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Re: [Bug-readline] Fwd: Re: Feature proposal/request: input line highlig


From: Chet Ramey
Subject: Re: [Bug-readline] Fwd: Re: Feature proposal/request: input line highlighting
Date: Fri, 21 Aug 2015 13:46:29 -0400

> >> On 11 Jun 2015 18:10, Thomas Wolff wrote:
> >> > as opposed to having a fancy colored prompt, I would like to be 
> >> able to
> >> > set up coloring of the whole bash command input line (but not the
> >> > following command output). This could be achieved by adding a variable
> >> > like "AFTERPROMPT_COMMAND" which is executed after a prompt line is
> >> > completed (or "PS9" which is output after a prompt line is completed).
> >> > It could even be a nice idea to configure this behavior separately for
> >> > bash and readline, so the users have a choice whether to color just
> >> > command input, readline-handled program input, or both.
> >> > I would appreciate this feature, and maybe even supply a patch if I 
> >> had
> >> > a clue where to hook it in...
> >>
> >> this is already doable -- leave the end of PS1 enabling color.
> >> PS1='\[\e[0;33m\]$ \[\e[34;1m\]'
> >>
> >> this will color the input buffer blue

> thanks for your response, but that's not what I meant because the output 
> of the invoked programs will stay blue. I'll illustrate my idea with the 
> attached screenshot, showing a few possible options.

So the problem is reduced to restoring the normal color before any invoked
program has a chance to produce output.

There are a couple of ways to do it using bash-specific functionality.
Using only readline is hard because readline doesn't really have anything
that just prints text to the terminal -- it's designed to manage an input
buffer.

This bash-specific one is easiest to describe.

1.  Append the character sequence that changes the terminal to the desired
    color to PS1, making sure to bracket it correctly:

        PS1='address@hidden \[\e1;34m\]'

2.  Define a DEBUG trap that will restore the default terminal color settings
    before invoking a command:

        trap -- 'printf "\e[0m"' DEBUG

There are ways to make this work using `bind -x' and readline's key binding
to macros, but that is much more complicated.

Chet

-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU    address@hidden    http://cnswww.cns.cwru.edu/~chet/



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