Help on controlling BASH command line

[John Wildberger]

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.
John
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