Linux environment variables are dynamic named values that serve as a means to influence the behavior of processes and programs running on a Linux system. They are essentially key-value pairs that store information about the environment in which programs execute.
Linux environment variables are pivotal in configuring and customizing the behavior of various software components. They can determine settings such as the default editor, language preferences, search paths for executable files, and more.
Some essential points about Linux environment variables include:
Global vs. Local Scope: Environment variables can be either global, affecting the entire system, or local, influencing only the current shell session or a specific process.
Common Variables: Several common environment variables are widely used across Linux systems, such as PATH (specifies directories to search for executable files), HOME (points to the current user's home directory), and LANG (determines the default language and localization settings).
Setting Variables: Environment variables can be set, modified, or unset using commands like
export,unset, or by directly assigning values in shell scripts or configuration files.Persistent Configuration: To make environment variables persist across sessions, they can be defined in configuration files like
.bashrc,.profile, or system-wide files in/etc/profile.d/.Interprocess Communication: Environment variables facilitate communication between processes by providing a standardized method for passing configuration or status information.
Customization and Flexibility: Users and administrators can customize the environment variables to tailor the system's behavior according to their preferences, providing a high degree of flexibility.
Examples:
DISPLAY -- the display used by X. This variable is usually set to :0.0, which means the first display on the current computer.
EDITOR -- the user's preferred text editor.
HISTFILESIZE -- the maximum number of lines contained in the history file.
HISTSIZE -- Number of lines added to the history file when the user finish his session
HOME -- your home directory.
HOSTNAME -- the hostname of the computer.
LANG -- your current language.
MAIL -- the location of the user's mail spool. Usually /var/spool/mail/USER.
MANPATH -- the list of directories to search for manual pages.
OSTYPE -- the type of operating system.
PS1 -- the default prompt in bash.
PATH -- stores the path of all the directories which holds binary files you want to execute just by specifying the name of the file and not by relative or absolute path.
PWD -- the current working directory.
SHELL -- the path to the current command shell (for example, /bin/bash).
TERM -- the current terminal type (for example, xterm).
TZ -- your time zone.
USER -- your current username.
Understanding and effectively managing environment variables is crucial for system administrators, developers, and power users to optimize system performance, ensure compatibility, and streamline workflow in Linux environments.