Sample Environment Variables in bash_profile/bashrc. (See http://scriptingosx.com/2017/04/on-bash-environment-variables/ for details)

.bash_profile

# ENVIRONMENT VARIABLES

# add my ~/bin dir to path
PATH=${PATH}:~/bin
export PATH

# simple prompt
# default macOS prompt is: \h:\W \u\$
export PS1="\W \$ "

# enable Terminal color
export CLICOLOR=1

# set EDITOR to bbedit
if [[ -e "/usr/local/bin/bbedit" ]]; then
    export EDITOR="bbedit -w --resume"
fi