linux环境变量设置

参考：linux 环境变量设置方法总结（PATH／LD_LIBRARY_PATH）
https://blog.csdn.net/wangeen/article/details/8159500

查看当前环境变量:
echo $PATH

1,临时修改，当前终端有效
添加库搜索路径
export LD_LIBRARY_PATH=/usr/local/cuda-8.0/lib64

2,用户级别修改
 sudo vi ~/.bashrc
 #export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/cuda-9.0/lib64
 #export PATH=$PATH:/usr/local/cuda-9.0/bin
 export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/cuda-8.0/lib64
 export PATH=$PATH:/usr/local/cuda-8.0/bin
 
 source .bashrc  (source执行刚修改的初始化文件，使之立即生效，而不必注销并重新登录)


3，系统级别修改，针对系统所有用户的全局变量
sudo vi /etc/profile
PATH=/usr/local/cuda-9.0/bin:$PATH
export PATH 
LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/cuda-9.0/lib64
export LD_ LIBRARY_PATH

source /etc/profile   使立即生效