I'd just like to know why if I "tar -czf" a file/directory, osx adds a: ._ for each file? I see these when I untar in linux. Or when I work with the uncompressed project in eclipse as it doesn't like them at all. I use 10.7.5.
OS X's tar uses the AppleDouble format to store extended attributes and ACLs. tar and Archive Utility also know how to convert the ._ files back to the native formats, but the ._ files are kept if the archive is extracted on another platform or on a non-HFS volume.
You can usually just tell tar to remove the metadata by setting COPYFILE_DISABLE to some value:
Information stored as extended attributes:
You can see ACLs with
Those files were always there, but they are invisible in Finder (and most Mac OS applications). See http://superuser.com/questions/212896/
That is: these files contain the extended file attributes ... en.wikipedia.org/wiki/Extended_file_attributes ... and they were created as soon as MacOS gave extended attributes to the files. So these ._* files were not created for the tar archive.