Support cross platform environment variables

Add a cross-env feature which resolves environment variables in a standard way.

Example: I like to use env vars so that configuration information can be stored in package.json. I believe the following will fail on windows but works fine on mac:

  "mkdirs": "dist docs/dist docs/models",
  "scripts": {
    "clean": "shx rm -rf $npm_package_mkdirs && shx mkdir $npm_package_mkdirs",

[frastlin]

Can we just start with node_env? Pretty much every single user of this package will be using node_env sometime in their scripts, and it’s a pain that on OSX and Linux it’s ‘node_env=“production”’ and on Windows it’s ‘set node_env=“production”’. cross-env solves this problem, but I would like a simple solution in shx. Another option is if there are if statements that can run in shx, and you can do one for windows and the other for everything else.

[backspaces]

Nice approach! I may do that.

I use shelljs in nearly all my node utilities. Like the es6 usage, thanks. And didn’t know I could require a json file, that is cool.