prefix-cli

What?

Mechanism for prefixing output from multiplexed cli applications

Why?

If you have, for example, a repository hosting a client and api applications, perhaps you'd like to use npm-run-all, particularly run-p to start up all parts of the system, running in parallel. In this case, it gets a little difficult to discern which output is coming from where. To solve this ambiguity, it would be nice if lines from each process' output were prefixed with something easily recognisable. Enter pre

Usage

some-process | pre {label} {color}

where

• label is any text you'd like to prefix lines with
• color is any color understood by chalk
  • color is optional and will default to white

Example please?

prefix-cli installs a cli application, called pre, which will echo any input it receives on stdin with the provided prefix, optionally colored with the provided color. For example, we may have started with a scripts section like this in our package.json:

{
    "scripts": {
        "start-server": "cd server && npm start",
        "start-client": "cd client && npm start"
    }
}

so we install npm-run-all so that we can launch both commands with one script:

{
    "scripts": {
        "start-server": "cd server && npm start",
        "start-client": "cd client && npm start",
        "start": "run-p start-server start-client"
    },
    "devDependencies": {
        "npm-run-all": "^4.1.5"
    }
}

and now our two commands are started simultaneously, with their outputs multiplexed on the terminal. To disambiguate their outputs, we could install and use prefix-cli:

    "scripts": {
        "start-server": "cd server && npm start | pre server yellow",
        "start-client": "cd client && npm start | pre client green",
        "start": "run-p start-server start-client"
    },
    "devDependencies": {
        "npm-run-all": "^4.1.5",
        "prefix-cli": "^1.0.0"
    }

and then we would see lines like:

server > setting up routes
client > packing stuff...
server > listening on port 5000
client > listening on port 3000

This works on the big three platforms (and most likely on others too)