$

$HOME
$PATH
$PS1
$HISTFILE
$SHELL

${YourVar}

Variables: Environment variables, env, env-cmd, .env/, SHELL, PS1, HOME, $?, PATH, HISTFILE, PWD, LD_LIBRARY_PATH, printenv, getenv, getenv, direnv, AWS cli environmental variables, envsubst, env:, env_file (docker-compose)