该命令是在node_modules的bin目录下，类似的脚本有cross-env和cross-env-shell,在cross-env脚本中的内容如下:

#!/usr/bin/env node
'use strict';

var crossEnv = require('..');

crossEnv(process.argv.slice(2));

会把node_modules/bin的命令添加到环境变量中，比如:

    "start": "cross-env ESLINT=none PORT=3001  NO_PROXY=true roadhog dev",

而cross-env的功能解决跨平台的环境变量的问题。。

cross-env makes it so you can have a single command without worrying about setting or using the environment variable properly for the platform. Just set it like you would if it's running on a POSIX system, and cross-env will take care of setting it properly.