Do NPM packages have to be installed globally to access their functionality via the command line? - bash

Question

I am having trouble understanding how the -g flag works in NPM. Specifically I'm struggling to understand how it relates to command-line functionality exposed by NPM modules.
I assumed that the difference between installing a package locally and globally was simply that a local package would not be available outside of the particular project. And of course that a globally installed package would be available in any project. I'm from a Rails background so this for me would be similar to installing a gem into a particular RVM versus installing it into the global RVM. It would simply affect which places it was available.
However there seems to be more significance than just scope in NPM. For packages that have command-line functionality, like wait-on, the package (as far as I can tell) is not available on the command line unless it's installed globally.
Local install doesn't make the command-line functionality available:
$ npm install wait-on
$ wait-on
=> -bash: /usr/local/bin/wait-on: No such file or directory
Global install does expose the command-line functionality
$ npm install wait-on -g
$ wait-on
=> Usage: wait-on {OPTIONS} resource [...resource]
Description:
wait-on is a command line utility which will wait for files, ports,
sockets, and http(s) resources to become available (or not available
using reverse flag). Exits with success code (0) when all resources
are ready. Non-zero exit code if interrupted or timed out.
Options may also be specified in a config file (js or json). For
example --config configFile.js would result in configFile.js being
required and the resulting object will be merged with any
Can you expose the command-line functionality using a local install?
Is it possible to install locally but also get the command line functionality? This would be very helpful for my CI setup as it's far easier to cache local modules than global modules so where possible I'd prefer to install locally.

Answer 1

If you are using npm 5.2.0 or later, the npx command is included by default. It will allow you to run from the local node modules: npx wait-on
For reference: https://www.npmjs.com/package/npx

Answer 2

I think you can access locally installed modules from the command line only if you add them to your "scripts" section of your package.json. So to use the locally installed version of wait-on, you can add an entry in "scripts" section of package.json like so "wait-on": "wait-on". Then to run it, you would have to do npm run wait-on. You can also do "wo": "wait-on" and then do npm run wo basically meaning what comes after the run is the script entry. In node_modules, there is a .bin folder and inside of this folder is all the executables that you can access this way.

Answer 3

Installing locally makes the package available to the current project (where it stores all of the node modules in node_modules). This is usually only good for using a module like so var module = require('module'); or importing a module.
It will not be available as a command that the shell can resolve until you install it globally npm install -g module where npm will install it in a place where your path variable will resolve this command.
You can find a pretty decent explanation here.
It is also useful to put commands in the scripts block in package.json as it automatically resolve local commands. That means you could have a script that depended on a package without having an undocumented dependency on the same.
If you need to run it locally on cmd, you have to go inside the node_modules and run from the path.