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People are talking about how to prevent the creation of dot underscore files in Mac OSX, but I have never seen them in my Mac.

I am just curious how to create them, any step I can follow?

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AppleDouble files (the ._ files) are created when OS X needs to store a file on a foreign filesystem that doesn't support OS X's rich metadata (things like file flags, resource forks, extended attributes, etc). Since the filesystem doesn't handle the metadata itself, OS X creates 2 files: one with the original file's regular contents (sometimes called its "data fork"), and a second file with a ._ prefix on the filename containing all of the metadata that would otherwise be lost.

Note that even in the situations where OS X creates ._ files, you won't actually see them from OS X -- it'll see that there's a matching pair of files, and display them as a single file with the contents and metadata merged. The only time you'll see them is if you look from some other operating system like Windows (or actually, the Terminal in OS X ).

If you for some reason actually want to create ._ files, just take something like a USB flash drive, format it with the FAT filesystem (OS X's Disk Utility can do this, but it calls the format MS-DOS) (note that most flash drives come preformatted in FAT), and use OS X to copy some files to it. If you want to see the ._ files, plug that drive into a Windows system and take a look.

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