# 判断字符串包含关系的方法

在shell中经常需要判断字符串是否包含在另一个字符串中，以下是搜集的一些shell处理方法：

* 利用grep查找

```bash
strA="long string"
strB="string"
result=$(echo $strA | grep "${strB}")
if [[ "$result" != "" ]]
then
    echo "包含"
else
    echo "不包含"
fi
```

`grep` 查找要搜索的字符串，用变量`result`记录结果。如果结果不为空，说明strA包含strB。如果结果为空，说明不包含。

* 利用字符串运算符 (这个方法最简洁)

```bash
strA="helloworld"
strB="low"
if [[ $strA =~ $strB ]]
then
    echo "包含"
else
    echo "不包含"
fi
```

字符串运算符 `=~` 直接判断strA是否包含strB，要求bash版本3.x（不过，现在主流操作系统都满足要求）。

* 利用通配符

```bash
A="helloworld"
B="low"
if [[ $A == *$B* ]]
then
    echo "包含"
else
    echo "不包含"
fi
```

* 利用case in 语句

```bash
thisString="1 2 3 4 5" # 源字符串
searchString="1 2" # 搜索字符串
case $thisString in 
    *"$searchString"*) echo Enemy Spot ;;
    *) echo nope ;;
esa
```

* 利用替换

```bash
STRING_A=$1
STRING_B=$2
if [[ ${STRING_A/${STRING_B}//} == $STRING_A ]]
    then
        ## is not substring.
        echo N
        return 0
    else
        ## is substring.
        echo Y
        return 1
fi
```

## 参考

* [Shell判断字符串包含关系的几种方法](http://blog.csdn.net/iamlihongwei/article/details/59484029)


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://huataihuang.gitbook.io/cloud-atlas-draft/develop/shell/bash/check_string_include.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.