|GNU Bash Reference Manual|
by Chet Ramey and Brian Fox
Paperback (6"x9"), 180 pages
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"An essential resource .... the most detailed coverage available for all aspects of Bash" --- Linux User and Developer Magazine (Issue 37, Mar 2004) Get a printed copy>>>
8.3.1 Readline Init File Syntax
There are only a few basic constructs allowed in the Readline init file. Blank lines are ignored. Lines beginning with a ‘#’ are comments. Lines beginning with a ‘$’ indicate conditional constructs (see section 8.3.2 Conditional Init Constructs). Other lines denote variable settings and key bindings.
- Variable Settings
You can modify the run-time behavior of Readline by
altering the values of variables in Readline
setcommand within the init file. The syntax is simple:
set variable valueHere, for example, is how to change from the default Emacs-like key binding to use
viline editing commands:
set editing-mode viVariable names and values, where appropriate, are recognized without regard to case. Unrecognized variable names are ignored. Boolean variables (those that can be set to on or off) are set to on if the value is null or empty, on (case-insensitive), or 1. Any other value results in the variable being set to off. The
bind -Vcommand lists the current Readline variable names and values. See section 4.2 Bash Builtin Commands. A great deal of run-time behavior is changeable with the following variables.
- Controls what happens when Readline wants to ring the terminal bell. If set to ‘none’, Readline never rings the bell. If set to ‘visible’, Readline uses a visible bell if one is available. If set to ‘audible’ (the default), Readline attempts to ring the terminal's bell.
- If set to ‘on’, Readline attempts to bind the control characters treated specially by the kernel's terminal driver to their Readline equivalents.
The string to insert at the beginning of the line when the
insert-commentcommand is executed. The default value is
- If set to ‘on’, Readline performs filename matching and completion in a case-insensitive fashion. The default value is ‘off’.
The number of possible completions that determines when the user is
asked whether the list of possibilities should be displayed.
If the number of possible completions is greater than this value,
Readline will ask the user whether or not he wishes to view
them; otherwise, they are simply listed.
This variable must be set to an integer value greater than or equal to 0.
A negative value means Readline should never ask.
The default limit is
- If set to ‘on’, Readline will convert characters with the eighth bit set to an ASCII key sequence by stripping the eighth bit and prefixing an ESC character, converting them to a meta-prefixed key sequence. The default value is ‘on’.
If set to ‘On’, Readline will inhibit word completion.
Completion characters will be inserted into the line as if they had
been mapped to
self-insert. The default is ‘off’.
editing-modevariable controls which default set of key bindings is used. By default, Readline starts up in Emacs editing mode, where the keystrokes are most similar to Emacs. This variable can be set to either ‘emacs’ or ‘vi’.
- When set to ‘on’, Readline will try to enable the application keypad when it is called. Some systems need this to enable the arrow keys. The default is ‘off’.
- If set to ‘on’, tilde expansion is performed when Readline attempts word completion. The default is ‘off’.
If set to ‘on’, the history code attempts to place point at the
same location on each history line retrieved with
next-history. The default is ‘off’.
- This variable can be set to either ‘on’ or ‘off’. Setting it to ‘on’ means that the text of the lines being edited will scroll horizontally on a single screen line when they are longer than the width of the screen, instead of wrapping onto a new screen line. By default, this variable is set to ‘off’.
If set to ‘on’, Readline will enable eight-bit input (it
will not clear the eighth bit in the characters it reads),
regardless of what the terminal claims it can support. The
default value is ‘off’. The name
meta-flagis a synonym for this variable.
- The string of characters that should terminate an incremental search without subsequently executing the character as a command (see section 8.2.5 Searching for Commands in the History). If this variable has not been given a value, the characters ESC and C-J will terminate an incremental search.
Sets Readline's idea of the current keymap for key binding commands.
viis equivalent to
emacsis equivalent to
emacs-standard. The default value is
emacs. The value of the
editing-modevariable also affects the default keymap.
- If set to ‘on’, completed directory names have a slash appended. The default is ‘on’.
- This variable, when set to ‘on’, causes Readline to display an asterisk (‘*’) at the start of history lines which have been modified. This variable is ‘off’ by default.
If set to ‘on’, completed names which are symbolic links
to directories have a slash appended (subject to the value of
mark-directories). The default is ‘off’.
- This variable, when set to ‘on’, causes Readline to match files whose names begin with a ‘.’ (hidden files) when performing filename completion, unless the leading ‘.’ is supplied by the user in the filename to be completed. This variable is ‘on’ by default.
- If set to ‘on’, Readline will display characters with the eighth bit set directly rather than as a meta-prefixed escape sequence. The default is ‘off’.
If set to ‘on’, Readline uses an internal
more-like pager to display a screenful of possible completions at a time. This variable is ‘on’ by default.
- If set to ‘on’, Readline will display completions with matches sorted horizontally in alphabetical order, rather than down the screen. The default is ‘off’.
- This alters the default behavior of the completion functions. If set to ‘on’, words which have more than one possible completion cause the matches to be listed immediately instead of ringing the bell. The default value is ‘off’.
- This alters the default behavior of the completion functions in a fashion similar to show-all-if-ambiguous. If set to ‘on’, words which have more than one possible completion without any possible partial completion (the possible completions don't share a common prefix) cause the matches to be listed immediately instead of ringing the bell. The default value is ‘off’.
- If set to ‘on’, a character denoting a file's type is appended to the filename when listing possible completions. The default is ‘off’.
- Key Bindings
The syntax for controlling key bindings in the init file is
simple. First you need to find the name of the command that you
want to change. The following sections contain tables of the command
name, the default keybinding, if any, and a short description of what
the command does.
Once you know the name of the command, simply place on a line
in the init file the name of the key
you wish to bind the command to, a colon, and then the name of the
There can be no space between the key name and the colon--that will be
interpreted as part of the key name.
The name of the key can be expressed in different ways, depending on
what you find most comfortable.
In addition to command names, readline allows keys to be bound
to a string that is inserted when the key is pressed (a macro).
bind -pcommand displays Readline function names and bindings in a format that can put directly into an initialization file. See section 4.2 Bash Builtin Commands.
- keyname: function-name or macro
keyname is the name of a key spelled out in English. For example:
Control-u: universal-argument Meta-Rubout: backward-kill-word Control-o: "> output"In the above example, C-u is bound to the function
universal-argument, M-DEL is bound to the function
backward-kill-word, and C-o is bound to run the macro expressed on the right hand side (that is, to insert the text ‘> output’ into the line). A number of symbolic character names are recognized while processing this key binding syntax: DEL, ESC, ESCAPE, LFD, NEWLINE, RET, RETURN, RUBOUT, SPACE, SPC, and TAB.
- "keyseq": function-name or macro
keyseq differs from keyname above in that strings
denoting an entire key sequence can be specified, by placing
the key sequence in double quotes. Some GNU Emacs style key
escapes can be used, as in the following example, but the
special character names are not recognized.
"\C-u": universal-argument "\C-x\C-r": re-read-init-file "\e[11~": "Function Key 1"In the above example, C-u is again bound to the function
universal-argument(just as it was in the first example), ‘C-x C-r’ is bound to the function
re-read-init-file, and ‘ESC [ 1 1 ~’ is bound to insert the text ‘Function Key 1’.
- control prefix
- meta prefix
- an escape character
- ", a double quotation mark
- ', a single quote or apostrophe
- alert (bell)
- form feed
- carriage return
- horizontal tab
- vertical tab
- the eight-bit character whose value is the octal value nnn (one to three digits)
- the eight-bit character whose value is the hexadecimal value HH (one or two hex digits)
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