Re: BUG? - 4.0.2 - parameter substitution won't double backslashes in values

[Derek Peschel <dpeschel@eskimo.com>]

On Thu, Feb 07, 2002 at 07:20:38PM +0000, Bart Schaefer wrote:
> On Thu, 7 Feb 2002, Derek Peschel wrote:

> > But I would still expect some change (a backspace should change to "\b" when
> > using "print", or "\b" should change to "\\b" when using "print -r").
> 
> Um, no.  With "print" a "\b" changes to backspace; with "print -r", "\b"
> remains "\b".  In either case a literal backspace remains a backspace.
> 
> If you want to convert backspace and other "control characters" to a
> visible representation, you can use the (V) parameter flag:
> 
> zsh% bs=$(print -n '\b')
> zsh% print ${(V)bs}
> ^H
> 
> Note that the conversion from '\b' to backspace was done by print, and the
> conversion from backspace to ^H was done by parameter expansion.  There is
> no built-in mechanism to convert from backspace to '\b'.

Maybe my explanation was too complicated, or probably you missed the
beginning of the thread.

I have a string containing the characters "a", backslash, "b", "c".
When I print it using "print", it appears as "ac" (because the backslash,
"b" gets converted to backspace).  When I print it using "print -r",
it appears as "a\bc".

I want to use parameter substitution to convert the backslash to two
backslashes.  I haven't managed it yet -- that's what I was referring
to when I wrote "but I would still expect some change".

Assuming I did manage it, I would have the five characters "a", backslash,
backslash, "b", "c".  If I printed _them_ using "print", I would expect
to see "a\bc" and if I printed them using "print -r" I would expect to
see "a\\bc".

My first post has all the examples in it.  Please see that one.

-- Derek