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Appendix B Reference Lists |
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B.3 Built-in Shell Variables
| Variable | Chapter | Meaning |
|---|---|---|
| # | 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. |
| COLUMNS | 3 | Width of display in columns (for editing modes and select ). |
| EDITOR | 2 | Used to set editing mode; also used by mail and other programs. |
| ERRNO | A | Error number of last system call that failed. |
| ENV | 3 | 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. |
| IFS | 7 | 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. |
| MAILPATH | 3 | 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 | 9 | Random number between 0 and 32767 (2215 -1). |
| REPLY | 5,7 | 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. |
| TMOUT | 10 | If set to a positive integer, number of seconds between commands after which shell automatically terminates. |
| VISUAL | 2 | Used to set editing mode. |
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| B.2 Built-in Commands and Keywords | 
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B.4 Test Operators |
