How to delete trash from command line

When you delete files or folder on lubuntu normally it will goes to trash can first, and then you can permanently delete if you wish, but sometimes it doesn't work, there are some files that can't be removed on the trash can. The solution is to delete from command line.

How to show directory only with ls command

The ls command on lubuntu (and linux in general) will output list of files and directory, but what if i just need to show list of directory with ls? how to show directory only with ls command?