BASH Environment Variable Description

BASH Path of the BASH executable file
BASH_ENV Path of the BASH environment file, which specifies BASH options
BASH_VERSION Version of BASH
COLUMNS Width, in characters, of console window
EUID Effective user ID
HISTFILE Path of the BASH command history file
HISTFILESIZE Maximum number of lines recorded in history file
HISTSIZE Maximum number of commands recorded in history file
HOME Path of user's home directory
HOSTNAME Name of the host
IFS Field separator (white space) characters
LINES Length, in lines, of console window
LOGNAME User's log in name
LS_COLORS Options for ls command
OSTYPE Operating system name ("Linux")
PATH Program path
PPID Process ID of the shell's parent process
PS1 Command prompt string
PS2 Continuation prompt string
PS4 Execution trace string
PWD Current working directory
SHELL Path of the shell executable
SHLVL Number of nested shell invocations
TERM Terminal type
UID User ID
USER User name


Typical Environment Variables and Their Values

[bmccarty@home bmccarty]$ set
BASH=/bin/bash
BASH_ENV=/home/bmccarty/.bashrc
BASH_VERSION=1.14.7(1)
COLUMNS=85
EUID=2188
HISTFILE=/home/bmccarty/.bash_history
HISTFILESIZE=1000
HISTSIZE=1000
HOME=/home/bmccarty
IFS=
INPUTRC=/etc/inputrc
LINES=49
LOGNAME=bmccarty
LS_COLORS=
OPTERR=1
OPTIND=1
OSTYPE=Linux
PATH=/usr/bin:/bin:/usr/bin:/usr/X11R6/
bin:/usr/local/bin:/home/bmccarty/bin
PPID=26420
PS1=[\u@\h \W]\$
PS2=>
PS4=+
PWD=/home/bmccarty
SHELL=/bin/bash
SHLVL=1
TERM=vt102
UID=2188
USER=bmccarty
USERNAME=
_=bash