I copied a number of mp3 files from my Mac running the Big Sur OS to a USB flash drive and then copied them to my Windows 10 pc. There are files on my PC that are not on my Mac. They are named ._.<filename>.mp3. What are these files used for on the Mac and can they be deleted from my Windows 10 PC. Thanks.
Mac mini, macOS 11.2
On a Mac, file names that begin with a period are “hidden,” so you don’t normally see them in the Finder. They are used by the operating system to keep track of things like where the icons show up in the Finder window, as I understand it. Windows doesn’t need/use them as far as I know.
Before you eject that USB stick from the Mac, open the Terminal application and run the following on your mounted USB stick name:
dot_clean -m /Volumes/USBStickName
That will do exactly what the name says and after you run this command, the dot underscore filenames will be gone from the USB stick. Then eject it.
mcintoshbear1 wrote:
I will try this tomorrow when I have an appropriate amount of time.
Your reply is helpful ... but being a former database administrator in another life it does not answer my question of what is the function of the file in Big Sur? I like to understand why I am doing things, when I do understand I am more likely to remember to run the application that fixes the issue.
It is the MetaData for the file of the same name. You are moving the file to a file system that cannot store the metadata in the same file as the data file. It splits the metadata out of the resource fork and stores it in at the dot underbar file.
You could always "man dot_clean" to find out a little more about the program.
I have used dot-clean in an Automator applet so I don't have to launch Terminal to run it. I use it whenever I copy files to a FAT/exFAT flash drive for the smart TV or to Windows at work.
I made it the following way. The only drawbacks are that the flash drive must be named "UNTITLED" and that it does not automatically eject (in Mojave I had a similar applet that had a prompt for a disk name and ejected it when done but that no longer works in Big Sur). Maybe I should add -m switch to the command?
Applications > Automator > New Document > Application > drag "Run Shell Script" to the area on the right > type without quotes "dot_clean /Volumes/UNTITLED" to the text area > File > Save... > save with a name like "dot_clean UNTITLED" to /Applications.
There's also a shareware that does an excellent job of managing these:
I will try this tomorrow when I have an appropriate amount of time.
Your reply is helpful ... but being a former database administrator in another life it does not answer my question of what is the function of the file in Big Sur? I like to understand why I am doing things, when I do understand I am more likely to remember to run the application that fixes the issue.
What is the file size?
Does anything happen when you try to play the music in them?
The ._.<filename>.mp3 files are all 4.00 KB (4.096 bytes)
The MP3 files are 108 MB (113,281,583 bytes) They have about 2 hours of audio/music.
Drag the MPs files to copy.
When I open the MP3 files in a media player they play as intended.
That is what I did when I copied them from the Mac to the USB flash drive.
Thank you for your responses. I enjoyed the learning experience. All in all, I probably learned more from posting my question here rather than speaking with Apple Support.
what are ._.<filename>.mp3 files?
