[Linux 常見問題] Bash - How to check if a string contains a substring in Bash

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Question
I have a string in Bash:

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1. string="My string"  

How can I test if it contains another string?

HowTo
You can use Marcus's answer (* wildcards) outside a case statement, too, if you use double brackets:

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1. string='My long string'  
2. if [[ $string == *"My long"* ]]; then  
3.   echo "It's there!"  
4. fi  

Note that spaces in the needle string need to be placed between double quotes, and the * wildcards should be outside. Also note that a simple comparison operator is used (i.e. ==), not the regex operator =~.