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

Run multiple commands concurrently. Like npm run watch-js & npm run watch-less but better.

Table of Contents

• concurrently
  • Why
  • Installation
  • Usage
  • API
    • concurrently(commands[, options])
    • Command
    • CloseEvent
  • FAQ

Why

I like task automation with npm but the usual 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. I got tired of opening terminals and made concurrently.

Features:

• Cross platform (including Windows)
• Output is easy to follow with prefixes
• With --kill-others switch, all commands are killed if one dies
• Spawns commands with spawn-command

Installation

concurrently can be installed in the global scope (if you'd like to have it available and use it on the whole system) or locally for a specific package (for example if you'd like to use it in the scripts section of your package):

	npm	Yarn	pnpm	Bun
Global	npm i -g concurrently	yarn global add concurrently	pnpm add -g concurrently	bun add -g concurrently
Local*	npm i -D concurrently	yarn add -D concurrently	pnpm add -D concurrently	bun add -d concurrently

_{* It's recommended to add concurrently to devDependencies as it's usually used for developing purposes. Please adjust the command if this doesn't apply in your case.}

Usage

Note The concurrently command is now also available under the shorthand alias conc.

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

Remember to surround separate commands with quotes:

concurrently "command1 arg" "command2 arg"

Otherwise concurrently would try to run 4 separate commands: command1, arg, command2, arg.

In package.json, escape quotes:

"start": "concurrently \"command1 arg\" \"command2 arg\""

NPM run commands can be shortened:

concurrently "npm:watch-js" "npm:watch-css" "npm:watch-node"

# Equivalent to:
concurrently -n watch-js,watch-css,watch-node "npm run watch-js" "npm run watch-css" "npm run watch-node"

NPM shortened commands also support wildcards. Given the following scripts in package.json:

{
  //...
  "scripts": {
    // ...
    "watch-js": "...",
    "watch-css": "...",
    "watch-node": "..."
    // ...
  }
  // ...
}

concurrently "npm:watch-*"

# Equivalent to:
concurrently -n js,css,node "npm run watch-js" "npm run watch-css" "npm run watch-node"

# Any name provided for the wildcard command will be used as a prefix to the wildcard
# part of the script name:
concurrently -n w: npm:watch-*

# Equivalent to:
concurrently -n w:js,w:css,w:node "npm run watch-js" "npm run watch-css" "npm run watch-node"

Exclusion is also supported. Given the following scripts in package.json:

{
  // ...
  "scripts": {
    "lint:js": "...",
    "lint:ts": "...",
    "lint:fix:js": "...",
    "lint:fix:ts": "..."
    // ...
  }
  // ...
}

# Running only lint:js and lint:ts
#   with lint:fix:js and lint:fix:ts excluded
concurrently "npm:lint:*(!fix)"

Good frontend one-liner example here.

Help:

concurrently [options] <command ...>

General
  -m, --max-processes          How many processes should run at once.
                               Exact number or a percent of CPUs available (for example "50%").
                               New processes only spawn after all restart tries
                               of a process.                            [string]
  -n, --names                  List of custom names to be used in prefix
                               template.
                               Example names: "main,browser,server"     [string]
      --name-separator         The character to split <names> on. Example usage:
                               -n "styles|scripts|server" --name-separator "|"
                                                                  [default: ","]
  -s, --success                Which command(s) must exit with code 0 in order
                               for concurrently exit with code 0 too. Options
                               are:
                               - "first" for the first command to exit;
                               - "last" for the last command to exit;
                               - "all" for all commands;
                               - "command-{name}"/"command-{index}" for the
                               commands with that name or index;
                               - "!command-{name}"/"!command-{index}" for all
                               commands but the ones with that name or index.
                                                                [default: "all"]
  -r, --raw                    Output only raw output of processes, disables
                               prettifying and concurrently coloring.  [boolean]
      --no-color               Disables colors from logging            [boolean]
      --hide                   Comma-separated list of processes to hide the
                               output.
                               The processes can be identified by their name or
                               index.                     [string] [default: ""]
  -g, --group                  Order the output as if the commands were run
                               sequentially.                           [boolean]
      --timings                Show timing information for all processes.
                                                      [boolean] [default: false]
  -P, --passthrough-arguments  Passthrough additional arguments to commands
                               (accessible via placeholders) instead of treating
                               them as commands.      [boolean] [default: false]

Prefix styling
  -p, --prefix            Prefix used in logging for each process.
                          Possible values: index, pid, time, command, name,
                          none, or a template. Example template: "{time}-{pid}"
                         [string] [default: index or name (when --names is set)]
  -c, --prefix-colors     Comma-separated list of chalk colors to use on
                          prefixes. If there are more commands than colors, the
                          last color will be repeated.
                          - Available modifiers: reset, bold, dim, italic,
                          underline, inverse, hidden, strikethrough
                          - Available colors: black, red, green, yellow, blue,
                          magenta, cyan, white, gray,
                          any hex values for colors (e.g. #23de43) or auto for
                          an automatically picked color
                          - Available background colors: bgBlack, bgRed,
                          bgGreen, bgYellow, bgBlue, bgMagenta, bgCyan, bgWhite
                          See https://www.npmjs.com/package/chalk for more
                          information.               [string] [default: "reset"]
  -l, --prefix-length     Limit how many characters of the command is displayed
                          in prefix. The option can be used to shorten the
                          prefix when it is set to "command"
                                                          [number] [default: 10]
  -t, --timestamp-format  Specify the timestamp in moment/date-fns format.
                                   [string] [default: "yyyy-MM-dd HH:mm:ss.SSS"]

Input handling
  -i, --handle-input          Whether input should be forwarded to the child
                              processes. See examples for more information.
                                                                       [boolean]
      --default-input-target  Identifier for child process to which input on
                              stdin should be sent if not specified at start of
                              input.
                              Can be either the index or the name of the
                              process.                              [default: 0]

Killing other processes
  -k, --kill-others          Kill other processes if one exits or dies.[boolean]
      --kill-others-on-fail  Kill other processes if one exits with non zero
                             status code.                              [boolean]
      --kill-signal          Signal to send to other processes if one exits or dies.
                             (SIGTERM/SIGKILL, defaults to SIGTERM)    [string]

Restarting
      --restart-tries  How many times a process that died should restart.
                       Negative numbers will make the process restart forever.
                                                           [number] [default: 0]
      --restart-after  Delay time to respawn the process, in milliseconds.
                                                           [number] [default: 0]

Options:
  -h, --help         Show help                                         [boolean]
  -v, -V, --version  Show version number                               [boolean]


Examples:

 - Output nothing more than stdout+stderr of child processes

     $ concurrently --raw "npm run watch-less" "npm run watch-js"

 - Normal output but without colors e.g. when logging to file

     $ concurrently --no-color "grunt watch" "http-server" > log

 - Custom prefix

     $ concurrently --prefix "{time}-{pid}" "npm run watch" "http-server"

 - Custom names and colored prefixes

     $ concurrently --names "HTTP,WATCH" -c "bgBlue.bold,bgMagenta.bold"
     "http-server" "npm run watch"

 - Auto varying colored prefixes

     $ concurrently -c "auto" "npm run watch" "http-server"

 - Mixing auto and manual colored prefixes

     $ concurrently -c "red,auto" "npm run watch" "http-server" "echo hello"

 - Configuring via environment variables with CONCURRENTLY_ prefix

     $ CONCURRENTLY_RAW=true CONCURRENTLY_KILL_OTHERS=true concurrently "echo
     hello" "echo world"

 - Send input to default

     $ concurrently --handle-input "nodemon" "npm run watch-js"
     rs  # Sends rs command to nodemon process

 - Send input to specific child identified by index

     $ concurrently --handle-input "npm run watch-js" nodemon
     1:rs

 - Send input to specific child identified by name

     $ concurrently --handle-input -n js,srv "npm run watch-js" nodemon
     srv:rs

 - Shortened NPM run commands

     $ concurrently npm:watch-node npm:watch-js npm:watch-css

 - Shortened NPM run command with wildcard (make sure to wrap it in quotes!)

     $ concurrently "npm:watch-*"

 - Exclude patterns so that between "lint:js" and "lint:fix:js", only "lint:js"
 is ran

     $ concurrently "npm:*(!fix)"

 - Passthrough some additional arguments via '{<number>}' placeholder

     $ concurrently -P "echo {1}" -- foo

 - Passthrough all additional arguments via '{@}' placeholder

     $ concurrently -P "npm:dev-* -- {@}" -- --watch --noEmit

 - Passthrough all additional arguments combined via '{*}' placeholder

     $ concurrently -P "npm:dev-* -- {*}" -- --watch --noEmit

For more details, visit https://github.com/open-cli-tools/concurrently

API

concurrently can be used programmatically by using the API documented below:

concurrently(commands[, options])

• commands: an array of either strings (containing the commands to run) or objects with the shape { command, name, prefixColor, env, cwd }.

• options (optional): an object containing any of the below:

  • cwd: the working directory to be used by all commands. Can be overriden per command. Default: process.cwd().
  • defaultInputTarget: the default input target when reading from inputStream. Default: 0.
  • handleInput: when true, reads input from process.stdin.
  • inputStream: a Readable stream to read the input from. Should only be used in the rare instance you would like to stream anything other than process.stdin. Overrides handleInput.
  • pauseInputStreamOnFinish: by default, pauses the input stream (process.stdin when handleInput is enabled, or inputStream if provided) when all of the processes have finished. If you need to read from the input stream after concurrently has finished, set this to false. (#252).
  • killOthers: an array of exitting conditions that will cause a process to kill others. Can contain any of success or failure.
  • maxProcesses: how many processes should run at once.
  • outputStream: a Writable stream to write logs to. Default: process.stdout.
  • prefix: the prefix type to use when logging processes output. Possible values: index, pid, time, command, name, none, or a template (eg [{time} process: {pid}]). Default: the name of the process, or its index if no name is set.
  • prefixColors: a list of colors as supported by chalk or auto for an automatically picked color. If concurrently would run more commands than there are colors, the last color is repeated, unless if the last color value is auto which means following colors are automatically picked to vary. Prefix colors specified per-command take precedence over this list.
  • prefixLength: how many characters to show when prefixing with command. Default: 10
  • raw: whether raw mode should be used, meaning strictly process output will be logged, without any prefixes, coloring or extra stuff. Can be overriden per command.
  • successCondition: the condition to consider the run was successful. If first, only the first process to exit will make up the success of the run; if last, the last process that exits will determine whether the run succeeds. Anything else means all processes should exit successfully.
  • restartTries: how many attempts to restart a process that dies will be made. Default: 0.
  • restartDelay: how many milliseconds to wait between process restarts. Default: 0.
  • timestampFormat: a date-fns format to use when prefixing with time. Default: yyyy-MM-dd HH:mm:ss.ZZZ
  • additionalArguments: list of additional arguments passed that will get replaced in each command. If not defined, no argument replacing will happen.

Returns: an object in the shape { result, commands }.

• result: a Promise that resolves if the run was successful (according to successCondition option), or rejects, containing an array of CloseEvent, in the order that the commands terminated.
• commands: an array of all spawned Commands.

Example:

const concurrently = require('concurrently');
const { result } = concurrently(
  [
    'npm:watch-*',
    { command: 'nodemon', name: 'server' },
    { command: 'deploy', name: 'deploy', env: { PUBLIC_KEY: '...' } },
    {
      command: 'watch',
      name: 'watch',
      cwd: path.resolve(__dirname, 'scripts/watchers'),
    },
  ],
  {
    prefix: 'name',
    killOthers: ['failure', 'success'],
    restartTries: 3,
    cwd: path.resolve(__dirname, 'scripts'),
  }
);
result.then(success, failure);

Command

An object that contains all information about a spawned command, and ways to interact with it.
It has the following properties:

• index: the index of the command among all commands spawned.
• command: the command line of the command.
• name: the name of the command; defaults to an empty string.
• cwd: the current working directory of the command.
• env: an object with all the environment variables that the command will be spawned with.
• killed: whether the command has been killed.
• exited: whether the command exited yet.
• pid: the command's process ID.
• stdin: a Writable stream to the command's stdin.
• stdout: an RxJS observable to the command's stdout.
• stderr: an RxJS observable to the command's stderr.
• error: an RxJS observable to the command's error events (e.g. when it fails to spawn).
• timer: an RxJS observable to the command's timing events (e.g. starting, stopping).
• close: an RxJS observable to the command's close events. See CloseEvent for more information.
• start(): starts the command, setting up all
• kill([signal]): kills the command, optionally specifying a signal (e.g. SIGTERM, SIGKILL, etc).

CloseEvent

An object with information about a command's closing event.
It contains the following properties:

• command: a stripped down version of Command, including only name, command, env and cwd properties.
• index: the index of the command among all commands spawned.
• killed: whether the command exited because it was killed.
• exitCode: the exit code of the command's process, or the signal which it was killed with.
• timings: an object in the shape { startDate, endDate, durationSeconds }.

FAQ

• Process exited with code null?

  From Node child_process documentation, exit event:

  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.

  So null means the process didn't terminate normally. This will make concurrently to return non-zero exit code too.

• Does this work with the npm-replacements yarn, pnpm, or Bun?

  Yes! In all examples above, you may replace "npm" with "yarn", "pnpm", or "bun".