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This article mainly introduces how to classify linux environment variables, which has certain reference value and can be used for reference by friends who need it. I hope you will learn a lot after reading this article. Next, let the editor take you to learn about it.

Environment variable is a very important concept in Linux. Environment variables can be set by the system, users, Shell, and other programs. A variable is a string that can be assigned, including numbers, text, file names, devices, and other types of data.

Environment variables generally refer to some parameters in the operating system that specify the operating system environment. It is equivalent to a pointer, and to see the value of a variable, you need to add "$".

Classification of environmental variables

According to the scope of action

Variables in Linux can be divided into environment variables and local variables:

1) Environment variables: equivalent to global variables, exist in all Shell and have inheritance

2) Local variables: equivalent to local variables only exist in the current Shell, local variables contain environment variables, and non-environment variables do not have inheritance.

According to the life cycle

1) permanent: the configuration file needs to be modified and the variable takes effect permanently.

2) temporarily: use export definition to disable Shell.

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