Mike Frysinger <vapier <at> gentoo.org> writes:
> > cd /tmp
> > mkdir -p sub
> > {
> > ln --at=4 -sf foo bar # call symlinkat("foo",4,"bar")
> > readlink --at=4 -m bar # call areadlinkat(4,"bar")
> > } 4< sub
> >
> > would output /tmp/sub/foo.
>
> isnt this possible today under linux by using /proc/self/fd ? i'm not
> suggesting this as a clean/portable replacement, just trying to better
> understand the proposal.
Yes, with sufficient /proc supprt, the above example would be equivalent to:
cd /tmp
mkdir -p sub
{
ln -sf foo /proc/self/4/bar
readlink -m /proc/self/4/bar
} 4< sub
Without /proc, it's similar to doing everything via absolute or anchored paths
(or using shell variables for shorthand), but then you lose time with O(n^2) on
deep nesting of directories, as well as the robustness that the *at functions
give in the case that some other process is modifying the same hierarchy that
you are operating on:
cd /tmp
mkdir -p sub
dir=sub
{
ln -sf foo "$dir"/bar
readlink -m "$dir"/bar
} 4< "$dir"
> --at-fd might be a better explicit option without getting too verbose ?
Indeed.
--
Eric Blake
