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concurrently
Advanced tools
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.
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
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 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 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.
Run multiple commands concurrently.
Like npm run watch-js & npm run watch-less
but better.
Features:
--kill-others
switch, all commands are killed if one diesThe 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
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"
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
--default-input-target <identifier> 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
Input:
Input can be sent to any of the child processes using either the name or index
of the command followed by a colon. If no child identifier is specified then the
input will be sent to the child specified by the `--default-input-target`
option, which defaults to index 0.
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"
- Shortened NPM run commands
$ concurrently npm:watch-node npm:watch-js npm:watch-css
- Send input to default
$ concurrently "nodemon" "npm run watch-js"
rs # Sends rs command to nodemon process
- Specify a default-input-target
$ concurrently --default-input-target 1 "npm run watch-js" nodemon
rs
- Send input to specific child identified by index
$ concurrently "npm run watch-js" nodemon
1:rs
- Send input to specific child identified by name
$ concurrently -n js,srv "npm run watch-js" nodemon
srv:rs
- Send input to default
$ concurrently "nodemon" "npm run watch-js"
rs # Sends rs command to nodemon process
- Specify a default-input-target
$ concurrently --default-input-target 1 "npm run watch-js" nodemon
rs
- Send input to specific child identified by index
$ concurrently "npm run watch-js" nodemon
1:rs
- Send input to specific child identified by name
$ concurrently -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
$ concurrently npm:watch-*
For more details, visit https://github.com/kimmobrunfeldt/concurrently
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.
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.
FAQs
Run commands concurrently
The npm package concurrently receives a total of 4,266,567 weekly downloads. As such, concurrently popularity was classified as popular.
We found that concurrently demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 2 open source maintainers collaborating on the project.
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