linux环境变量的设置

参考链接：
http://www.powerxing.com/linux-environment-variable/
全局的环境变量存放的文件有：
etc/profile，用户登陆一次，执行一次
etc/bashrc,每打开一次shell，执行一次

/etc/environment - This file is specifically meant for system-wide environment variable settings. It is not a script file, but rather consists of assignment expressions, one per line. Specifically, this file stores the system-wide locale and path settings.
 

/etc/profile - This file gets executed whenever a bash login shell is entered (e.g. when logging in from the console or over ssh), as well as by the DisplayManager when the desktop session loads.