Dấu hiệu phần trăm trong chuỗi vỏ Linux làm gì?

When using the Linux shell, what does the percent sign (%) do? For example:

When the percent sign (%) is used in the pattern ${variable%substring}, it will return content of the variable with the shortest occurrence of substring deleted from the back of the variable.

This function supports wildcard patterns, that is why it accepts an asterisk (star) as a substitute for zero or more characters. It should be mentioned that this is Bash specific. Other Linux shells do not necessarily contain this function.

If you want to learn more about string manipulation in Bash, then I highly suggest reading the following page, Advanced Bash-Scripting Guide: Chapter 10. Manipulating Variables. Among many other handy functions, it explains what a double percent sign (%%) does, for example.

I forgot to mention that when it is used in the pattern $((variable%number)) or $((variable1%$variable2)), the percent sign (%) character will function as a modulo operator.

When the percent sign (%) is used in different contexts, it should be recognized as a regular character only.