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| PS3 | The value of this parameter is used as the prompt for the select command. (See "Shell Grammar," earlier in this manual page.) |
| PS4 | The value of this parameter is expanded and the value is printed before each command bash displays during an execution trace. The first character of PS4 is replicated multiple times, as necessary, to indicate multiple levels of indirection. The default is +. |
| HISTSIZE | The number of commands to remember in the command history, (See "History," later in this manual page.) The default value is 500. |
| HISTFILE | The name of the file in which command history is saved. (See "History.") The default value is ~/.bash_history. If unset, the command history is not saved when an interactive shell exits. |
| HISTFILESIZE | The maximum number of lines contained in the history file. When this variable is assigned a value, the history file is truncated, if necessary, to contain no more than that number of lines. The default value is 500. |
| OPTERR | If set to the value 1, bash displays error messages generated by the getopts built-in command. (See "Shell Built-in Commands."). OPTERR is initialized to 1 each time the shell is invoked or a shell script is executed. |
| PROMPT_COMMAND | If set, the value is executed as a command prior to issuing each primary prompt. |
| IGNOREEOF | Controls the action of the shell on receipt of an EOF character as the sole input. If set, the value is the number of consecutive EOF characters typed as the first characters on an input line before bash exits. If the variable exists but does not have a numeric value, or has no value, the default value is 10. If it does not exist, EOF signifies the end of input to the shell. This is only in effect for interactive shells. |
| TMOUT | If set to a value greater than zero, the value is interpreted as the number of seconds to wait for input after issuing the primary prompt. bash terminates after waiting for that number of seconds if input does not arrive. |
| FCEDIT | The default editor for the fc built-in command. |
| FIGNORE | A colon-separated list of suffixes to ignore when performing filename completion. (See "Readline," later in this manual page.) A filename whose suffix matches one of the entries in FIGNORE is excluded from the list of matched filenames. A sample value is .o:~. |
| INPUTRC | The filename for the readline startup file, overriding the default of ~/.inputrc. (See "Readline.") |
| notify | If set, bash reports terminated background jobs immediately, rather than waiting until before printing the next primary prompt. (See also the _b option to the set built-in command.) |
| history_control HISTCONTROL | If set to a value of ignorespace, lines that begin with a space character are not entered on the history list. If set to a value of ignoredups, lines matching the last history line are not entered. A value of ignoreboth combines the two options. If unset, or if set to any other value than the preceding, all lines read by the parser are saved on the history list. |
| command_oriented_history | If set, bash attempts to save all lines of a multiple_line command in the same history entry. This allows easy reediting of multiline commands. |
| glob_dot_filenames | If set, bash includes filenames beginning with a period (.) in the results of pathname expansion. |
| allow-null_glob_expansion | If set, bash allows pathname patterns which match no files (see "Pathname Expansion") to expand to a null string, rather than themselves. |
| histchars | The two or three characters that control history expansion and tokenization. (See "History Expansion," later in this manual page.) The first character is the history expansion character; that is, the character that signals the start of a history expansion, |