, function (err, domains) {
      if (err) {
        console.log('reverse for ' + a + ' failed: ' +
          err.message);
      } else {
        console.log('reverse for ' + a + ': ' +
          JSON.stringify(domains));
      }
    });
  });
});

dns.lookup(domain, family=null, callback)

Resolves a domain (e.g. 'google.com') into the first found A (IPv4) or AAAA (IPv6) record.

The callback has arguments (err, address, family). The address argument is a string representation of a IP v4 or v6 address. The family argument is either the integer 4 or 6 and denotes the family of address (not necessarily the value initially passed to lookup).

dns.resolve(domain, rrtype='A', callback)

Resolves a domain (e.g. 'google.com') into an array of the record types specified by rrtype. Valid rrtypes are A (IPV4 addresses), AAAA (IPV6 addresses), MX (mail exchange records), TXT (text records), SRV (SRV records), PTR (used for reverse IP lookups), NS (name server records) and CNAME (canonical name records).

The callback has arguments (err, addresses). The type of each item in addresses is determined by the record type, and described in the documentation for the corresponding lookup methods below.

On error, err would be an instanceof Error object, where err.errno is one of the error codes listed below and err.message is a string describing the error in English.

dns.resolve4(domain, callback)

The same as dns.resolve(), but only for IPv4 queries (A records).addresses is an array of IPv4 addresses (e.g.['74.125.79.104', '74.125.79.105', '74.125.79.106']).

dns.resolve6(domain, callback)

The same as dns.resolve4() except for IPv6 queries (an AAAA query).

dns.resolveMx(domain, callback)

The same as dns.resolve(), but only for mail exchange queries (MX records).

addresses is an array of MX records, each with a priority and an exchange attribute (e.g. [{'priority': 10, 'exchange': 'mx.example.com'},...]).

dns.resolveTxt(domain, callback)

The same as dns.resolve(), but only for text queries (TXT records).addresses is an array of the text records available for domain (e.g.,['v=spf1 ip4:0.0.0.0 ~all']).

dns.resolveSrv(domain, callback)

The same as dns.resolve(), but only for service records (SRV records).addresses is an array of the SRV records available for domain. Properties of SRV records are priority, weight, port, and name (e.g.,[{'priority': 10, {'weight': 5, 'port': 21223, 'name': 'service.example.com'}, ...]).

dns.reverse(ip, callback)

Reverse resolves an ip address to an array of domain names.

The callback has arguments (err, domains).

dns.resolveNs(domain, callback)

The same as dns.resolve(), but only for name server records (NS records).addresses is an array of the name server records available for domain(e.g., ['ns1.example.com', 'ns2.example.com']).

dns.resolveCname(domain, callback)

The same as dns.resolve(), but only for canonical name records (CNAMErecords). addresses is an array of the canonical name records available fordomain (e.g., ['bar.example.com']).

If there an an error, err will be non-null and an instanceof the Error object.

Each DNS query can return an error code.

HTTP

To use the HTTP server and client one must require('http').

The HTTP interfaces in Node are designed to support many features of the protocol which have been traditionally difficult to use. In particular, large, possibly chunk-encoded, messages. The interface is careful to never buffer entire requests or responses--the user is able to stream data.

HTTP message headers are represented by an object like this:

{ 'content-length': '123',
  'content-type': 'text/plain',
  'connection': 'keep-alive',
  'accept': '*/*' }

Keys are lowercased. Values are not modified.

In order to support the full spectrum of possible HTTP applications, Node's HTTP API is very low-level. It deals with stream handling and message parsing only. It parses a message into headers and body but it does not parse the actual headers or the body.

http.Server

This is an EventEmitter with the following events:

Event: 'request'

function (request, response) { }

Emitted each time there is request. Note that there may be multiple requests per connection (in the case of keep-alive connections).request is an instance of http.ServerRequest and response is an instance of http.ServerResponse

Event: 'connection'

function (socket) { }

When a new TCP stream is established. socket is an object of typenet.Socket. Usually users will not want to access this event. Thestream can also be accessed at request.connection.

Event: 'close'

function (errno) { }

Emitted when the server closes.

Event: 'checkContinue'

function (request, response) { }

Emitted each time a request with an http Expect: 100-continue is received. If this event isn't listened for, the server will automatically respond with a 100 Continue as appropriate.

Handling this event involves calling response.writeContinue if the client should continue to send the request body, or generating an appropriate HTTP response (e.g., 400 Bad Request) if the client should not continue to send the request body.

Note that when this event is emitted and handled, the request event will not be emitted.

Event: 'upgrade'

function (request, socket, head) { }

Emitted each time a client requests a http upgrade. If this event isn't listened for, then clients requesting an upgrade will have their connections closed.

After this event is emitted, the request's socket will not have a dataevent listener, meaning you will need to bind to it in order to handle data sent to the server on that socket.

Event: 'clientError'

function (exception) { }

If a client connection emits an 'error' event - it will forwarded here.

http.createServer([requestListener])

Returns a new web server object.

The requestListener is a function which is automatically added to the 'request' event.

server.listen(port, [hostname], [callback])

Begin accepting connections on the specified port and hostname. If the hostname is omitted, the server will accept connections directed to any IPv4 address (INADDR_ANY).

To listen to a unix socket, supply a filename instead of port and hostname.

This function is asynchronous. The last parameter callback will be called when the server has been bound to the port.

server.listen(path, [callback])

Start a UNIX socket server listening for connections on the given path.

This function is asynchronous. The last parameter callback will be called when the server has been bound.

server.close()

Stops the server from accepting new connections.

http.ServerRequest

This object is created internally by a HTTP server -- not by the user -- and passed as the first argument to a 'request' listener.

This is an EventEmitter with the following events:

Event: 'data'

function (chunk) { }

Emitted when a piece of the message body is received.

Example: A chunk of the body is given as the single argument. The transfer-encoding has been decoded. The body chunk is a string. The body encoding is set withrequest.setEncoding().

Event: 'end'

function () { }

Emitted exactly once for each request. After that, no more 'data' events will be emitted on the request.

Event: 'close'

function (err) { }

Indicates that the underlaying connection was terminated beforeresponse.end() was called or able to flush.

The err parameter is always present and indicates the reason for the timeout:

err.code === 'timeout' indicates that the underlaying connection timed out. This may happen because all incoming connections have a default timeout of 2 minutes.

err.code === 'aborted' means that the client has closed the underlaying connection prematurely.

Just like 'end', this event occurs only once per request, and no more 'data'events will fire afterwards.

Note: 'close' can fire after 'end', but not vice versa.

request.method

The request method as a string. Read only. Example:'GET', 'DELETE'.

request.url

Request URL string. This contains only the URL that is present in the actual HTTP request. If the request is:

GET /status?name=ryan HTTP/1.1\r\n
Accept: text/plain\r\n
\r\n

Then request.url will be:

'/status?name=ryan'

If you would like to parse the URL into its parts, you can userequire('url').parse(request.url). Example:

node> require('url').parse('/status?name=ryan')
{ href: '/status?name=ryan',
  search: '?name=ryan',
  query: 'name=ryan',
  pathname: '/status' }

If you would like to extract the params from the query string, you can use the require('querystring').parse function, or passtrue as the second argument to require('url').parse. Example:

node> require('url').parse('/status?name=ryan', true)
{ href: '/status?name=ryan',
  search: '?name=ryan',
  query: { name: 'ryan' },
  pathname: '/status' }

Read only.

request.trailers

Read only; HTTP trailers (if present). Only populated after the 'end' event.

request.httpVersion

The HTTP protocol version as a string. Read only. Examples:'1.1', '1.0'. Also request.httpVersionMajor is the first integer andrequest.httpVersionMinor is the second.

request.setEncoding(encoding=null)

Set the encoding for the request body. Either 'utf8' or 'binary'. Defaults to null, which means that the 'data' event will emit a Buffer object..

request.pause()

Pauses request from emitting events. Useful to throttle back an upload.

request.resume()

Resumes a paused request.

request.connection

The net.Socket object associated with the connection.

With HTTPS support, use request.connection.verifyPeer() and request.connection.getPeerCertificate() to obtain the client's authentication details.

http.ServerResponse

This object is created internally by a HTTP server--not by the user. It is passed as the second parameter to the 'request' event. It is a Writable Stream.

response.writeContinue()

Sends a HTTP/1.1 100 Continue message to the client, indicating that the request body should be sent. See the checkContinue event onServer.

response.writeHead(statusCode, [reasonPhrase], [headers])

Sends a response header to the request. The status code is a 3-digit HTTP status code, like 404. The last argument, headers, are the response headers. Optionally one can give a human-readable reasonPhrase as the second argument.

Example:

var body = 'hello world';
response.writeHead(200, {
  'Content-Length': body.length,
  'Content-Type': 'text/plain' });

This method must only be called once on a message and it must be called before response.end() is called.

If you call response.write() or response.end() before calling this, the implicit/mutable headers will be calculated and call this function for you.

Note: that Content-Length is given in bytes not characters. The above example works because the string 'hello world' contains only single byte characters. If the body contains higher coded characters then Buffer.byteLength()should be used to determine the number of bytes in a given encoding.

response.statusCode

When using implicit headers (not calling response.writeHead() explicitly), this property controls the status code that will be send to the client when the headers get flushed.

Example:

response.statusCode = 404;

Sets a single header value for implicit headers. If this header already exists in the to-be-sent headers, it's value will be replaced. Use an array of strings here if you need to send multiple headers with the same name.

Example:

response.setHeader("Content-Type", "text/html");

or

response.setHeader("Set-Cookie", ["type=ninja", "language=javascript"]);

Reads out a header that's already been queued but not sent to the client. Note that the name is case insensitive. This can only be called before headers get implicitly flushed.

Example:

var contentType = response.getHeader('content-type');

Removes a header that's queued for implicit sending.

Example:

response.removeHeader("Content-Encoding");

response.write(chunk, encoding='utf8')

If this method is called and response.writeHead() has not been called, it will switch to implicit header mode and flush the implicit headers.

This sends a chunk of the response body. This method may be called multiple times to provide successive parts of the body.

chunk can be a string or a buffer. If chunk is a string, the second parameter specifies how to encode it into a byte stream. By default the encoding is 'utf8'.

Note: This is the raw HTTP body and has nothing to do with higher-level multi-part body encodings that may be used.

The first time response.write() is called, it will send the buffered header information and the first body to the client. The second timeresponse.write() is called, Node assumes you're going to be streaming data, and sends that separately. That is, the response is buffered up to the first chunk of body.

response.addTrailers(headers)

This method adds HTTP trailing headers (a header but at the end of the message) to the response.

Trailers will only be emitted if chunked encoding is used for the response; if it is not (e.g., if the request was HTTP/1.0), they will be silently discarded.

Note that HTTP requires the Trailer header to be sent if you intend to emit trailers, with a list of the header fields in its value. E.g.,

response.writeHead(200, { 'Content-Type': 'text/plain',
                          'Trailer': 'TraceInfo' });
response.write(fileData);
response.addTrailers({'Content-MD5': "7895bf4b8828b55ceaf47747b4bca667"});
response.end();

response.end([data], [encoding])

This method signals to the server that all of the response headers and body has been sent; that server should consider this message complete. The method, response.end(), MUST be called on each response.

If data is specified, it is equivalent to calling response.write(data, encoding)followed by response.end().

http.request(options, callback)

Node maintains several connections per server to make HTTP requests. This function allows one to transparently issue requests.

Options:

http.request() returns an instance of the http.ClientRequestclass. The ClientRequest instance is a writable stream. If one needs to upload a file with a POST request, then write to the ClientRequest object.

Example:

var options = {
  host: 'www.google.com',
  port: 80,
  path: '/upload',
  method: 'POST'
};

var req = http.request(options, function(res) {
  console.log('STATUS: ' + res.statusCode);
  console.log('HEADERS: ' + JSON.stringify(res.headers));
  res.setEncoding('utf8');
  res.on('data', function (chunk) {
    console.log('BODY: ' + chunk);
  });
});

req.on('error', function(e) {
  console.log('problem with request: ' + e.message);
});

// write data to request body
req.write('data\n');
req.write('data\n');
req.end();

Note that in the example req.end() was called. With http.request() one must always call req.end() to signify that you're done with the request - even if there is no data being written to the request body.

If any error is encountered during the request (be that with DNS resolution, TCP level errors, or actual HTTP parse errors) an 'error' event is emitted on the returned request object.

There are a few special headers that should be noted.

http.get(options, callback)

Since most requests are GET requests without bodies, Node provides this convenience method. The only difference between this method and http.request() is that it sets the method to GET and calls req.end() automatically.

Example:

var options = {
  host: 'www.google.com',
  port: 80,
  path: '/index.html'
};

http.get(options, function(res) {
  console.log("Got response: " + res.statusCode);
}).on('error', function(e) {
  console.log("Got error: " + e.message);
});

http.Agent

http.getAgent(host, port)

http.request() uses a special Agent for managing multiple connections to an HTTP server. Normally Agent instances should not be exposed to user code, however in certain situations it's useful to check the status of the agent. The http.getAgent() function allows you to access the agents.

Event: 'upgrade'

function (response, socket, head) { }

Emitted each time a server responds to a request with an upgrade. If this event isn't being listened for, clients receiving an upgrade header will have their connections closed.

A client server pair that show you how to listen for the upgrade event using http.getAgent:

var http = require('http');
var net = require('net');

// Create an HTTP server
var srv = http.createServer(function (req, res) {
  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end('okay');
});
srv.on('upgrade', function(req, socket, upgradeHead) {
  socket.write('HTTP/1.1 101 Web Socket Protocol Handshake\r\n' +
               'Upgrade: WebSocket\r\n' +
               'Connection: Upgrade\r\n' +
               '\r\n\r\n');

  socket.ondata = function(data, start, end) {
    socket.write(data.toString('utf8', start, end), 'utf8'); // echo back
  };
});

// now that server is running
srv.listen(1337, '127.0.0.1', function() {

  // make a request
  var agent = http.getAgent('127.0.0.1', 1337);

  var options = {
    agent: agent,
    port: 1337,
    host: '127.0.0.1',
    headers: {
      'Connection': 'Upgrade',
      'Upgrade': 'websocket'
    }
  };

  var req = http.request(options);
  req.end();

  agent.on('upgrade', function(res, socket, upgradeHead) {
    console.log('got upgraded!');
    socket.end();
    process.exit(0);
  });
});

agent.maxSockets

By default set to 5. Determines how many concurrent sockets the agent can have open.

agent.sockets

An array of sockets currently in use by the Agent. Do not modify.

agent.queue

A queue of requests waiting to be sent to sockets.

http.ClientRequest

This object is created internally and returned from http.request(). It represents an in-progress request whose header has already been queued. The header is still mutable using the setHeader(name, value), getHeader(name),removeHeader(name) API. The actual header will be sent along with the first data chunk or when closing the connection.

To get the response, add a listener for 'response' to the request object.'response' will be emitted from the request object when the response headers have been received. The 'response' event is executed with one argument which is an instance of http.ClientResponse.

During the 'response' event, one can add listeners to the response object; particularly to listen for the 'data' event. Note that the 'response' event is called before any part of the response body is received, so there is no need to worry about racing to catch the first part of the body. As long as a listener for 'data' is added during the 'response'event, the entire body will be caught.

// Good
request.on('response', function (response) {
  response.on('data', function (chunk) {
    console.log('BODY: ' + chunk);
  });
});

// Bad - misses all or part of the body
request.on('response', function (response) {
  setTimeout(function () {
    response.on('data', function (chunk) {
      console.log('BODY: ' + chunk);
    });
  }, 10);
});

This is a Writable Stream.

This is an EventEmitter with the following events:

Event: 'continue'

function () { }

Emitted when the server sends a '100 Continue' HTTP response, usually because the request contained 'Expect: 100-continue'. This is an instruction that the client should send the request body.

Event 'response'

function (response) { }

Emitted when a response is received to this request. This event is emitted only once. Theresponse argument will be an instance of http.ClientResponse.

request.write(chunk, encoding='utf8')

Sends a chunk of the body. By calling this method many times, the user can stream a request body to a server--in that case it is suggested to use the['Transfer-Encoding', 'chunked'] header line when creating the request.

The chunk argument should be an array of integers or a string.

The encoding argument is optional and only applies when chunk is a string.

request.end([data], [encoding])

Finishes sending the request. If any parts of the body are unsent, it will flush them to the stream. If the request is chunked, this will send the terminating '0\r\n\r\n'.

If data is specified, it is equivalent to calling request.write(data, encoding)followed by request.end().

request.abort()

Aborts a request. (New since v0.3.8.)

http.ClientResponse

This object is created when making a request with http.request(). It is passed to the 'response' event of the request object.

The response implements the Readable Stream interface.

Event: 'data'

function (chunk) { }

Emitted when a piece of the message body is received.

Event: 'end'

function () { }

Emitted exactly once for each message. No arguments. After emitted no other events will be emitted on the response.

Event: 'close'

function (err) { }

Indicates that the underlaying connection was terminated beforeend event was emitted. See http.ServerRequest's 'close' event for more information.

response.statusCode

The 3-digit HTTP response status code. E.G. 404.

response.httpVersion

The HTTP version of the connected-to server. Probably either'1.1' or '1.0'. Also response.httpVersionMajor is the first integer andresponse.httpVersionMinor is the second.

The response headers object.

response.trailers

The response trailers object. Only populated after the 'end' event.

response.setEncoding(encoding=null)

Set the encoding for the response body. Either 'utf8', 'ascii', or 'base64'. Defaults to null, which means that the 'data' event will emit a Buffer object..

response.pause()

Pauses response from emitting events. Useful to throttle back a download.

response.resume()

Resumes a paused response.

HTTPS

HTTPS is the HTTP protocol over TLS/SSL. In Node this is implemented as a separate module.

https.Server

This class is a subclass of tls.Server and emits events same ashttp.Server. See http.Server for more information.

https.createServer(options, [requestListener])

Returns a new HTTPS web server object. The options is similer totls.createServer(). The requestListener is a function which is automatically added to the 'request' event.

Example:

// curl -k https://localhost:8000/
var https = require('https');
var fs = require('fs');

var options = {
  key: fs.readFileSync('test/fixtures/keys/agent2-key.pem'),
  cert: fs.readFileSync('test/fixtures/keys/agent2-cert.pem')
};

https.createServer(options, function (req, res) {
  res.writeHead(200);
  res.end("hello world\n");
}).listen(8000);

https.request(options, callback)

Makes a request to a secure web server. Similar options to http.request().

Example:

var https = require('https');

var options = {
  host: 'encrypted.google.com',
  port: 443,
  path: '/',
  method: 'GET'
};

var req = https.request(options, function(res) {
  console.log("statusCode: ", res.statusCode);
  console.log("headers: ", res.headers);

  res.on('data', function(d) {
    process.stdout.write(d);
  });
});
req.end();

req.on('error', function(e) {
  console.error(e);
});

The options argument has the following options

https.get(options, callback)

Like http.get() but for HTTPS.

Example:

var https = require('https');

https.get({ host: 'encrypted.google.com', path: '/' }, function(res) {
  console.log("statusCode: ", res.statusCode);
  console.log("headers: ", res.headers);

  res.on('data', function(d) {
    process.stdout.write(d);
  });

}).on('error', function(e) {
  console.error(e);
});

URL

This module has utilities for URL resolution and parsing. Call require('url') to use it.

Parsed URL objects have some or all of the following fields, depending on whether or not they exist in the URL string. Any parts that are not in the URL string will not be in the parsed object. Examples are shown for the URL

'http://user:[[email protected]](/cdn-cgi/l/email-protection):8080/p/a/t/h?query=string#hash'

The following methods are provided by the URL module:

url.parse(urlStr, parseQueryString=false)

Take a URL string, and return an object. Pass true as the second argument to also parse the query string using the querystring module.

url.format(urlObj)

Take a parsed URL object, and return a formatted URL string.

url.resolve(from, to)

Take a base URL, and a href URL, and resolve them as a browser would for an anchor tag.

Query String

This module provides utilities for dealing with query strings. It provides the following methods:

querystring.stringify(obj, sep='&', eq='=')

Serialize an object to a query string. Optionally override the default separator and assignment characters.

Example:

querystring.stringify({foo: 'bar'})
// returns
'foo=bar'

querystring.stringify({foo: 'bar', baz: 'bob'}, ';', ':')
// returns
'foo:bar;baz:bob'

querystring.parse(str, sep='&', eq='=')

Deserialize a query string to an object. Optionally override the default separator and assignment characters.

Example:

querystring.parse('a=b&b=c')
// returns
{ a: 'b', b: 'c' }

querystring.escape

The escape function used by querystring.stringify, provided so that it could be overridden if necessary.

querystring.unescape

The unescape function used by querystring.parse, provided so that it could be overridden if necessary.

REPL

A Read-Eval-Print-Loop (REPL) is available both as a standalone program and easily includable in other programs. REPL provides a way to interactively run JavaScript and see the results. It can be used for debugging, testing, or just trying things out.

By executing node without any arguments from the command-line you will be dropped into the REPL. It has simplistic emacs line-editing.

mjr:~$ node
Type '.help' for options.
> a = [ 1, 2, 3];
[ 1, 2, 3 ]
> a.forEach(function (v) {
...   console.log(v);
...   });
1
2
3

For advanced line-editors, start node with the environmental variable NODE_NO_READLINE=1. This will start the REPL in canonical terminal settings which will allow you to use with rlwrap.

For example, you could add this to your bashrc file:

alias node="env NODE_NO_READLINE=1 rlwrap node"

repl.start(prompt='> ', stream=process.stdin)

Starts a REPL with prompt as the prompt and stream for all I/O. promptis optional and defaults to > . stream is optional and defaults toprocess.stdin.

Multiple REPLs may be started against the same running instance of node. Each will share the same global object but will have unique I/O.

Here is an example that starts a REPL on stdin, a Unix socket, and a TCP socket:

var net = require("net"),
    repl = require("repl");

connections = 0;

repl.start("node via stdin> ");

net.createServer(function (socket) {
  connections += 1;
  repl.start("node via Unix socket> ", socket);
}).listen("/tmp/node-repl-sock");

net.createServer(function (socket) {
  connections += 1;
  repl.start("node via TCP socket> ", socket);
}).listen(5001);

Running this program from the command line will start a REPL on stdin. Other REPL clients may connect through the Unix socket or TCP socket. telnet is useful for connecting to TCP sockets, and socat can be used to connect to both Unix and TCP sockets.

By starting a REPL from a Unix socket-based server instead of stdin, you can connect to a long-running node process without restarting it.

REPL Features

Inside the REPL, Control+D will exit. Multi-line expressions can be input.

The special variable _ (underscore) contains the result of the last expression.

> [ "a", "b", "c" ]
[ 'a', 'b', 'c' ]
> _.length
3
> _ += 1
4

The REPL provides access to any variables in the global scope. You can expose a variable to the REPL explicitly by assigning it to the context object associated with eachREPLServer. For example:

// repl_test.js
var repl = require("repl"),
    msg = "message";

repl.start().context.m = msg;

Things in the context object appear as local within the REPL:

mjr:~$ node repl_test.js
> m
'message'

There are a few special REPL commands:

Executing JavaScript

You can access this module with:

var vm = require('vm');

JavaScript code can be compiled and run immediately or compiled, saved, and run later.

vm.runInThisContext(code, [filename])

vm.runInThisContext() compiles code as if it were loaded from filename, runs it and returns the result. Running code does not have access to local scope. filename is optional.

Example of using vm.runInThisContext and eval to run the same code:

var localVar = 123,
    usingscript, evaled,
    vm = require('vm');

usingscript = vm.runInThisContext('localVar = 1;',
  'myfile.vm');
console.log('localVar: ' + localVar + ', usingscript: ' +
  usingscript);
evaled = eval('localVar = 1;');
console.log('localVar: ' + localVar + ', evaled: ' +
  evaled);

// localVar: 123, usingscript: 1
// localVar: 1, evaled: 1

vm.runInThisContext does not have access to the local scope, so localVar is unchanged.eval does have access to the local scope, so localVar is changed.

In case of syntax error in code, vm.runInThisContext emits the syntax error to stderr and throws an exception.

vm.runInNewContext(code, [sandbox], [filename])

vm.runInNewContext compiles code to run in sandbox as if it were loaded from filename, then runs it and returns the result. Running code does not have access to local scope and the object sandbox will be used as the global object for code.sandbox and filename are optional.

Example: compile and execute code that increments a global variable and sets a new one. These globals are contained in the sandbox.

var util = require('util'),
    vm = require('vm'),
    sandbox = {
      animal: 'cat',
      count: 2
    };

vm.runInNewContext('count += 1; name = "kitty"', sandbox, 'myfile.vm');
console.log(util.inspect(sandbox));

// { animal: 'cat', count: 3, name: 'kitty' }

Note that running untrusted code is a tricky business requiring great care. To prevent accidental global variable leakage, vm.runInNewContext is quite useful, but safely running untrusted code requires a separate process.

In case of syntax error in code, vm.runInNewContext emits the syntax error to stderr and throws an exception.

vm.createScript(code, [filename])

createScript compiles code as if it were loaded from filename, but does not run it. Instead, it returns a vm.Script object representing this compiled code. This script can be run later many times using methods below. The returned script is not bound to any global object. It is bound before each run, just for that run. filename is optional.

In case of syntax error in code, createScript prints the syntax error to stderr and throws an exception.

script.runInThisContext()

Similar to vm.runInThisContext but a method of a precompiled Script object.script.runInThisContext runs the code of script and returns the result. Running code does not have access to local scope, but does have access to the global object (v8: in actual context).

Example of using script.runInThisContext to compile code once and run it multiple times:

var vm = require('vm');

globalVar = 0;

var script = vm.createScript('globalVar += 1', 'myfile.vm');

for (var i = 0; i < 1000 ; i += 1) {
  script.runInThisContext();
}

console.log(globalVar);

// 1000

script.runInNewContext([sandbox])

Similar to vm.runInNewContext a method of a precompiled Script object.script.runInNewContext runs the code of script with sandbox as the global object and returns the result. Running code does not have access to local scope. sandbox is optional.

Example: compile code that increments a global variable and sets one, then execute this code multiple times. These globals are contained in the sandbox.

var util = require('util'),
    vm = require('vm'),
    sandbox = {
      animal: 'cat',
      count: 2
    };

var script = vm.createScript('count += 1; name = "kitty"', 'myfile.vm');

for (var i = 0; i < 10 ; i += 1) {
  script.runInNewContext(sandbox);
}

console.log(util.inspect(sandbox));

// { animal: 'cat', count: 12, name: 'kitty' }

Note that running untrusted code is a tricky business requiring great care. To prevent accidental global variable leakage, script.runInNewContext is quite useful, but safely running untrusted code requires a separate process.

Child Processes

Node provides a tri-directional popen(3) facility through the ChildProcessclass.

It is possible to stream data through the child's stdin, stdout, andstderr in a fully non-blocking way.

To create a child process use require('child_process').spawn().

Child processes always have three streams associated with them. child.stdin,child.stdout, and child.stderr.

ChildProcess is an EventEmitter.

Event: 'exit'

function (code, signal) {}

This event is emitted after the child process ends. If the process terminated normally, code is the final exit code of the process, otherwise null. If the process terminated due to receipt of a signal, signal is the string name of the signal, otherwise null.

See waitpid(2).

child.stdin

A Writable Stream that represents the child process's stdin. Closing this stream via end() often causes the child process to terminate.

child.stdout

A Readable Stream that represents the child process's stdout.

child.stderr

A Readable Stream that represents the child process's stderr.

child.pid

The PID of the child process.

Example:

var spawn = require('child_process').spawn,
    grep  = spawn('grep', ['ssh']);

console.log('Spawned child pid: ' + grep.pid);
grep.stdin.end();

child_process.spawn(command, args=[], [options])

Launches a new process with the given command, with command line arguments in args. If omitted, args defaults to an empty Array.

The third argument is used to specify additional options, which defaults to:

{ cwd: undefined,
  env: process.env,
  customFds: [-1, -1, -1],
  setsid: false
}

cwd allows you to specify the working directory from which the process is spawned. Use env to specify environment variables that will be visible to the new process. With customFds it is possible to hook up the new process' [stdin, stdout, stderr] to existing streams; -1 means that a new stream should be created. setsid, if set true, will cause the subprocess to be run in a new session.

Example of running ls -lh /usr, capturing stdout, stderr, and the exit code:

var util  = require('util'),
    spawn = require('child_process').spawn,
    ls    = spawn('ls', ['-lh', '/usr']);

ls.stdout.on('data', function (data) {
  console.log('stdout: ' + data);
});

ls.stderr.on('data', function (data) {
  console.log('stderr: ' + data);
});

ls.on('exit', function (code) {
  console.log('child process exited with code ' + code);
});

Example: A very elaborate way to run 'ps ax | grep ssh'

var util  = require('util'),
    spawn = require('child_process').spawn,
    ps    = spawn('ps', ['ax']),
    grep  = spawn('grep', ['ssh']);

ps.stdout.on('data', function (data) {
  grep.stdin.write(data);
});

ps.stderr.on('data', function (data) {
  console.log('ps stderr: ' + data);
});

ps.on('exit', function (code) {
  if (code !== 0) {
    console.log('ps process exited with code ' + code);
  }
  grep.stdin.end();
});

grep.stdout.on('data', function (data) {
  console.log(data);
});

grep.stderr.on('data', function (data) {
  console.log('grep stderr: ' + data);
});

grep.on('exit', function (code) {
  if (code !== 0) {
    console.log('grep process exited with code ' + code);
  }
});

Example of checking for failed exec:

var spawn = require('child_process').spawn,
    child = spawn('bad_command');

child.stderr.setEncoding('utf8');
child.stderr.on('data', function (data) {
  if (/^execvp\(\)/.test(data)) {
    console.log('Failed to start child process.');
  }
});

See also: child_process.exec()

child_process.exec(command, [options], callback)

High-level way to execute a command as a child process, buffer the output, and return it all in a callback.

var util = require('util'),
    exec = require('child_process').exec,
    child;

child = exec('cat *.js bad_file | wc -l',
  function (error, stdout, stderr) {
    console.log('stdout: ' + stdout);
    console.log('stderr: ' + stderr);
    if (error !== null) {
      console.log('exec error: ' + error);
    }
});

The callback gets the arguments (error, stdout, stderr). On success, errorwill be null. On error, error will be an instance of Error and err.codewill be the exit code of the child process, and err.signal will be set to the signal that terminated the process.

There is a second optional argument to specify several options. The default options are

{ encoding: 'utf8',
  timeout: 0,
  maxBuffer: 200*1024,
  killSignal: 'SIGTERM',
  cwd: null,
  env: null }

If timeout is greater than 0, then it will kill the child process if it runs longer than timeout milliseconds. The child process is killed withkillSignal (default: 'SIGTERM'). maxBuffer specifies the largest amount of data allowed on stdout or stderr - if this value is exceeded then the child process is killed.

child.kill(signal='SIGTERM')

Send a signal to the child process. If no argument is given, the process will be sent 'SIGTERM'. See signal(7) for a list of available signals.

var spawn = require('child_process').spawn,
    grep  = spawn('grep', ['ssh']);

grep.on('exit', function (code, signal) {
  console.log('child process terminated due to receipt of signal '+signal);
});

// send SIGHUP to process
grep.kill('SIGHUP');

Note that while the function is called kill, the signal delivered to the child process may not actually kill it. kill really just sends a signal to a process.

See kill(2)

Assert

This module is used for writing unit tests for your applications, you can access it with require('assert').

assert.fail(actual, expected, message, operator)

Throws an exception that displays the values for actual and expected separated by the provided operator.

assert.ok(value, [message])

Tests if value is a true value, it is equivalent to assert.equal(true, value, message);

assert.equal(actual, expected, [message])

Tests shallow, coercive equality with the equal comparison operator ( == ).

assert.notEqual(actual, expected, [message])

Tests shallow, coercive non-equality with the not equal comparison operator ( != ).

assert.deepEqual(actual, expected, [message])

Tests for deep equality.

assert.notDeepEqual(actual, expected, [message])

Tests for any deep inequality.

assert.strictEqual(actual, expected, [message])

Tests strict equality, as determined by the strict equality operator ( === )

assert.notStrictEqual(actual, expected, [message])

Tests strict non-equality, as determined by the strict not equal operator ( !== )

assert.throws(block, [error], [message])

Expects block to throw an error. error can be constructor, regexp or validation function.

Validate instanceof using constructor:

assert.throws(
  function() {
    throw new Error("Wrong value");
  },
  Error
);

Validate error message using RegExp:

assert.throws(
  function() {
    throw new Error("Wrong value");
  },
  /value/
);

Custom error validation:

assert.throws(
  function() {
    throw new Error("Wrong value");
  },
  function(err) {
    if ( (err instanceof Error) && /value/.test(err) ) {
      return true;
    }
  },
  "unexpected error"
);

assert.doesNotThrow(block, [error], [message])

Expects block not to throw an error, see assert.throws for details.

assert.ifError(value)

Tests if value is not a false value, throws if it is a true value. Useful when testing the first argument, error in callbacks.

TTY

Use require('tty') to access this module.

Example:

var tty = require('tty');
tty.setRawMode(true);
process.stdin.resume();
process.stdin.on('keypress', function(char, key) {
  if (key && key.ctrl && key.name == 'c') {
    console.log('graceful exit');
    process.exit()
  }
});

tty.open(path, args=[])

Spawns a new process with the executable pointed to by path as the session leader to a new pseudo terminal.

Returns an array [slaveFD, childProcess]. slaveFD is the file descriptor of the slave end of the pseudo terminal. childProcess is a child process object.

tty.isatty(fd)

Returns true or false depending on if the fd is associated with a terminal.

tty.setRawMode(mode)

mode should be true or false. This sets the properties of the current process's stdin fd to act either as a raw device or default.

tty.setWindowSize(fd, row, col)

ioctls the window size settings to the file descriptor.

tty.getWindowSize(fd)

Returns [row, col] for the TTY associated with the file descriptor.

os Module

Use require('os') to access this module.

os.hostname()

Returns the hostname of the operating system.

os.type()

Returns the operating system name.

os.release()

Returns the operating system release.

os.uptime()

Returns the system uptime in seconds.

os.loadavg()

Returns an array containing the 1, 5, and 15 minute load averages.

os.totalmem()

Returns the total amount of system memory in bytes.

os.freemem()

Returns the amount of free system memory in bytes.

os.cpus()

Returns an array of objects containing information about each CPU/core installed: model, speed (in MHz), and times (an object containing the number of CPU ticks spent in: user, nice, sys, idle, and irq).

Example inspection of os.cpus:

[ { model: 'Intel(R) Core(TM) i7 CPU         860  @ 2.80GHz',
    speed: 2926,
    times:
     { user: 252020,
       nice: 0,
       sys: 30340,
       idle: 1070356870,
       irq: 0 } },
  { model: 'Intel(R) Core(TM) i7 CPU         860  @ 2.80GHz',
    speed: 2926,
    times:
     { user: 306960,
       nice: 0,
       sys: 26980,
       idle: 1071569080,
       irq: 0 } },
  { model: 'Intel(R) Core(TM) i7 CPU         860  @ 2.80GHz',
    speed: 2926,
    times:
     { user: 248450,
       nice: 0,
       sys: 21750,
       idle: 1070919370,
       irq: 0 } },
  { model: 'Intel(R) Core(TM) i7 CPU         860  @ 2.80GHz',
    speed: 2926,
    times:
     { user: 256880,
       nice: 0,
       sys: 19430,
       idle: 1070905480,
       irq: 20 } },
  { model: 'Intel(R) Core(TM) i7 CPU         860  @ 2.80GHz',
    speed: 2926,
    times:
     { user: 511580,
       nice: 20,
       sys: 40900,
       idle: 1070842510,
       irq: 0 } },
  { model: 'Intel(R) Core(TM) i7 CPU         860  @ 2.80GHz',
    speed: 2926,
    times:
     { user: 291660,
       nice: 0,
       sys: 34360,
       idle: 1070888000,
       irq: 10 } },
  { model: 'Intel(R) Core(TM) i7 CPU         860  @ 2.80GHz',
    speed: 2926,
    times:
     { user: 308260,
       nice: 0,
       sys: 55410,
       idle: 1071129970,
       irq: 880 } },
  { model: 'Intel(R) Core(TM) i7 CPU         860  @ 2.80GHz',
    speed: 2926,
    times:
     { user: 266450,
       nice: 1480,
       sys: 34920,
       idle: 1072572010,
       irq: 30 } } ]

Debugger

V8 comes with an extensive debugger which is accessible out-of-process via a simple TCP protocol. Node has a built-in client for this debugger. To use this, start Node with thedebug argument; a prompt will appear:

% node debug myscript.js
debug>

At this point myscript.js is not yet running. To start the script, enter the command run. If everything works okay, the output should look like this:

% node debug myscript.js
debug> run
debugger listening on port 5858
connecting...ok

Node's debugger client doesn't support the full range of commands, but simple step and inspection is possible. By putting the statement debugger;into the source code of your script, you will enable a breakpoint.

For example, suppose myscript.js looked like this:

// myscript.js
x = 5;
setTimeout(function () {
  debugger;
  console.log("world");
}, 1000);
console.log("hello");

Then once the debugger is run, it will break on line 4.

% ./node debug myscript.js
debug> run
debugger listening on port 5858
connecting...ok
hello
break in #<an Object>._onTimeout(), myscript.js:4
  debugger;
  ^
debug> next
break in #<an Object>._onTimeout(), myscript.js:5
  console.log("world");
  ^
debug> print x
5
debug> print 2+2
4
debug> next
world
break in #<an Object>._onTimeout() returning undefined, myscript.js:6
}, 1000);
^
debug> quit
A debugging session is active. Quit anyway? (y or n) y
%

The print command allows you to evaluate variables. The next command steps over to the next line. There are a few other commands available and more to come type help to see others.

Advanced Usage

The V8 debugger can be enabled and accessed either by starting Node with the --debug command-line flag or by signaling an existing Node process with SIGUSR1.

Appendixes

Appendix 1 - Third Party Modules

There are many third party modules for Node. At the time of writing, August 2010, the master repository of modules isthe wiki page.

This appendix is intended as a SMALL guide to new-comers to help them quickly find what are considered to be quality modules. It is not intended to be a complete list. There may be better more complete modules found elsewhere.

Patches to this list are welcome.