Re: [Help-bash] `read -e -p`, colors, and invisible chars

[Dennis Williamson]

On Aug 26, 2015 8:06 PM, "Mike Frysinger" <address@hidden> wrote:
>
> my desire is simple:
>   show a custom colorized prompt when reading input and leverage readline
>   (for editing & history)
>
> the `read` builtin almost gets me there:
>  - the -p flag allows you to specify a custom prompt
>  - the -e flag uses readline for input
>
> however, the -p flag does not parse escape sequences.  np, just expand
> that myself ahead of time using `printf %b`.  simple example:
>   prompt=$(printf '%bfoo>%b ' '\033[1;33m' '\033[0m')
>   read -e -p "${prompt}"
>
> now i hit the classic invisible char problem when readline tries to
> redraw the prompt (just hold up on the arrow key to draw many lines
> from your history).  normally i'd leverage \[ and \], but bash does
> not seem to support that w/the read builtin -- they get rendered in
> the output directly instead of being consumed.
>   $ prompt=$(printf '%bfoo>%b ' '\[\033[1;33m\]' '\[\033[0m\]')
>   $ read -e -p "${prompt}"
>   \[\]foo>\[\]
> (yes, moving the \[ and \] to the printf string yields same behavior)
>
> am i out of luck ?  if so, can we change the behavior of -p to support
> escape sequences naturally ?  maybe have it go through the same prompt
> code paths as the bash loop ?  e.g. this would "just work":
>   read -e -p "$PS1"
>
> if we're worried about breaking existing -p users (who might have an
> escape sequence in there and actually want it), maybe we can add a
> new -P flag ?  although i'd say too bad and just put it behind the
> existing bash version compat shopt settings ...
> -mike

Use \001 and \002 instead of \[ and \].