Re: [Qemu-devel] [PATCH 1/7] iotests: Allow out-of-tree run

[Max Reitz]

On 16.05.2014 17:09, Eric Blake wrote:
> On 05/16/2014 08:43 AM, Max Reitz wrote:
>
> > > > +    source_iotests="$(cd "$(dirname "$(readlink "$0")")"; pwd)"
> > > This is potentially dangerous. If readlink or dirname fails, you can
> > > invoke cd "" (which on bash is stupidly a no-op instead of an error),
> > > and end up calling pwd in the wrong directory.  But in the common case
> > > it works, so I'm not sure it's worth bending over backwards to make it
> > > more robust.
> > I guess using something like
> >
> > source_iotests="$(dirname "$(readlink "$0")")"; if [ -z "$source_iotests" ]; 
> > then; /* abort */; fi;
> > source_iotests="$(cd "$dirname"; pwd)"
> >
> > should work better, then?
> Or even safer with
>
> source_iotests=$(cd "$dirname" && pwd) || /* abort */
>
> in the second step, to ensure both the cd and pwd commands succeeded.
> (By the way, assignment context does not require "" when passing a
> single shell word, such as command substitution, so foo=$(...) and
> foo="$(...)" are identical)

The more you know... (and of course I meant "$source_iotests" in the 
second step)

> > > Is [ ! '(' -o ')' ] true or false? Depends on whether it was parsed as {
> > > ! '(' } -o ')' (false -o true => true) or as ! { '(' -o ')' } (! (true
> > > -o true) => false)
> > >
> > > But this is bash, so you could do:
> > >
> > > if [[ $arch && -x $build_root/$arch-softmmu/qemu-system-$arch ]]
> > >
> > > for less typing, and no risk of [] ambiguity.
> > If you're telling me I'm free to use bashisms, I'll believe you. :-)
> Well, the script IS being run by /bin/bash, and you already ARE using
> bashisms elsewhere.

I feared so. *g*

Max