$echo $

$_                           $HISTCMD                     $OPTERR
$BASH                        $HISTCONTROL                 $OPTIND
$BASH_ALIASES                $HISTFILE                    $OSTYPE
$BASH_ARGC                   $HISTFILESIZE                $PATH
$BASH_ARGV                   $HISTSIZE                    $PIPESTATUS
$BASH_CMDS                   $HOME                        $PPID
$BASH_COMMAND                $HOSTNAME                    $PS1
$BASH_COMPLETION             $HOSTTYPE                    $PS2
$BASH_COMPLETION_COMPAT_DIR  $i                           $PS4
$BASH_COMPLETION_DIR         $IFS                         $PWD
$BASH_LINENO                 $L3_HOME                     $RANDOM
$BASHOPTS                    $L3_PARENT_TTY               $_scp_path_esc
$BASHPID                     $L3_SESSION_ID               $SECONDS
$BASH_SOURCE                 $L3_TAMPERED_EDITORS         $SHELL
$BASH_SUBSHELL               $LANG                        $SHELLOPTS
$BASH_VERSINFO               $LANGUAGE                    $SHLVL
$BASH_VERSION                $LINENO                      $SSH_CLIENT
$COLUMNS                     $LINES                       $SSH_CONNECTION
$COMP_WORDBREAKS             $LOGNAME                     $SSH_TTY
$DIRSTACK                    $LS_COLORS                   $TERM
$editor_file                 $MACHTYPE                    $UID
$editor_name                 $MAIL                        $USER
$EUID                        $MAILCHECK
$GROUPS                      $OLDPWD

user