echo $x | sed "s/^[^0-9]*\([0-9]*[.]*[0-9]*\)[^0-9A-Z]*GB.*/\1/g"

##</code><code>##

echo $x | sed "s/.\+ \([0-9]\+\)GB.*/\1/g"

##</code><code>##

echo $x | perl -ple 's/.+?(\d+)\s?GB.*/$1/'