1. 查看帮助文档——man man
1 Executable programs or shell commands 2 System calls (functions provided by the kernel) 3 Library calls (functions within program libraries) 4 Special files (usually found in /dev) 5 File formats and conventions eg /etc/passwd 6 Games 7 Miscellaneous (including macro packages and conventions), e.g. man(7), groff(7) 8 System administration commands (usually only for root) 9 Kernel routines [Non standard]
1、2、3、5 需要了解
2. alias 应用别名
3. echo显示一个字符串
echo "hello world"
4.shutdown等关机命令
原文：https://www.cnblogs.com/sailifsh-lyh/p/10811238.html