Re: [opkg-devel] [opkg-utils PATCH] opkg-build: add detection if using GNU tar.

[Paul Barker <paul@paulbarker.me.uk>]

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On Mon, Jun 02, 2014 at 11:50:48AM +0100, tom@ewsting.org wrote:
> From: Thomas Ingleby <thomas.c.ingleby@intel.com>
> 
> * Some options of GNU tar do not exist on other implementations
> 
> Signed-off-by: Thomas Ingleby <thomas.c.ingleby@intel.com>
> ---
>  opkg-build | 17 ++++++++++++++---
>  1 file changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/opkg-build b/opkg-build
> index e314712..8abc14d 100755
> --- a/opkg-build
> +++ b/opkg-build
> @@ -159,6 +159,17 @@ ogargs=""
>  outer=ar
>  noclean=0
>  opkext=0
> +
> +tarformat=""
> +#Probably not the best way to detect if running on a system without full GNU tar
> +set +e
> +tar --help | grep "format" &> /dev/null
> +if [ $? -eq 0 ]
> +then
> +    tarformat="--format=gnu"
> +fi
> +set -e
> +

I wouldn't trust that the word 'format' won't occur in some other context within
the help output of tar. I'd search for '--format' instead, both bsdtar and gnu
tar include that in the help output but busybox tar does not. The output of
busybox tar also seems to be printed on stderr, so I'd include '2>&1' before the
pipe.

You also shouldn't need the 'set +e' magic, if you move the command which could
fail into the if statement then an error should not cause the script to abort.
Maybe try something like:
    if tar --help 2>&1 | grep -- --format > /dev/null; then ...

The rest of this looks good to me.

>  usage="Usage: $0 [-c] [-C] [-O] [-o owner] [-g group] <pkg_directory> [<destination_directory>]"
>  while getopts "cCg:ho:vO" opt; do
>      case $opt in
> @@ -233,8 +244,8 @@ tmp_dir=$dest_dir/IPKG_BUILD.$$
>  mkdir $tmp_dir
>  
>  echo $CONTROL > $tmp_dir/tarX
> -( cd $pkg_dir && tar $ogargs -X $tmp_dir/tarX -cz --format=gnu -f $tmp_dir/data.tar.gz . )
> -( cd $pkg_dir/$CONTROL && tar $ogargs -cz --format=gnu -f $tmp_dir/control.tar.gz . )
> +( cd $pkg_dir && tar $ogargs -X $tmp_dir/tarX -cz $tarformat -f $tmp_dir/data.tar.gz . )
> +( cd $pkg_dir/$CONTROL && tar $ogargs -cz $tarformat -f $tmp_dir/control.tar.gz . )
>  rm $tmp_dir/tarX
>  
>  echo "2.0" > $tmp_dir/debian-binary
> @@ -249,7 +260,7 @@ rm -f $pkg_file
>  if [ "$outer" = "ar" ] ; then
>    ( cd $tmp_dir && ar -crf $pkg_file ./debian-binary ./control.tar.gz ./data.tar.gz )
>  else
> -  ( cd $tmp_dir && tar -cz --format=gnu -f $pkg_file ./debian-binary ./control.tar.gz ./data.tar.gz )
> +  ( cd $tmp_dir && tar -cz $tarformat -f $pkg_file ./debian-binary ./control.tar.gz ./data.tar.gz )
>  fi
>  
>  rm $tmp_dir/debian-binary $tmp_dir/data.tar.gz $tmp_dir/control.tar.gz
> -- 
> 1.9.2
> 
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-- 
Paul Barker

Email: paul@paulbarker.me.uk
http://www.paulbarker.me.uk

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