8.12 Environment Variables

Shell environment variables provide temporary storage of data and configuration settings. The shell itself sets up a number of environment variables that may be changed by the user to modify the behavior of the shell. A listing of currently defined variables may be obtained using the env command:

$ env

SSH_CONNECTION=192.168.0.19 61231 192.168.0.28 22

MODULES_RUN_QUARANTINE=LD_LIBRARY_PATH

LANG=en_US.UTF-8

HISTCONTROL=ignoredups

HOSTNAME=CentOSFedora-pc.ebookfrenzy.com

XDG_SESSION_ID=15

MODULES_CMD=/usr/share/Modules/libexec/modulecmd.tcl

USER=demo

ENV=/usr/share/Modules/init/profile.sh

SELINUX_ROLE_REQUESTED=

PWD=/home/demo

HOME=/home/demo

SSH_CLIENT=192.168.0.19 61231 22

SELINUX_LEVEL_REQUESTED=

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Perhaps the most useful environment variable is PATH. This defines the directories in which the shell will search for commands entered at the command prompt, and the order in which it will do so. The...