Environmental Variables

Environmental variables in Linux are variables that contain information about the system environment, user preferences, or settings. They are used by the operating system and various applications to customize behavior and provide configuration options. Environmental variables are key-value pairs, where the variable name is associated with a specific value.

Here are some important aspects of environmental variables in Linux:

1. System Environmental Variables: These variables are set by the operating system and apply system-wide. They define fundamental aspects of the environment, such as the default shell, system paths, system locale settings, etc. Examples of system environmental variables include PATH, LANG, HOME, and SHELL.

2. User Environmental Variables: These variables are specific to each user and customize the user's environment according to their preferences. They can override or supplement system environmental variables for individual users. User environmental variables can define things like custom paths, default editor, preferred language, and more. Examples of user environmental variables include EDITOR, PS1, DISPLAY, and TZ.

3. Setting Environmental Variables: In Linux, you can set or modify environmental variables using various methods:

   • Exporting variables in the current shell session: You can use the export command followed by the variable name and value to set an environmental variable for the current shell session. For example:

     export MY_VARIABLE="some value"

   • Modifying shell startup files: You can add variable assignments to shell startup files such as ~/.bashrc or ~/.bash_profile to set environmental variables permanently for a specific user. These files are executed each time a user starts a new shell session.

   • Setting system-wide variables: System-wide environmental variables can be defined in configuration files such as /etc/environment, /etc/profile, or files in the /etc/profile.d/ directory. These files are executed during the system startup process and affect all users on the system.

4. Viewing Environmental Variables: To view the currently defined environmental variables, you can use the printenv command or env command. For example:

   printenv
   env

   These commands will display a list of all environmental variables and their respective values.

Environmental variables play a crucial role in configuring and customizing the Linux environment for users and applications. They allow for flexibility and control over various aspects of system behavior and are widely used by scripts, programs, and system administrators to manage and fine-tune the environment.