How-to: Bash startup files

~/.inputrc

Although the Readline library comes with a set of default keybindings, it is possible to modify these by putting commands into a .inputrc file, typically in the home directory. The name of this file is taken from the value of the shell variable INPUTRC. If that variable is unset, the default is ~/.inputrc If that file does not exist or cannot be read, the ultimate default is /etc/inputrc

The configuration options in .inputrc are particularly useful for customising the way Tab-completion works, e.g. with the ls command

When a program which uses the Readline library starts up, the init file is read, and the key bindings are set. In addition, the C-x C-r command re-reads this init file, thus incorporating any changes that you might have made to it.

The inputrc variable syntax is simple:

set variable value

Where variable is one of the following:

bell-style

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.

bind-tty-special-chars

If set to ‘on’, Readline attempts to bind the control characters treated specially by the kernel’s terminal driver to their Readline equivalents.

comment-begin

The string to insert at the beginning of the line when the insert-comment command is executed. The default value is "#".

completion-ignore-case

If set to ‘on’, Readline performs filename matching and completion in a case-insensitive fashion.
The default value is ‘off’.

completion-prefix-display-length

When set to a value greater than zero, common prefixes longer than this value are replaced with an ellipsis when displaying possible completions.
e.g. set completion-prefix-display-length 4

completion-query-items

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 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 100.

convert-meta

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’.

disable-completion

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-mode

The editing-mode variable 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’.

echo-control-characters

When set to ‘on’, on operating systems that indicate they support it, readline echoes a character corresponding to a signal generated from the keyboard. The default is ‘on’.

enable-keypad

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’.

enable-meta-key

When set to ‘on’, Readline will try to enable any meta modifier key the terminal claims to support when it is called. On many terminals, the meta key is used to send eight-bit characters. The default is ‘on’.

expand-tilde

If set to ‘on’, tilde expansion is performed when Readline attempts word completion. The default is ‘off’.

history-preserve-point

If set to ‘on’, the history code attempts to place the point (the current cursor position) at the same location on each history line retrieved with previous-history or next-history. The default is ‘off’.

history-size

Set the maximum number of history entries saved in the history list. If set to zero, the number of entries in the history list is not limited.

horizontal-scroll-mode

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’.

input-meta

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-flag is a synonym for this variable.

isearch-terminators

The string of characters that should terminate an incremental search without subsequently executing the character as a command. If this variable has not been given a value, the characters <ESC> and C-J will terminate an incremental search.

keymap

Sets Readline’s idea of the current keymap for key binding commands. Acceptable keymap names are emacs, emacs-standard, emacs-meta, emacs-ctlx, vi, vi-move, vi-command, and vi-insert. vi is equivalent to vi-command; emacs is equivalent to emacs-standard. The default value is emacs. The value of the editing-mode variable also affects the default keymap.

mark-directories

If set to ‘on’, completed directory names have a slash appended. The default is ‘on’.

mark-modified-lines

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.

mark-symlinked-directories

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’.

match-hidden-files

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.

output-meta

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’.

page-completions

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.

print-completions-horizontally

If set to ‘on’, Readline will display completions with matches sorted horizontally in alphabetical order, rather than down the screen. The default is ‘off’.

revert-all-at-newline

If set to ‘on’, Readline will undo all changes to history lines before returning when accept-line is executed. By default, history lines can be modified and retain individual undo lists across calls to readline. The default is ‘off’.

show-all-if-ambiguous

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’.

show-all-if-unmodified

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’.

skip-completed-text

If set to ‘on’, this alters the default completion behavior when inserting a single match into the line. It’s only active when performing completion in the middle of a word. If enabled, readline does not insert characters from the completion that match characters after point in the word being completed, so portions of the word following the cursor are not duplicated. For instance, if this is enabled, attempting completion when the cursor is after the ‘e’ in ‘Makefile’ will result in ‘Makefile’ rather than ‘Makefilefile’, assuming there is a single possible completion. The default value is ‘off’.

visible-stats

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

In addition to the set commands above, .inputrc can also be used to control key bindings, using this syntax:

keyname: function-name or macro

The keyname must spelled out in English, Control-u, Control-k etc. 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).

Example key bindings:

Control-u: universal-argument C-u is bound to the function universal-argument

Meta-Rubout: backward-kill-word M-DEL is bound to the function backward-kill-word

Control-o: "> output" C-o is bound to run the macro expressed on the right hand side (that is, to insert the text ‘> output’ into the line)

Control-j: menu-complete C-j is bound to cycle through the available tab completions.

Control-k: menu-complete-backward C-k is bound to cycle backwards through the available tab completions.

"\t": menu-complete Use tab to cycle through all the possible completions.

"\C-p": history-search-backward Map control-p to allow search for completions to the current line from your history. e.g. type “git” and then hit control-p to cycle through all the recent git commands.

"\ep": history-search-backward Map escape-p to allow search for completions to the current line from your history. e.g. type “git” and then hit escape-p to cycle through all the recent git commands.

"\e[A": history-search-backward Map Up arrow to allow search for completions to the current line from your history. e.g. type “git” and then hit UP to cycle through all the recent git commands.

"\e[B": history-search-forward Map Down arrow to allow search for completions to the current line from your history. e.g. type “git” and then hit DOWN to cycle back through all the recent git commands.

"\C-d": kill-whole-line Map control-d to kill the whole line.

Related Linux commands

bind -V - list the current Readline variable names and values.
bind -p - list the current Readline function names and bindings.
.bashrc - Startup files (Startup scripts and Aliases).
Sample inputrc File