Linux Setting Environment variables

environment variable Background

Linux is a multi-user operating system, each user logged into the system, there is a dedicated operating environment, usually the default environment variables for each user is the same, users can modify their own environment variables to achieve custom purposes. Environment variables are closely related to the shell, the user login system is to start a shell, for Linux is generally bash, you can reset or switch. Depending on the release, Bash has two basic system-level configuration files:/etc/profile,/ETC/BASHRC. These configuration files contain two different sets of variables: Shell variables and environment variables, shell variables are local, environment variables are global.

setting, using Variables

1 , display environment variables

Echo $PATH

2. Setting and modifying environment variables

Export test_path= "/tmp"

3. Show all environment variables

Env

4. Show locally defined shell variables

Set

5. Set read-only

ReadOnly Test_path

6. Clear Environment variables

Unset Test_path

7. Modify File Settings environment variables

Modify the. bash_profile file, the source command in the user's home directory to make the environment variable effective

Vim ~/.bash_profile & Source ~/.bash_profile

Summary

I. Types of variables

1, Permanent: Modify the configuration file, the permanent effect;

2. Temporary: Export command declaration, close Shell invalidation

Ii. three ways to set up variables

Method	Role user	Effect Aging
Vim/etc/profile & Source	All Users	Permanent effect
Vim ~/.bash_profile & source	Current user	Permanent effect
Export definition Variables	Current Shell	Temporary, disable after shell is closed

Linux Setting Environment variables