On Tue, 23 May 2006, Marcus Glocker wrote:

> On Tue, May 23, 2006 at 09:07:04PM +0200, Otto Moerbeek wrote:
>
> > Care to explain? For PS1, posix describes:
> >
> > "PS1 Each time an interactive shell is ready to read a command, the value
> > of this variable shall be subjected to parameter expansion and written
> > to standard error."
>
> "2.2.3 Double Quotes
> The backslash shall retain its special meaning as an escape character
> only when followed by one of the following characters when
> considered sepcial:
> $ ` " \ <newline>"
>
> PS1="$x$(print \\r)$x$(tput so)$x\$PWD$x$(tput se)$x> "
>
> In my understanding escaping \$PWD in double quotes should result
> in $PWD because $ got escaped and looses its meaning as a variable
> holder. So I would assume to just set $PWD in double quotes, which
> still works with my diff applied.

But how exactly? The example puts the current wd in the prompt.

Let's use a more simple example with the current ksh:

PS1="\$PWD "

there are two moments variable substitution takes place. The first is
when assigning to PS1. The \ is needed to avoid immediate expansion
of $PWD, since you want to do that each time a new prompt is
displayed, the piece from posix I quoted earlier says that should be
done each time a prompt is displayed.

So after assigning PS1, it holds the string '$PWD ', which will be
expanded each time a prompt is printed and so have the desired effect
of printing the current wd.

With your diff, the expansion will be done only once, on the initial
assignment of PS1. I do not see how you'd get the current working dir
in a prompt with your diff. And what's more, I do not see how the
current behaviour is non-posix, as you claim.

-Otto