Re: [1003.1(2008)/Issue 7 0000124]: tilde expansion and double slashfile names

[Eric Blake <ebb9@xxxxxxx>]

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According to Geoff Clare on 7/15/2009 8:00 AM:
> Both techniques can be used with ~ just the same as with "$HOME",
> but you have a point that the more modern "${dir%/}" technique
> can be used with "$HOME" but not with ~.

> 
>     case $dir in
>     */) pathname=$dir$filename ;;
>     *) pathname=$dir/$filename ;;
>     esac

In this case, a direct translation to tilde-expansion won't work:

*/) pathname=~$filename ;;

because it forms a tilde-prefix with characters not valid in LOGNAME
(~$filename) and thus gives unspecified behavior.

Using a temporary variable could be an option:

tmp=~root
case $tmp in
*/) pathname=$tmp$filename ;;
*) pathname=~root/$filename ;;
esac

but it would certainly be nicer to guarantee that ~root/$filename always
specified the desired file, without needing an intermediate variable.

> 
> or:
> 
>     pathname=$dir//$filename

This approach works to avoid the implementation-defined nature of //, but
doesn't work if $dir is exactly //.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             ebb9@byu.net
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