concurrently

What is concurrently?

The 'concurrently' npm package is a utility that allows you to run multiple commands concurrently. It is often used to run multiple processes during development, such as a server and a client application at the same time. It can handle the output of these processes, terminate them all together, and more.

What are concurrently's main functionalities?

Running multiple commands

This feature allows you to run multiple commands at the same time. Each command is quoted and separated by a space.

concurrently "command1 arg" "command2 arg"

Customizing the prefix for command output

This feature allows you to customize the prefix shown in the output for each command. In this example, 'API' and 'UI' are custom prefixes for the two npm scripts.

concurrently --names "API,UI" "npm:api" "npm:start"

Killing all commands when one of them exits

This feature ensures that if one command exits, all other commands are also terminated. This is useful for cleaning up processes if one fails.

concurrently --kill-others "command1" "command2"

Running commands sequentially

This feature allows you to run commands sequentially instead of concurrently. The --success option determines which command's exit code will be used as the exit code for concurrently.

concurrently "command1" "command2" --success first

Other packages similar to concurrently

npm-run-all

A CLI tool to run multiple npm-scripts in parallel or sequential. It is similar to concurrently but specifically designed for npm scripts. It provides a simpler interface for running scripts in series or parallel.

pm2

PM2 is a production process manager for Node.js applications with a built-in load balancer. It is more feature-rich than concurrently, providing a daemon process that helps keep applications alive forever, facilitates common system admin tasks, and can be used in production environments.

foreman

Foreman is a manager for Procfile-based applications. Its focus is on easing the development of applications by allowing you to run multiple processes with a single command. It is not limited to Node.js and can be used with any language or markup.

README

Concurrently

Version: 0.0.2 (previous stable)

Run multiple commands concurrently. Like command1 & command2 but better.

Usage

  Usage: concurrent [options] <command ...>

  Options:

    -h, --help             output usage information
    -V, --version          output the version number
    -k, --kill-others      kill other processes if one exits or dies
    --no-color             disable colors from logging
    -p, --prefix [prefix]  prefix used in logging for each process. Possible values: pid, none, command

  Examples:

   - Kill other processes if one exits or dies

       $ concurrent --kill-others "grunt watch" "http-server"

  For more details, visit https://github.com/kimmobrunfeldt/concurrently

Examples

Run less watch task and watchify with `--kill-others`` option. If one of the processes dies, another is killed too.

concurrent -k "lessc main.less bundle.css" "watchify main.js -o bundle.js"

Install

The tool is written in nodejs, but you can use it to run any commands.

npm install -g concurrently

Why

I like task automation with npm but the suggested way to run multiple commands concurrently is npm run watch-js & npm run watch-css. That's fine but it's hard to keep on track of different outputs. Also if one process fails, others still keep running and you won't even notice the difference.

Another option would be to just run all commands in separate terminals. No thanks.