Re: Colorized Prompts Problem - Thanks for the Deconstruction
On Mon, May 04, 2015 at 12:31:15PM -0500, David Wright wrote:
> Quoting Thomas H. George (lists@tomgeorge.info):
> > On Mon, May 04, 2015 at 06:54:40AM +0000, Bonno Bloksma wrote:
> > > Hi,
> > >
> > > > I entered the following in .bashrc
> > > >
> > > > PS1='\033[01;33m\h:\w\$ \033[00m'
> > > >
> > > > to colorize the prompt (very handy to find the prompt when a command
> > > > fills the console screen with lines of text)
> > > >
> > > > The only problem occurs when the next entry is more than one line. In that
> > > > case the entry wraps around without moving to a new line.
> > >
> > > I had the same problem using the prompt I found at first, I think it is the same you are using. It seems there is a problem in closing the ANSI code string.
> > > Someone else gave me this:
> > > PS1='\[\e[0;31m\]${debian_chroot:+($debian_chroot)}\h:\w\$\[\e[m\] '
> > > This does not have the problem, I have been using this now for over a year, no problems at all.
> > >
> > > Bonno Bloksma
> > >
> > Thank you, this works while nothing else did. The sequences to start
> > and end coloring are different and the colors are different too.
>
> Perhaps it's worth deconstructing this into its constituents:
>
> '\[\e[0;31m\]${debian_chroot:+($debian_chroot)}\h:\w\$\[\e[m\] '
>
> Take out ${debian_chroot:+($debian_chroot)}
> As explained before, this prints the value of $debian_chroot but uses
> the :+ trick to avoid printing () when $debian_chroot is empty/unset.
>
> '\[\e[0;31m\]\h:\w\$\[\e[m\] '
>
> Take out the two \[ and \] brackets.
> As explained before, these brackets must enclose anything that doesn't
> advance the cursor, ie the colouring strings. That tells bash to
> ignore those strings in calculating how much room the prompt has taken
> up. That's the fix for your original complaint.
>
> '\e[0;31m\h:\w\$\e[m '
>
> Take out \h:\w\$ and that space at the end.
> That's the prompt that you want to see coloured. (In your original,
> the space at the end of the prompt was coloured too.)
>
> '\e[0;31m' and '\e[m'
>
> Now all that remains is colour-on and colour-off.
>
> Off: Where you had \033[00m this has \e[m because the 00 before the
> m is unnecessary (blank is zero), and \e is a clearer way of writing
> the ESCape character (octal 33) in more modern versions of bash.
> (The latter eliminates one source of confusion: the mixture of octal
> and decimal numbers.)
>
> On: Similarly, where you had \033[01;33m this has \e[0;31m which,
> as pointed out below, changes the foreground colour to normal red.
> So you should set it back to \e[1;33m
>
> It is harmless, but that leading 0 that you had in 01;33m could be a
> cause for confusion; the numbers before the m are *decimal* whereas
> \033 is octal. So 33m actually means 30 + 3 m where 30 is the
> foreground colour, 3 is the yellow, and m is colouring rather than,
> say, moving the cursor.
>
> Cheers,
> David.
>
Your explanation is very helpful, converts the jumble I copied from a
website into a logical sequence of instructions. I really appreciate
being able to understand the meaning of the prompt.
Tom
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