1. 字符串分割
${str:startIndex:length}
2.字符索引
expr index ‘c’ $str
3.执行脚本参数
$1 – $9 – The first 9 arguments to the Bash script. (As mentioned above.)
4.参数数量
$# – How many arguments were passed to the Bash script.
5.所有传参名
$@ – All the arguments supplied to the Bash script.
6.字符串长度
${#string} — 获取字符串长度
7.