To view environment variables, printenv or echo can be used, export can be used for temporary settings, and configuration files need to be modified for permanent settings. The specific steps are: 1. Use printenv or echo $ variable name to view the current variable value; 2. Use export VAR="value" to temporarily set the variable; 3. Write the export command to ~/.bashrc, ~/.bash_profile or /etc/environment to achieve permanent settings; 4. Make the changes take effect through the source file. Common variables such as PATH, HOME, LANG, etc. are used to control command paths, user directories and language settings.
In Linux systems, environment variables are important configurations that affect how the program runs. Viewing and setting them is not complicated, but requires mastering several key commands and methods.
View the current environment variable
The most common method is to use printenv or env command. Both commands can list all currently in effect environment variables. If you only want to view the value of a certain variable, such as PATH , you can write it like this:
printenv PATH
Or use echo :
echo $PATH
This method is suitable for debugging problems, confirming whether a variable is set correctly, or want to understand the current user's environment configuration.
Temporarily set environment variables
If you just want to temporarily set a variable in the current terminal session, you can use export directly:
export MY_VAR="hello"
This variable will be invalid after you close the terminal. Suitable for testing configurations or running certain temporary tasks. It should be noted that the assignment number = there cannot be spaces on both sides, otherwise an error will be reported.
Set environment variables permanently
To make the variable take effect for a long time, the export command needs to be written to the configuration file. Common files include:
-
~/.bashrc: bash shell for the current user -
~/.bash_profile: used to log in to the shell -
/etc/environment: System-level settings (requires administrator permissions)
For example, if you want to permanently add a path to PATH variable, you can add it in ~/.bashrc :
export PATH="/your/custom/path:$PATH"
After saving, run source ~/.bashrc to make the changes take effect immediately.
The configuration files of different distributions and shells may vary slightly. It is recommended to choose the appropriate file according to your situation.
Tips: Common uses of environmental variables
Some variables are often used, such as:
-
PATH: Decide which directories can be executed directly -
HOME: The home directory path of the current user -
LANG: Control language and locale settings -
EDITOR: Specify the default editor, such asvimornano
Understanding the role of these variables will help you better customize your work environment.
Basically that's it. The operation is not complicated, but it is easy to ignore the details, especially the problem of file location and scope of effectiveness.
The above is the detailed content of How to view and set environment variables in Linux?. For more information, please follow other related articles on the PHP Chinese website!
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