check_list_include_item.sh

function list_include_item {
  local list="$1"
  local item="$2"
  if [[ $list =~ (^|[[:space:]])"$item"($|[[:space:]]) ]] ; then
    # yes, list include item
    result=0
  else
    result=1
  fi
  return $result
}

`list_include_item "10 11 12" "11"`  && echo "yes" || echo "no"