shell：判断某个变量是否包含字符串/变量的方法

笔者在编写shell脚本时遇到一个变量是否包含某个字符的问题，几经百度，发现一个大佬的文章，地址：https://www.cnblogs.com/xiaozhuangAna/p/9726670.html 

所以转载一下。

尝试了有3种方法：

1.使用“=~”符号，注意前后必须要有空格！

** 可以输出正确结果,被匹配的字符串必须要有引号括起来！**

[clouder@ana53 bin]$ a1='hello.world'
[clouder@ana53 bin]$ a2='helloworld'
[clouder@ana53 bin]$ b='.'
[clouder@ana53 bin]$ if [[ ${a1} =~ '.' ]];then echo "yes";else echo "no";fi
yes
[clouder@ana53 bin]$ if [[ ${a2} =~ '.' ]];then echo "yes";else echo "no";fi
no
[clouder@ana53 bin]$ if [[ ${a1} =~ "." ]];then echo "yes";else echo "no";fi
yes
[clouder@ana53 bin]$ if [[ ${a2} =~ "." ]];then echo "yes";else echo "no";fi
no
[clouder@ana53 bin]$ if [[ ${a1} =~ "${b}" ]];then echo "yes";else echo "no";fi
yes
[clouder@ana53 bin]$ if [[ ${a2} =~ "${b}" ]];then echo "yes";else echo "no";fi
no

** 不能输出正确结果 **

[clouder@ana53 bin]$ a1='hello.world'
[clouder@ana53 bin]$ a2='helloworld'
[clouder@ana53 bin]$ b='.'
[clouder@ana53 bin]$ if [[ ${a1} =~ . ]];then echo "yes";else echo "no";fi
yes
[clouder@ana53 bin]$ if [[ ${a2} =~ . ]];then echo "yes";else echo "no";fi
yes
[clouder@ana53 bin]$ if [[ ${a1} =~ ${b} ]];then echo "yes";else echo "no";fi
yes
[clouder@ana53 bin]$ if [[ ${a2} =~ ${b} ]];then echo "yes";else echo "no";fi
yes
[clouder@ana53 bin]$ if [[ ${a1} =~ '${b}' ]];then echo "yes";else echo "no";fi
no
[clouder@ana53 bin]$ if [[ ${a2} =~ '${b}' ]];then echo "yes";else echo "no";fi
no

2.使用”==“加通配符wildcard，注意等号前后必须有空格，注意，通配符跟正则表达式有所区别，*表示匹配 0 或多个字符
可以输出正确结果

[clouder@ana53 bin]$ a1='hello.world'
[clouder@ana53 bin]$ a2='helloworld'
[clouder@ana53 bin]$ if [[ ${a1} == *.* ]];then echo "yes";else echo "no";fi
yes
[clouder@ana53 bin]$ if [[ ${a2} == *.* ]];then echo "yes";else echo "no";fi
no

** 不能输出正确结果 ，通配符不能用括号括起来！**

[clouder@ana53 bin]$ a1='hello.world'
[clouder@ana53 bin]$ a2='helloworld'
[clouder@ana53 bin]$ if [[ ${a2} == "*.*" ]];then echo "yes";else echo "no";fi
no
[clouder@ana53 bin]$ if [[ ${a1} == "*.*" ]];then echo "yes";else echo "no";fi
no
[clouder@ana53 bin]$ if [[ ${a1} == '*.*' ]];then echo "yes";else echo "no";fi
no
[clouder@ana53 bin]$ if [[ ${a2} == '*.*' ]];then echo "yes";else echo "no";fi
no

3.使用echo + grep -q 选项

** 使用这种方法时匹配是否有"."会不正常，所以我们换成匹配普通字符，有没有括号都可以 **

[clouder@ana53 bin]$ a1='hello.world'
[clouder@ana53 bin]$ a2='helloworld'
[clouder@ana53 bin]$ a3="helloworlda"
[clouder@ana53 bin]$ if ( echo ${a1} |grep -q a );then echo "yes";else echo "no";fi
no
[clouder@ana53 bin]$ if ( echo ${a2} |grep -q a );then echo "yes";else echo "no";fi
no
[clouder@ana53 bin]$ if ( echo ${a3} |grep -q a );then echo "yes";else echo "no";fi
yes
[clouder@ana53 bin]$ if ( echo ${a1} |grep -q 'a' );then echo "yes";else echo "no";fi
no
[clouder@ana53 bin]$ if ( echo ${a2} |grep -q 'a' );then echo "yes";else echo "no";fi
no
[clouder@ana53 bin]$ if ( echo ${a3} |grep -q 'a' );then echo "yes";else echo "no";fi
yes
[clouder@ana53 bin]$ if ( echo ${a1} |grep -q "a" );then echo "yes";else echo "no";fi
no
[clouder@ana53 bin]$ if ( echo ${a2} |grep -q "a" );then echo "yes";else echo "no";fi
no
[clouder@ana53 bin]$ if ( echo ${a3} |grep -q "a" );then echo "yes";else echo "no";fi
yes

下面就是笔者的练习

#!/bin/bash

#检查进程是否存在
var=$`lsof -i:443|grep java`
pid_ary=(`ps -ef | grep tomcat | grep java | grep jdk | grep -v grep | awk '{ print $2 }'`)
echo $var

#判断进程是否还有 java和:https信息
if [[ ${var} == *java* ]]
then
	if [[ ${var} == *:https* ]]
	then
		#访问tomcat == 查看tomcat的pid
		
		echo "yes";
	else
		#tomcat进程不存在
		echo "no"
	fi
else
	#tomcat进程不存在
	echo "系统邮箱接受者pop_user为空"
fi

一个小知识点介绍完毕