通过命令行向shell脚本传递参数
#!/bin/bash

factorial=1
for ((i=1; i<$1; i++))
do
    factorial=$[ $factorial * $i ]
done
echo var: $1, result: $factorial

命令行: ./shell.sh 5  // $1接收了5这个参数

获取参数个数
#!/bin/bash

echo param counts: $#

获取最后一个参数的值
#!/bin/bash

last_param=$#
echo last param: $last_param.
echolast param: ${!#}