For use during development of a node.js based application.
nodemon will watch the files in the directory where nodemon was started, and if they change, it will automatically restart your node application.
nodemon does not require any changes to your code or method of development. nodemon simply wraps your node application and keeps an eye on any files that have changed. Remember that nodemon is a replacement wrapper for node, think of it as replacing the word "node" on the command line when you run your script.
Either through forking or by using npm (the recommended way):
npm install -g nodemon
And nodemon will be installed in to your bin path. Note that as of npm v1, you must explicitly tell npm to install globally as nodemon is a command line utility.
nodemon wraps your application, so you can pass all the arguments you would normally pass to your app:
nodemon [your node app]
For example, if my application accepted a host and port as the arguments, I would start it as so:
nodemon ./server.js localhost 8080
Any output from this script is prefixed with [nodemon], otherwise all output from your application, errors included, will be echoed out as expected.
nodemon also supports running and monitoring coffee-script apps:
nodemon server.coffee
If no script is given, nodemon will test for a package.json file and if found, will run the file associated with the main property (ref).
You can also pass the debug flag to node through the command line as you would normally:
nodemon --debug ./server.js 80
If you have a package.json file for your app, you can omit the main script entirely and nodemon will read the package.json for the main property and use that value as the app.
nodemon was originally written to restart hanging processes such as web servers, but now supports apps that cleanly exit. If your script exits cleanly, nodemon will continue to monitor the directory (or directories) and restart the script if there are any changes.
Whilst nodemon is running, if you need to manually restart your application, instead of stopping and restarting nodemon, you can simply type rs with a carriage return, and nodemon will restart your process.
nodemon can also be used to execute and monitor other programs. nodemon will read the file extension of the script being run and monitor that extension instead of .js if there's no .nodemonignore:
nodemon --exec "python -v" ./app.py
Now nodemon will run app.py with python in verbose mode (note that if you're not passing args to the exec program, you don't need the quotes), and look for new or modified files with the .py extension.
By default nodemon monitors the current working directory. If you want to take control of that option, use the --watch option to add specific paths:
nodemon --watch app --watch libs app/server.js
Now nodemon will only restart if there are changes in the ./app or ./libs directory. By default nodemon will traverse sub-directories, so there's no need in explicitly including sub-directories.
By default, nodemon looks for files with the .js, .coffee, and .litcoffee extensions. If you use the --exec option and monitor app.py nodemon will monitor files with the extension of .py. However, you can specify your own list with the -e switch like so:
nodemon -e js,css,html
Or with alternative syntax:
nodemon --ext '.js|.css|.html'
Now nodemon will restart on any changes to files in the directory (or subdirectories) with the extensions .js, .css or .html.
In some situations, you may want to wait until a number of files have changed. The timeout before checking for new file changes is 1 second. If you're uploading a number of files and it's taking some number of seconds, this could cause your app to restart multiple times unnecessarily.
To add an extra throttle, or delay restarting, use the --delay command:
nodemon --delay 10 server.js
The delay figure is number of seconds to delay before restarting. So nodemon will only restart your app the given number of seconds after the last file change.
By default, if nodemon will only restart when a .js JavaScript file changes. In some cases you will want to ignore some specific files, directories or file patterns, to prevent nodemon from prematurely restarting your application.
You can use the example ignore file (note that this example file is not hidden - you must rename it to .nodemonignore) as a basis for your nodemon, but it's very simple to create your own:
# this is my ignore file with a nice comment at the top
/vendor/* # ignore all external submodules
/public/* # static files
./README.md # a specific file
*.css # ignore any CSS files too
:(\d)*\.js # monitor javascript files with only digits in their name
The ignore file accepts:
- Comments starting with a
#symbol - Blank lines
- Specific files
- File patterns (this is converted to a regex, so you have full control of the pattern)
- Unescaped regex's begining with
:.
Note the .nodemonignore file is read from the directory you run nodemon from, not from the location of the node script you're running.
nodemon sends a kill signal to your application when it sees a file update. If you need to clean up on shutdown inside your script you can capture the kill signal and handle it yourself.
The following example will listen once for the SIGUSR2 signal (used by nodemon to restart), run the clean up process and then kill itself for nodemon to continue control:
process.once('SIGUSR2', function () {
gracefulShutdown(function () {
process.kill(process.pid, 'SIGUSR2');
})
});
Note that the process.kill is only called once your shutdown jobs are complete. Hat tip to Benjie Gillam for writing technique this up.
Check out the grunt-nodemon plugin to integrate nodemon with the rest of your project's grunt workflow.
nodemon has three potential methods it uses to look for file changes. First, it polls using the find command to search for files modified within the last second. This method works on systems with a BSD based find (Mac, for example).
Next it tries using node's fs.watch. fs.watch will not always work however, and nodemon will try and detect if this is the case by writing a file to the tmp directory and seeing if fs.watch is triggered when it's removed. If nodemon finds that fs.watch was not triggered, it will then fall back to the third method (called legacy watch), which works by statting each file in your working directory looking for changes to the last modified time. This is the most cpu intensive method, but it may be the only option on some systems.
In certain cases, like when where you are working on a different drive than your tmp directory is on, fs.watch may give you a false positive. You can force nodemon to start using the most compatible legacy method by passing the -L switch, e.g. nodemon -L /my/odd/file.js.