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RE: Ctrl-U doesn't clear read -ep prompt input properly


From: Nellis, Kenneth
Subject: RE: Ctrl-U doesn't clear read -ep prompt input properly
Date: Fri, 7 Aug 2015 19:21:23 +0000

On Friday, August 07, 2015 3:01 PM, Chet Ramey wrote:
> On 8/7/15 9:36 AM, Nellis, Kenneth wrote:
> > Bash Version: 4.3
> > Patch Level: 39
> > Release Status: release
> >
> > Description:
> > Pressing CTRL-U after entering data in response to a read -ep prompt
> should work as does the PS1 bash prompt.
> > Consider a custom PS1 bash prompt containing ansi escape sequences, for
> example, to display
> > the prompt in color. To get proper CTRL-U clearing of input typed at the
> prompt, bash
> > recognizes special \ [ and \ ] delimiters in the prompt string. Here is
> my PS1, for example:
> > \ [ ESC [ 3 2 m \ ] $ SP \ [ ESC ( B ESC [ m \ ] LF
> > which displays a "$ " prompt in green.
> > Without \ [ and \ ] in the prompt, CTRL-U doesn't clear the line
> properly, so it's a necessary feature.
> >
> > read -ep prompt, however, does not support the \ [ and \ ] delimiters.
> Consequently, for prompts containing
> > ansi escape sequences, CTRL-U doesn't clear the line properly.
> >
> > Repeat-By:
> > The following example demonstrates the problem.
> > $ prompt="$(tput setaf 2)test>$(tput sgr0) "
> > $ read -ep "$prompt" answer
> > test> xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx<CTRL-U>
> >
> > Note that all the x's are not cleared.
> 
> You're correct.  The prompt given to read -p prompt is not expanded like
> the PSn variables.  It never has been, and it's not documented to do so.
> As such, using invisible characters in the read -p prompt string is not
> supported.
> 
> Since you're adding the non-visible characters to the prompt, you can
> try bracketing them with \001 and \002, but you have to do that yourself.
> 
> --
> ``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/

Hey, that works! Thanx! Didn't see it in the documentation. My bad?

—Ken



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