Environment Variable

An environment variable is a variable whose value is set outside the program, typically through functionality built into the operating system or micro-service. An environment variable is made up of a name/value pair, and any number may be created and available for reference at a point in time.

Example of environment variable:

$USER: Gives current user's name.

$PATH: Gives search path for commands.

$PWD: Gives the path of present working directory.

$HOME: Gives path of home directory.

$HOSTNAME: Gives name of the host.

$LANG: Gives the default system language.

$EDITOR: Gives default file editor.

$UID: Gives user ID of current user.

$SHELL: Gives location of current user's shell program.

To Display environment variable:

To see all environment variables:

env

or

printenv

You will find a list of environment variables as below:

SHELL=/bin/bash
SESSION_MANAGER=local/saidul-Inspiron-5502:@/tmp/.ICE-unix/3901,unix/saidul-Inspiron-5502:/tmp/.ICE-unix/3901
QT_ACCESSIBILITY=1
COLORTERM=truecolor
XDG_CONFIG_DIRS=/etc/xdg/xdg-ubuntu:/etc/xdg
XDG_MENU_PREFIX=gnome-
GNOME_DESKTOP_SESSION_ID=this-is-deprecated
LC_ADDRESS=bn_BD
GNOME_SHELL_SESSION_MODE=ubuntu
LC_NAME=bn_BD
................

To Display Value of variable:

Type echo $VARIABLE_NAME as like

echo $PATH

Setting environment variable:

To set a global ENV

 export NAME=Value 

or

set NAME=Value

Example:

export ORACLE_HOME=/home/oracle/app/oracle/product/19.0.0/client_1

See more about setting environment variable

To set a local ENV

To set user wide ENVs

To set system wide ENVs

To unset environment variables

unset NAME

or

NAME=''

Thanks!