linux shell 变量$含义

#!/bin/bash
# $$ Shell本身的PID（ProcessID） 
printf "The complete list is %s\n" "$$"
# $! Shell最后运行的后台Process的PID 
printf "The complete list is %s\n" "$!"
# $? 最后运行的命令的结束代码（返回值） 
printf "The complete list is %s\n" "$?"
# $* 所有参数列表
printf "The complete list is %s\n" "$*"
# $@ 所有参数列表
printf "The complete list is %s\n" "$@"
# $# 添加到Shell的参数个数 
printf "The complete list is %s\n" "$#"
# $0 Shell本身的文件名 
printf "The complete list is %s\n" "$0"
# $1 第一个参数
printf "The complete list is %s\n" "$1"
# $2 第二个参数
printf "The complete list is %s\n" "$2

bash params.sh 123456 QQ

The complete list is 24249
The complete list is
The complete list is 0
The complete list is 123456 QQ
The complete list is 123456
The complete list is QQ
The complete list is 2
The complete list is params.sh
The complete list is 123456
The complete list is QQ