Re: shouldn't prompt printing be smarter?

[Francesco Montorsi]

Hi,

Bob Proulx ha scritto:
> > PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ 
> > '
> > what is it btw?
>
> That is a pretty standard Debian setting that looks to see if you are
> running inside of a chroot.  Normally inside of a chroot on Debian
> systems the file /etc/debian_chroot has been set (I wish it were a
> more generic name) to the name of the chroot.  That is used to set the
> debian_chroot variable.  The variable setting is used in the prompt
> itself.  You have the color prompt setting uncommented which is pretty
> gnarly.  The non-color one is easier to understand.
>
>   PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w\$ '
>
> It simply places the value of the variable if it is set in the prompt
> inside parenthesis.  If it is not set then it reduces simply to the
> basic '\u@\h:\w\$ '.
thanks for the explanation!


> There are two separate issues.
right

>  One is that you think that the shell
> should be able to dynamically determine the cursor location and add a
> newline if it is not already in the first column.  I disagree.  The
> shell should not do that. 
why?
why would you ever want to have the prompt printed at non-zero column of 
the terminal?

> If you want the shell to always add an
> extra newline then you can always add one to your PS1 setting.  Some
> people do that and like that configuration.
unfortunately in that way I suppose the terminal would then show:

frm@ubuntu:~$ echo hello world
hello world

frm@ubuntu:~$ bash --version
GNU bash, version 3.1.17(1)-release (i486-pc-linux-gnu)
Copyright (C) 2005 Free Software Foundation, Inc.

frm@ubuntu:~$ cd ..

and so on. I.e. an empty line would _always_ be added :(

I think that printing the prompt where the user _always_ expect to have 
it is very important. Current behaviour could be considered a UI bug.
Or otherwise it could be considered a "bug" those programs which don't 
print the final newline.
In any case I really think that having the prompt printed in the _wrong_ 
place (i.e. in the wrong place from the user's POV) is indeed a 
usability bug.

To make everyone happy an option could be added to define the wanted 
behaviour.


> Second is that you think there should only be one prompt printed in
> that case.  I agree. 
me too

> But I cannot recreate your behavior here and I
> cannot think of how that would come about.  I am afraid you will have
> to try to debug it further on your end. 
I think I've restricted the possible sources of the problem. I've 
grabbed bash 3.2 tarball and compiled it. The problem does not appear 
there. It only appears with:

GNU bash, version 3.1.17(1)-release (i486-pc-linux-gnu)
Copyright (C) 2005 Free Software Foundation, Inc.

I've also found that Ubuntu guys made some diff to vanilla bash 3.1:
http://archive.ubuntu.com/ubuntu/pool/main/b/bash/bash_3.1-5ubuntu3.diff.gz

I've scanned it but couldn't see anything related, though...

Should I submit a bug to Ubuntu package or someone on the list has bash 
3.1 and can look if is able to reproduce the problem?

I may also decide to upgrade my distro to the new beta Ubuntu Feisty 
(which has bash 3.2 to see if the bug was fixed there...)

Thanks,
Francesco