【shell脚本】字符串和数组的使用

#! /bin/bash
username="mayuan"
str_1="hello ${username}"  
str_2='hello ${username}'
echo $str_1  # hello mayuan
echo $str_2  # hello ${username}

#! /bin/bash
username="mayuan"
echo ${#username}  # 6

#! /bin/bash
username="mayuan"
echo ${username:1:3}  # 从第二个字符开始截取3个字符输出"ayu"

#! /bin/bash
username="mayuan"
echo $(expr index "${username}" y)  #查找y在指定字符的位置

#! /bin/bash
arr=(1 2 3 4 5)
echo ${arr[0]} #输出1
echo ${arr[1]} #输出2

#! /bin/bash
arr=(1 2 3 4 5)
echo ${#arr[@]} #输出5
echo ${#arr[*]}