问题
I am writing my own tar archiver. All works fine inside my app (even reading tars generated with other tools) however I cannot get my tar files to work with 3rd party tar file readers. So I tried building a tar file on the command line, building one with my code and binary comparing the two.
But there seems to be an issue:
I have a textfile called Test.txt which I want to add to my tar, so I run the following command in the terminal:
tar -c -f x.tar Test.txt
When doing this:
tar -tf x.tar
I get the following list:
./._Test.txt
Test.txt
This is in the Terminal on Mac OS X Lion.
Where does that ./._Test.txt file come from? I don't see it when doing an ls -a
Upon inspecting the tar contents it seems to be some binary data, but I have no idea where it comes from.
回答1:
It's a representation of the file's resource fork/extended attributes.
Try ls -l@ Test.txt and xattr -l Test.txt to see what extra stuff OSX tacked on to the file.
回答2:
You can add the following to your bashrc file -
export COPYFILE_DISABLE=true
Or, you can add this option to your tar command at the extraction time
tar -xzpvf x.tar --exclude="._*"
回答3:
As of bsdtar 3.0.3 - libarchive 3.0.3 (and perhaps earlier) there's a new (Mac OS X specific) option to the bsdtar command called --disable-copyfile to suppress the creation of ._ files.
回答4:
This is the way OSX stores the file system forks when the target file system does not support them.
See: http://en.wikipedia.org/wiki/Fork_(file_system)
来源：https://stackoverflow.com/questions/8766730/tar-command-in-mac-os-x-adding-hidden-files-why