export hobba=ksjdjf123ksks
export nokka=`sed “s/[^0-9]//g” <<< $hobba`
echo $nokka
123
Sources: http://stackoverflow.com/questions/13055889/sed-with-a-literal-string-not-input-file, http://stackoverflow.com/questions/6388046/extract-integer-from-string-using-bash
Just Some Techie Notes! 