Re: PROMPT_COMMAND causing strange cursor behavior

[Martin Sebor]

On 04/28/2015 08:26 AM, Chet Ramey wrote:
> On 4/27/15 1:26 PM, Martin Sebor wrote:
>
> > Bash Version: 4.3
> > Patch Level: 33
> > Release Status: release
> >
> > Description:
> > When the PROMPT_COMMAND variable is set to a command such a printf
> > it causes the cursor to jump to disappear or jump to the wrong
> > positions when typing text that spans more than physical terminal
> > line. The problem exists in at least Bash 4.2 and 4.3 (but likely
> > earlier versions as well).
>
> This isn't exactly a bug.  If readline doesn't know where the cursor is
> when it starts to perform redisplay, it's not going to be able to put the
> cursor in the right position.  Readline assumes that cursor starts in
> column 0 and makes redisplay decisions based on that.

Yes, I subsequently found a report of a similar problem here:
http://lists.gnu.org/archive/html/bug-bash/2009-03/msg00004.html

It seems that PROMPT_COMMAND shouldn't (isn't intended to) be
used for commands that produce output. If that's so, may I
suggest to mention it in the manual?

Otherwise, the trouble is that there are tools that use the
variable for just that purpose.

Thanks
Martin