Linux Shell判断字符串是否存在包含关系

在Pyhton里判断字符串是否存在包含关系非常简单，只要if a in b就行了，但如何在Shell中判断字符串的包含关系呢？

#! /bin/bash

var1="hello"
var2="he"

#方法1
if [ ${var1:0:2} = $var2 ]; then
    echo "1:include"
fi

#方法2
echo "$var1" | grep -q "$var2"
if [ $? -eq 0 ]; then
    echo "2:include"
fi

#方法3
echo "$var1" |grep -q "$var2" && echo "include" ||echo "not"

#方法4
[[ "${var1/$var2/}" != "$var2" ]] && echo "include" || echo "not"

其他方法：
expr或awk的index函数
${var#...}                  
${var%...}
${var/.../...}