"._DS_Store" files and the like

tech4all

macrumors 68040
Original poster
Jun 13, 2004
3,400
489
NorCal
I know this has been discussed before but I did a search for "._DS_Store" and found nothing.

Anyways, I had some files (PDFs) on my Mac and then copied them over to a Windows PC via my network. I was going (and did) copy the files from the PC to their destination. Then I get this notice saying that there are 9 hidden files. I went to Tools> Folder Options > View > and chose to show hidden files. Anyways, there are 9 hidden files:

2 of the "._DS_Store" files and 7 other files that correspond to the original file names, only they have a "._" before the file name.

I've seen this stuff before, but forgot the purpose of these files. Any info about these files would be great! :)
 

Mechcozmo

macrumors 603
Jul 17, 2004
5,215
2
.DS_Store files are display information.

Like what icon size you want stuff to be at, where icons are, etc.
 
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rainman::|:|

macrumors 603
Feb 2, 2002
5,438
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iowa
Yep, in OS 9 that information was added to the file as the Resource Fork, leaving the file itself as the Data Fork. Caused a lot of issues with cross-platform compatability, since PCs can't read the resource fork. So now it's stored as a separate file, invisible, so the file itself isn't modified. Makes a lot more sense, you just have to ignore the hidden files sometimes.

edit: no, if you lose them you might lose some customizations (like, where the icon was in the window, or a custom icon or something) but the original file should remain intact.
 
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tech4all

macrumors 68040
Original poster
Jun 13, 2004
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NorCal
So on OS X the files automatically get moved when the original files are moved. Are the files, when in OS X, separate as well (like in Windows), or somehow embedded into the original file?

And on my PC, I copied an original file (not the "._" one) outside of the folder where the "._" file was, and the PDF opened fine. So I'm guessing these "._" files are needed for some customization like paulwhannel said, but the file will open and can be used as normal if the "._" file is not with it....although I never really saw any differences when the "._" was not in the same folder as the original folder.
 
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Mechcozmo

macrumors 603
Jul 17, 2004
5,215
2
tech4all said:
So on OS X the files automatically get moved when the original files are moved. Are the files, when in OS X, separate as well (like in Windows), or somehow embedded into the original file?
They are one file, in a way, but two parts of it. One "fork" of this file contains your data. The words you typed into a report. The other "fork" of the file contains your custom icon, etc. So they are not embedded into each other but rather are one and the same. They are "forks"! :)


tech4all said:
And on my PC, I copied an original file (not the "._" one) outside of the folder where the "._" file was, and the PDF opened fine. So I'm guessing these "._" files are needed for some customization like paulwhannel said, but the file will open and can be used as normal if the "._" file is not with it....although I never really saw any differences when the "._" was not in the same folder as the original folder.
Your PC couldn't give a crap about the "._" or resource fork. It can't use it. Some applications rely on the data in the resource fork to open the data fork... Only by trial and error do you find those files.

tech4all said:
Are they needed to open a file or anything important like that?
Yeah. The data fork!

Remember, you aren't dealing with separate files but rather "forks" of a file. Windows and Linux have no clue what the heck your talking about, and they can only read out of there two files. Macs see it as two forks which comprise one file.
 
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