Special Variables

  [Shell Vars]    IFS   X LANG   X GLOBIGNORE
  [Shell Options] SHELLOPTS   X BASHOPTS
  [Other Env]     HOME   PATH
  [POSIX Special] $@  $*  $#     $?  $-     $$  $!   $0  $9
  [Other Special] BASH_REMATCH   @PIPESTATUS
  [Platform]      HOSTNAME   OSTYPE
  [Call Stack]    @BASH_SOURCE   @FUNCNAME   @BASH_LINENO   
                  X @BASH_ARGV   X @BASH_ARGC
  [Tracing]       LINENO
  [Process State] X BASHPID   X PPID   UID   EUID   
X [Process Stack] BASH_SUBSHELL   SHLVL
X [Shell State]   BASH_CMDS   @DIRSTACK
  [Completion]    @COMP_WORDS   COMP_CWORD   COMP_LINE   COMP_POINT
                  COMP_WORDBREAKS   @COMPREPLY   X COMP_KEY
                  X COMP_TYPE   COMP_ARGV
  [History]       HISTFILE
  [cd]            PWD   OLDPWD   X CDPATH
  [getopts]       OPTIND   OPTARG   X OPTERR
  [read]          REPLY
  [Functions]     X RANDOM   X SECONDS
