shell开发

特殊符号的整理

${var}和$var 取出变量结果
$()和``  在括号中执行命令，且拿到命令的执行结果
() 开启子shell执行命令

示例：

root@VM-12-2-ubuntu:~# name=ezreal
root@VM-12-2-ubuntu:~# echo $name
ezreal
root@VM-12-2-ubuntu:~# echo ${name}
ezreal
root@VM-12-2-ubuntu:~# echo "today is $(date)"
today is Sun May  1 00:13:50 CST 2022
root@VM-12-2-ubuntu:~# echo "today is `date`"
today is Sun May  1 00:13:58 CST 2022
root@VM-12-2-ubuntu:~# (ps; echo $BASH_SUBSHELL;)
  PID TTY          TIME CMD
13781 pts/1    00:00:00 bash
13782 pts/1    00:00:00 ps
32737 pts/1    00:00:00 sudo
32738 pts/1    00:00:00 bash
1

shell数字计算

shell 中常见的算术运算符号

shell 中常见的算术运算命令

双小括号(())