linux shell 条件判断
linux shell if [[ ]]和[ ]区别 || &&
https://blog.csdn.net/whatday/article/details/85028898/
linux之shell命令——条件判断(&& || test)
https://blog.csdn.net/shang_feng_wei/article/details/90378017
https://blog.csdn.net/whatday/article/details/85028898/
https://blog.csdn.net/shang_feng_wei/article/details/90378017