Bash Readline – Using Bind to Read the Current Command Line

bashreadline

I'm using bind -x to execute a script whenever a certain key sequence is pressed.

For example I have a script at /usr/local/bin/foo with the contents

#!/bin/bash
echo foo

If I run bind -x '" ": /usr/local/bin/foo' then every time I press the space bar twice it echos "foo". So far so good.

What I want to be able to do is access (and ideally modify) the current command that's being entered. If I type some really long command (there are two spaces at the end) my script gets executed but how can it see that I've already entered some really long command and change it to some other long command?

Best Answer

Based on this answer, I think you would have to make your script into a sourced bash function, have it modify READLINE_LINE (and READLINE_POINT according to the new length / desired cursor point), and then bind -x '" " : that-function-name'.

Just to clarify; if you only want to modify some commands with double-space, do something like:

autocomplete() {
if [ "$READLINE_LINE" = "some really long command" ]
then
    READLINE_LINE="some other long command"
    READLINE_POINT=23
fi
}

bind -x '"  " : autocomplete'

Related Solutions

Bash – Delete whole argument in current bash command-line

Bash has readline commands that aren't bound by default. You can find them at reference: http://www.gnu.org/software/bash/manual/html_node/Bindable-Readline-Commands.html#Bindable-Readline-Commands

The command you are looking for is called shell-backward-kill-word. You have to select a shortcut first. Let's use Ctrlp, since it's "previous command" - same as up arrow.

bind '"\C-p": shell-backward-kill-word'

Bash – Modify $READLINE_LINE and $READLINE_POINT values inside bash script

Just by the same reason why this won’t work:

$ export a=1
$ bash -c 'echo $a; let a++'
1
$ echo $a
1

Environment variables are heritable, not shareable. Since autocomplete.sh is executed as a new child process, it can read all parent’s variables, but can‘t push new values back.

To modify READLINE_LINE and READLINE_POINT you have to execute your autocomplete in the same process – source and functions will help you.

# autocomplete.sh
# should be sourced from ~/.bashrc or something

autocomplete() {
    echo $READLINE_LINE $READLINE_POINT
    EXPANSION=($(magical_autocomplete $READLINE_LINE))
    #we store the desired value for the line in ${EXPANSION[0]}
    [[ ${#EXPANSION[@]} -gt 1 ]] && echo ${EXPANSION[@]:1}

    READLINE_LINE=${EXPANSION[0]}
    READLINE_POINT=${#READLINE_LINE}
}

Binding:

if [[ -s "$HOME/.bashrc.d/autocomplete.sh" ]]; then
    source "$HOME/.bashrc.d/autocomplete.sh" 
    bind -x '"\t" : autocomplete'
fi

Best Answer

Related Solutions

Bash – Delete whole argument in current bash command-line

Bash – Modify $READLINE_LINE and $READLINE_POINT values inside bash script

Related Question