Shell special variables: Shell $ 0, $ #, $ *, $ @, $ ?, $$ and command-line parameters
https://www.cnblogs.com/davygeek/p/5670212.html
Monitor whether the process instance does not exist is initiated by the presence of shell scripts
https://www.cnblogs.com/zdz8207/p/3282352.html
SED simple tutorial
https://coolshell.cn/articles/9104.html
Window7 upgrade PowerShell
https://blog.csdn.net/yufumatou/article/details/92766350