a,b,c,d,e1,2,"3,4,5",6,7 >a.txt
grep [a-z] a.txt|cut -d',' -f3 && grep [0-9] test.txt |cut -d'"' -f2
sed -r 's/([a-z0-9]+,){2}"?([^"]*)"?(,[0-9a-z]){2}$/\2/' a.txt
