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I downloaded a Java library and noticed, that for every file and directory there is a binary file of the form ._<name>. It contains something like:

"Mac OS X ... ..."

Have those files been added by an Mac OS X IDE (I'm an Ubuntu user planning to use the library with Eclipse)? Can I safely remove those files?

TIA for your help!

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up vote 6 down vote accepted

Those are extended attribute files, which OSX uses when the filesystem doesn't support resource forks or extended attributes. You don't care about them. (The entry you quoted is a message to the Finder to display a "This file was downloaded at (date). Downloaded programs may be unsafe. Do you want to open it?" dialog along with a button which will open Chrome and take you to the page the file was downloaded from.)

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While the attributes these files (technically "AppleDouble" files) are generally unnecessary, there are a few cases where they are actually important. Alias files are an example that comes to mind -- without the type code, they won't even be recognized as aliases. – Gordon Davisson Mar 14 '11 at 7:04
But on Ubuntu, they're not going to be recognized anyway. (See the original question.) – geekosaur Mar 14 '11 at 7:11
agreed, as long as the files will be used on the Ubuntu system (where things like aliases wouldn't work anyway). If they were going Mac -> Ubuntu -> Mac, then the AppleDoubles might matter. – Gordon Davisson Mar 14 '11 at 7:38

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