| $BASH_ENV |
absolute path of startup file |
| $CDPATH |
directories searched by cd |
| $FCEDIT |
absolute path of history editor |
| $HISTCMD |
the history number of the current command |
| $HISFILE |
absolute path of history file |
| $HISTSIZE |
number of remembered commands |
| $HOME |
login directory |
| $IFS |
token delimiters |
| $LINENO |
current line number in shell script |
| $LINES |
terminal height |
| $MAIL |
absolute path of mailbox |
| $MAILCHECK |
number of seconds to check mail |
| $OLDPWD |
absolute path of previous directory |
| $OPTARG |
option set by getopt |
| $OPTIND |
option's ordinal position set by getopt |
| $OSTYPE |
the OS on which bash is executing |
| $PATH |
command search path |
| $PPID |
process ID of parent |
| $PS1 |
primary prompt |
| $PS2 |
secondary prompt |
| $PWD |
absolute path of current directory |
| $RANDOM |
random integer |
| $REPLY |
default variable for read |
| $SECONDS |
number of seconds since shell started |
| $SHELL |
absolute pathname of preferred shell |
| $TMOUT |
seconds to log out after lack of use |
| $UID |
user ID of the current user |
| $$ |
process ID of current shell |
| $? |
exit status of most recent statement |
| $# |
參數的數目 |
| $* |
代表所有參數 |
| $! |
PID of the most recently started backgroup job |
