Help on controlling BASH command line

[Lennart Sorensen]

On Mon, Jun 06, 2005 at 03:27:12PM -0400, John Wildberger wrote:
> On Monday 06 June 2005 01:44 pm, Lennart Sorensen wrote:
> 
> > The new line is a feature of bash that it knows about, so it starts
> > counting fresh.  If it works without that newline in the prompt, then I
> > will be impressed, since I don't think bash knows about escape codes
> > (being escape stuff, not just bash \ codes).  Your test doesn't seem to
> > show anything.  Of course setting PS1= works since bash sees plain ascii
> > charaters being typed as a command and of course that wraps fine.  It is
> > when it tries to display the prompt and figure out how long it is that
> > things break, which your newline at the end of the prompt conviniently
> > avoids by starting a new prompt line with no escape codes to confuse
> > bash.
> >
> > I personally can't imagine wanting to have a two line prompt.  Seems
> > inefficient.
> 
> 
> 1  [john]:  02:57 PM   [~] $ PS1="\u [\w]\$ "
> 2  john [~]$
> 3  john [~]$ PS1="\n\e[43;1m[\u]:\e[m \e[42;1m \@ \e[m \e[44;1m [\w] 
> 4  \e[m\n\\$"
> 5
> 6  [john]:  02:59 PM   [~]
> 7  $PS1="\e[43;1m[\u]:\e[m \e[42;1m \@ \e[m \e[44;1m [\w] \e[m\\$"
> 8  [john]:  03:00 PM   [~] $
> 9  [john]:  03:00 PM   [~] $ PS1="\e[43;1m[\u]:\e[m \e[42;1m \@ \e[m \e[44;1m 
> 10 [\w] \e[m\n\\$"
> 11 [john]:  03:08 PM   [~]
> 12 $
>  
> Line 1: PS1 changed to simple prompt
> Line 3: Changed to complex prompt with \n at both ends
> Line 7: similar to line 3,but without the two newlines.
> Line 8: new prompt.
> Line 9: similar to line 3, but with \n at the end  only
> Line 12 Entry point for new commands.
> 
> As  an aside, I usually add my newly modified prompt to /etc/bashrc. This way 
> the modification will be seen by all users and by root. I also don't bother 
> of showing the \h option, which would just show 'localhost' in my usage. It 
> might be useful for more sophisticated users though!
> 
> Why you want to use prompt extending over several lines:
> When compiling from source there is a stage when you have to 
> execute ./configure. This might require sometimes a long string of options 
> that can easily extend over several lines. Examples can be found in LFS 
> (Linux From Scratch). With my modified prompt I had never any problems, even 
> with as many as 4 lines of commands and options strung together.

Which version of bash are you using?

It does not do proper wrapping here using bash 2.05.0(1)-release using
your prompt above.

When I switch to bash3 then it does work.  bash2 is often the default
due to bugs/incompatible changes in bash3.

You may be using bash 3.x which likely fixed that problem in a similar
way to how zsh has fixed it years ago.

Lennart Sorensen
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