Introduction and functions of Linux environment variables

Introduction and function of Linux environment variables

In Linux systems, environment variables are global variables used to store information needed when the system is running, such as program paths. , temporary folders, etc. Environment variables play a very important role in Linux systems and can help users quickly configure and manage the system operating environment. This article will introduce the basic concepts, usage and related code examples of Linux environment variables.

1. Types of environment variables

In the Linux system, there are many different types of environment variables, the most commonly used of which are the following:

1. User Environment variables: Store user-level related configuration information. These environment variables are only valid for the current user and are usually stored in the user's personal configuration file.
2. System environment variables: Store global-level configuration information. These environment variables are valid for all users and are usually stored in system configuration files.
3. Shell environment variables: used to define some configuration information of the Shell, such as the default path of the Shell, prompt, etc.
4. Customized environment variables: Users can customize environment variables to store their own defined related information.

2. Setting and viewing environment variables

In Linux systems, we can use the export command to set environment variables and the echo command to view the values ​​of environment variables. The following are some commonly used methods to set and view environment variables:

1. Set environment variables:

export PATH=$PATH:/usr/local/bin
export JAVA_HOME=/usr/lib/jvm/java-11-openjdk

The above command will add /usr/local/ to the PATH environment variable bin path, and set the JAVA_HOME environment variable to /usr/lib/jvm/java-11-openjdk.

2. View environment variables:

echo $PATH
echo $JAVA_HOME

Use the echo command to view the values ​​of PATH and JAVA_HOME environment variables.

3. The role of environment variables

Environment variables are widely used in Linux systems, mainly including the following aspects:

1. Program execution: environment variables You can specify the path, compiler and other related information when the program is executed to facilitate program running and debugging.
2. User configuration: You can specify the user's default settings through environment variables, such as editor, terminal, etc.
3. System configuration: Various configuration information of the system, such as operating system version, path, etc., can be easily managed through environment variables.

In short, environment variables play a very important role in the Linux system and are one of the foundations of system operation. By properly setting and using environment variables, you can improve system operating efficiency, reduce configuration errors, and improve user experience.

The above is an introduction and introduction to Linux environment variables. I hope it will be helpful to you.

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