node package manager

concurrently

Concurrently

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

Features:

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

Install

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

npm install -g concurrently

or if you are using it from npm scripts:

npm install concurrently --save

Usage

Remember to surround separate commands with quotes, like this:

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\""

Good frontend one-liner example here.

Help:


Usage: concurrently [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
  --kill-others-on-fail            kill other processes if one exits with non zero status code
  --no-color                       disable colors from logging
  -p, --prefix <prefix>            prefix used in logging for each process.
  Possible values: index, pid, time, command, name, none, or a template. Default: index or name (when --names is set). Example template: "{time}-{pid}"

  -n, --names <names>              List of custom names to be used in prefix template.
  Example names: "main,browser,server"

  --name-separator <char>          The character to split <names> on.
  Default: ",". Example usage: concurrently -n "styles,scripts|server" --name-separator "|" <command ...>

  -c, --prefix-colors <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
  Available background colors: bgBlack, bgRed, bgGreen, bgYellow, bgBlue, bgMagenta, bgCyan, bgWhite
  See https://www.npmjs.com/package/chalk for more information.
  Default: "gray.dim". Example: "black.bgWhite,cyan,gray.dim"

  -t, --timestamp-format <format>  specify the timestamp in moment/date-fns format. Default: YYYY-MM-DD HH:mm:ss.SSS

  -r, --raw                        output only raw output of processes, disables prettifying and concurrently coloring
  -s, --success <first|last|all>   Return exit code of zero or one based on the success or failure of the "first" child to terminate, the "last" child, or succeed  only if "all" child processes succeed. Default: all

  -l, --prefix-length <length>     limit how many characters of the command is displayed in prefix.
  The option can be used to shorten long commands.
  Works only if prefix is set to "command". Default: 10

  --allow-restart                  Restart a process which died. Default: false

  --restart-after <miliseconds>    delay time to respawn the process. Default: 0
  
  --restart-tries <times>          limit the number of respawn tries. Default: 1

Examples:

 - Kill other processes if one exits or dies

     $ concurrently --kill-others "grunt watch" "http-server"
     
 - Kill other processes if one exits with non zero status code

     $ concurrently --kill-others-on-fail "npm run build:client" "npm run build:server"

 - 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"

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

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 concurrent to return non-zero exit code too.

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.