List of Environment variables in Linux

Variable name	Stored information
DISPLAY	used by the X Window system to identify the display server
DOMAIN	domain name
EDITOR	stores your favorite line editor
HISTSIZE	size of the shell history file in number of lines
HOME	path to your home directory
HOSTNAME	local host name
INPUTRC	location of definition file for input devices such as keyboard
LANG	preferred language
LD_LIBRARY_PATH	paths to search for libraries
LOGNAME	login name
MAIL	location of your incoming mail folder
MANPATH	paths to search for man pages
OS	string describing the operating system
OSTYPE	more information about version etc.
PAGER	used by programs like man which need to know what to do in case output is more than one terminal window.
PATH	search paths for commands
PS1	primary prompt
PS2	secondary prompt
PWD	present working directory
SHELL	current shell
TERM	terminal type
UID	user ID
USER(NAME)	user name
VISUAL	your favorite full-screen editor
XENVIRONMENT	location of your personal settings for X behavior
XFILESEARCHPATH	paths to search for graphical libraries