|#||4||Number of arguments given to current process.|
|-||Options given to shell on invocation.|
|?||5||Exit status of previous command.|
|$||8||Process ID of shell process.|
|_||Last argument to previous command.|
|!||8||Process ID of last background command.|
|CDPATH||3||List of directories for cd command to search.|
Width of display in columns (for editing modes and select).
Used to set editing mode; also used by mail and other programs.
|ERRNO||A||Error number of last system call that failed.|
Name of file to run as environment file when shell is invoked.
|FCEDIT||2||Default editor for fc command.|
|FPATH||4||Search path for autoloaded functions.|
Internal field separator: list of characters that act as word separators. Normally set to SPACE, TAB, and NEWLINE.
|HISTFILE||2||Name of command history file.|
|HISTSIZE||2||Number of lines kept in history file.|
|HOME||3||Home (login) directory.|
|LINENO||9||Number of line in script or function that just ran.|
|LINES||3||Height of display in lines (for select command).|
|3||Name of file to check for new mail.|
|MAILCHECK||3||How often (in seconds) to check for new mail.|
List of file names to check for new mail, if MAIL is not set.
|OLDPWD||3||Previous working directory.|
|OPTARG||6||Argument to option being processed by getopts.|
|OPTIND||6||Number of first argument after options.|
|PATH||3||Search path for commands.|
|PS1||3||Primary command prompt string.|
|PS2||3||Prompt string for line continuations.|
|PS3||5||Prompt string for select command.|
|PS4||9||Prompt string for xtrace option.|
|PPID||8||Process ID of parent process.|
|PWD||3||Current working directory.|
Random number between 0 and 32767 (2215-1).
User's response to select command; result of read command if no variable names given.
|SECONDS||3||Number of seconds since shell was invoked.|
|SHELL||3||Full pathname of shell.|
If set to a positive integer, number of seconds between commands after which shell automatically terminates.
|VISUAL||2||Used to set editing mode.|