Re: [Qemu-devel] [PATCH v2 1/3] qemu-iotests: Modern shellscripting (use $() instead of ``)

[Eric Blake <eblake@redhat.com>]

On 10/17/18 10:17 PM, Mao Zhongyi wrote:
> Various shell files contain a mix between obsolete ``
> and modern $(); It would be nice to convert to using $()
> everywhere.
> 
> `pwd` and `basename $0` are in 231 files under directory
> tests/qemu-iotests, so replaced it with the following:
> 
> sed -i 's/`pwd`/$(pwd)/g' $(git grep -l "\`pwd\`")

No. Instead, I'd rather a separate patch that does:

s/`pwd`/$PWD/
s/\$(pwd)/$PWD/

since POSIX requires $PWD to be sane, and thus save us a wasted forked 
process.

> sed -i 's/`basename $0`/$(basename $0)/g' $(git grep -l "basename \$0")
> 
> A small amount of the rest is manually modified.
> 
> Cc: kwolf@redhat.com
> Cc: mreitz@redhat.com
> Cc: qemu-block@nongnu.org
> 
> Signed-off-by: Mao Zhongyi <maozhongyi@cmss.chinamobile.com>
> ---

> +++ b/tests/qemu-iotests/001
> @@ -21,10 +21,10 @@
>   # creator
>   owner=hch@lst.de
>   
> -seq=`basename $0`
> +seq=$(basename $0)
>   echo "QA output created by $seq"
>   
> -here=`pwd`
> +here=$(pwd)
>   status=1	# failure is the default!

At one point, someone (Jeff?) proposed a cleanup patch that got rid of a 
lot of cruft in iotests, including the fact that scripts that don't use 
$seq don't need to assign seq=$(basename $0).  We should probably revive 
that rather than just making pointless churn on stuff that is garbage 
anyways.  But I don't have time to look up a URL to that older series at 
the moment.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org