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morgan

(★ 8,200)

HTTP request logger middleware for node.js

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# Installation Guide

1. Get the code

git clone https://github.com/expressjs/morgan

Downloads the entire project code from GitHub to your computer.

cd morgan

Moves into the project folder you just downloaded.

2. Node.js

Easy Recommended

Prerequisites

Git Needed to download the project code from GitHub.
Node.js Node.js must be installed to use npm. The LTS version is recommended.

$ npm install morgan

Downloads and installs the libraries listed in package.json.

✅ After running the command, open the address shown in the terminal (usually something like http://localhost:3000) in your browser.

Pulled directly from this repo's README.

// repository documentation

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# morgan

[![NPM Version][npm-version-image]][npm-url]
[![NPM Downloads][npm-downloads-image]][npm-url]
[![Build Status][ci-image]][ci-url]
[![Coverage Status][coveralls-image]][coveralls-url]

HTTP request logger middleware for node.js

> Named after [Dexter](https://en.wikipedia.org/wiki/Dexter_Morgan), a show you should not watch until completion.

## Installation

This is a [Node.js](https://nodejs.org/en/) module available through the
[npm registry](https://www.npmjs.com/). Installation is done using the
[`npm install` command](https://docs.npmjs.com/getting-started/installing-npm-packages-locally):

```sh
$ npm install morgan
```

## API

```js
var morgan = require('morgan')
```

### morgan(format, options)

Create a new morgan logger middleware function using the given `format` and `options`.
The `format` argument may be a string of a predefined name (see below for the names),
a string of a format string, or a function that will produce a log entry.

The `format` function will be called with three arguments `tokens`, `req`, and `res`,
where `tokens` is an object with all defined tokens, `req` is the HTTP request and `res`
is the HTTP response. The function is expected to return a string that will be the log
line, or `undefined` / `null` to skip logging.

#### Using a predefined format string

```js
morgan('tiny')
```

#### Using format string of predefined tokens

```js
morgan(':method :url :status :res[content-length] - :response-time ms')
```

#### Using a custom format function

``` js
morgan(function (tokens, req, res) {
  return [
    tokens.method(req, res),
    tokens.url(req, res),
    tokens.status(req, res),
    tokens.res(req, res, 'content-length'), '-',
    tokens['response-time'](req, res), 'ms'
  ].join(' ')
})
```

#### Options

Morgan accepts these properties in the options object.

##### immediate

Write log line on request instead of response. This means that a requests will
be logged even if the server crashes, _but data from the response (like the
response code, content length, etc.) cannot be logged_.

##### skip

Function to determine if logging is skipped, defaults to `false`. This function
will be called as `skip(req, res)`.

```js
// EXAMPLE: only log error responses
morgan('combined', {
  skip: function (req, res) { return res.statusCode < 400 }
})
```

##### stream

Output stream for writing log lines, defaults to `process.stdout`.

#### Predefined Formats

There are various pre-defined formats provided:

##### combined

Standard Apache combined log output.
```
:remote-addr - :remote-user [:date[clf]] ":method :url HTTP/:http-version" :status :res[content-length] ":referrer" ":user-agent"
# will output
::1 - - [27/Nov/2024:06:21:42 +0000] "GET /combined HTTP/1.1" 200 2 "-" "curl/8.7.1"
```

##### common

Standard Apache common log output.

```
:remote-addr - :remote-user [:date[clf]] ":method :url HTTP/:http-version" :status :res[content-length]
# will output
::1 - - [27/Nov/2024:06:21:46 +0000] "GET /common HTTP/1.1" 200 2
```

##### dev

Concise output colored by response status for development use. The `:status`
token will be colored green for success codes, red for server error codes,
yellow for client error codes, cyan for redirection codes, and uncolored
for information codes.

```
:method :url :status :response-time ms - :res[content-length]
# will output
GET /dev 200 0.224 ms - 2
```

##### short

Shorter than default, also including response time.

```
:remote-addr :remote-user :method :url HTTP/:http-version :status :res[content-length] - :response-time ms
# will output
::1 - GET /short HTTP/1.1 200 2 - 0.283 ms
```

##### tiny

The minimal output.

```
:method :url :status :res[content-length] - :response-time ms
# will output
GET /tiny 200 2 - 0.188 ms
```

#### Tokens

##### Creating new tokens

To define a token, simply invoke `morgan.token()` with the name and a callback function.
This callback function is expected to return a string value. The value returned is then
available as ":type" in this case:

```js
morgan.token('type', function (req, res) { return req.headers['content-type'] })
```

Calling `morgan.token()` using the same name as an existing token will overwrite that
token definition.

The token function is expected to be called with the arguments `req` and `res`, representing
the HTTP request and HTTP response. Additionally, the token can accept further arguments of
it's choosing to customize behavior.

##### :date[format]

The current date and time in UTC. The available formats are:

- `clf` for the common log format (`"10/Oct/2000:13:55:36 +0000"`)
  - `iso` for the common ISO 8601 date time format (`2000-10-10T13:55:36.000Z`)
  - `web` for the common RFC 1123 date time format (`Tue, 10 Oct 2000 13:55:36 GMT`)

If no format is given, then the default is `web`.

##### :http-version

The HTTP version of the request.

##### :method

The HTTP method of the request.

##### :pid

The process ID of the Node.js process handling the request.

##### :referrer

The Referrer header of the request. This will use the standard mis-spelled Referer header if exists, otherwise Referrer.

##### :remote-addr

The remote address of the request. This will use `req.ip`, otherwise the standard `req.connection.remoteAddress` value (socket address).

##### :remote-user

The user authenticated as part of Basic auth for the request.

##### :req[header]

The given `header` of the request. If the header is not present, the
value will be displayed as `"-"` in the log.

##### :res[header]

The given `header` of the response. If the header is not present, the
value will be displayed as `"-"` in the log.

##### :response-time[digits]

The time between the request coming into `morgan` and when the response
headers are written, in milliseconds.

The `digits` argument is a number that specifies the number of digits to
include on the number, defaulting to `3`, which provides microsecond precision.

##### :status

The status code of the response.

If the request/response cycle completes before a response was sent to the
client (for example, the TCP socket closed prematurely by a client aborting
the request), then the status will be empty (displayed as `"-"` in the log).

##### :total-time[digits]

The time between the request coming into `morgan` and when the response
has finished being written out to the connection, in milliseconds.

The `digits` argument is a number that specifies the number of digits to
include on the number, defaulting to `3`, which provides microsecond precision.

##### :url

The URL of the request. This will use `req.originalUrl` if exists, otherwise `req.url`.

##### :user-agent

The contents of the User-Agent header of the request.

### morgan.compile(format)

Compile a format string into a `format` function for use by `morgan`. A format string
is a string that represents a single log line and can utilize token syntax.
Tokens are references by `:token-name`. If tokens accept arguments, they can
be passed using `[]`, for example: `:token-name[pretty]` would pass the string
`'pretty'` as an argument to the token `token-name`.

The function returned from `morgan.compile` takes three arguments `tokens`, `req`, and
`res`, where `tokens` is object with all defined tokens, `req` is the HTTP request and
`res` is the HTTP response. The function will return a string that will be the log line,
or `undefined` / `null` to skip logging.

Normally formats are defined using `morgan.format(name, format)`, but for certain
advanced uses, this compile function is directly available.

## Examples

### express/connect

Sample app that will log all request in the Apache combined format to STDOUT

```js
var express = require('express')
var morgan = require('morgan')

var app = express()

app.use(morgan('combined'))

app.get('/', function (req, res) {
  res.send('hello, world!')
})
```

### vanilla http server

Sample app that will log all request in the Apache combined format to STDOUT

```js
var finalhandler = require('finalhandler')
var http = require('http')
var morgan = require('morgan')

// create "middleware"
var logger = morgan('combined')

http.createServer(function (req, res) {
  var done = finalhandler(req, res)
  logger(req, res, function (err) {
    if (err) return done(err)

// respond to request
    res.setHeader('content-type', 'text/plain')
    res.end('hello, world!')
  })
})
```

### write logs to a file

#### single file

Sample app that will log all requests in the Apache combined format to the file
`access.log`.

```js
var express = require('express')
var fs = require('fs')
var morgan = require('morgan')
var path = require('path')

var app = express()

// create a write stream (in append mode)
var accessLogStream = fs.createWriteStream(path.join(__dirname, 'access.log'), { flags: 'a' })

// setup the logger
app.use(morgan('combined', { stream: accessLogStream }))

app.get('/', function (req, res) {
  res.send('hello, world!')
})
```

#### log file rotation

Sample app that will log all requests in the Apache combined format to one log
file per day in the `log/` directory using the
[rotating-file-stream module](https://www.npmjs.com/package/rotating-file-stream).

```js
var express = require('express')
var morgan = require('morgan')
var path = require('path')
var rfs = require('rotating-file-stream') // version 2.x

var app = express()

// create a rotating write stream
var accessLogStream = rfs.createStream('access.log', {
  interval: '1d', // rotate daily
  path: path.join(__dirname, 'log')
})

// setup the logger
app.use(morgan('combined', { stream: accessLogStream }))

app.get('/', function (req, res) {
  res.send('hello, world!')
})
```

### split / dual logging

The `morgan` middleware can be used as many times as needed, enabling
combinations like:

* Log entry on request and one on response
  * Log all requests to file, but errors to console
  * ... and more!

Sample app that will log all requests to a file using Apache format, but
error responses are logged to the console:

```js
var express = require('express')
var fs = require('fs')
var morgan = require('morgan')
var path = require('path')

var app = express()

// log only 4xx and 5xx responses to console
app.use(morgan('dev', {
  skip: function (req, res) { return res.statusCode < 400 }
}))

// log all requests to access.log
app.use(morgan('common', {
  stream: fs.createWriteStream(path.join(__dirname, 'access.log'), { flags: 'a' })
}))

app.get('/', function (req, res) {
  res.send('hello, world!')
})
```

### use custom token formats

Sample app that will use custom token formats. This adds an ID to all requests and displays it using the `:id` token.

```js
var express = require('express')
var morgan = require('morgan')
var uuid = require('node-uuid')

morgan.token('id', function getId (req) {
  return req.id
})

var app = express()

app.use(assignId)
app.use(morgan(':id :method :url :response-time'))

app.get('/', function (req, res) {
  res.send('hello, world!')
})

function assignId (req, res, next) {
  req.id = uuid.v4()
  next()
}
```

## License

[MIT](LICENSE)

[ci-image]: https://badgen.net/github/checks/expressjs/morgan/master?label=ci
[ci-url]: https://github.com/expressjs/morgan/actions/workflows/ci.yml
[coveralls-image]: https://badgen.net/coveralls/c/github/expressjs/morgan/master
[coveralls-url]: https://coveralls.io/r/expressjs/morgan?branch=master
[npm-downloads-image]: https://badgen.net/npm/dm/morgan
[npm-url]: https://npmjs.org/package/morgan
[npm-version-image]: https://badgen.net/npm/v/morgan