字典的键天生是唯一的，所以可以用字典来删除文件的重复行，为了完成这项工作可以采用保存这些行的原始排序的方法。
The keys of a dictionary are inherently unique, so it's possible to use a dictionary to remove duplicate lines from a file, and to do so in a way that preserves the original ordering of those lines.
Linux的优点在于，它保存了文件的名称，甚至可以告诉我们它已经被删除。
Linux was nice in that it saved the name of the file and even told us it was deleted.
在你的home目录下练习使用vi，可以使用 vi文件名创建一个 新文件，添加和删除文本，保存文件以及再次调用vi。
Practice with vi in your home directory by creating a newfile with vi filename andadding and deleting text, saving the file, and calling it up again.
当你删除存储在计算机上的文件时，这些数据并没有真正移除，它们的信息被保存在操作系统可以查询到的目录中。
When it comes to data stored on your computer, deleting files doesn't actually remove the data.
此外，您可以创建和删除文件夹保存一些自定义的规则。
Further you can create some custom rules for keeping and deleting folders.
您可以轻松地选择一个或多个附件并保存到所需的文件夹所有的人，以及你可以删除不必要的耗费太多的邮箱中的磁盘空间大的附件。
You can easily select one or more attachments and save all of them into the desired folder, as well as you can delete unwanted large attachments that take too much disk space in your mailbox.
您可以轻松地选择一个或多个附件并保存到所需的文件夹所有的人，以及你可以删除不必要的耗费太多的邮箱中的磁盘空间大的附件。
You can easily select one or more attachments and save all of them into the desired folder, as well as you can delete unwanted large attachments that take too much disk space in your mailbox.
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