Deleting files on external storage, not actually deleted

[elf69]

OK so this might be normal Mac way of doing things.

I had mp3 files on SD card and deleted them on my iMac.
put card back in car radio and it played songs I had deleted.

So I decided to tinker with a USB HDD.
deleted an 8GB folder (after backing up elsewhere) but the extra space did not show up in "get info" of the drive.

However I emptied the bin and then the extra space showed up.

When I removed files from SD card I did not empty the bin.
Is this why the radio in car can still play the removed files?
Until empty bin they still there?

This might be normal, I came from windows background and this is first time it has come to light as started using SD in radio, was using bluetooth from phone before.

 

[Fishrrman]

The files aren't "gone" until you empty the trash...

 

[hobowankenobi]

Yep, mostly normal.

If you think about it, it makes sense. Putting files in the trash just sets a flag, not unlike moving from one folder to another on the same volume. The files don't actually move on the hard drive.

This is always the case. And, bonus: when you empty the trash, they are still not really removed. Another flag is set that marks the space on the drive as available, the amount of free space goes up, so the files are effectively invisible to the OS and user, and new data can be written there...but they are not actually gone until new data is written over them (or a secure delete is performed).

The odd thing here is that once in the trash, they should not show up to the OS/user (except in the trash). I am assuming the flag set by MacOS is not fully recognized by the limited stereo OS....so the devices still sees the (trashed) files, and they still play.

---

One exception to this is a file server (all platforms). If you have a mounted share and you delete files on it (files are on the server), you will get a warning that the files will be deleted immediately (NOT go into the trash).

This makes sense too: If you drag the files to the trash/recycle bin, they would have to be copied—over the network—to your computer trash can. Then you would have to empty it. If we are talking lots of big files, this could take ages. If they went in the server trash....who should be able to see them? How many users can access the trash, empty the trash, move stuff out of the trash, etc.

Point is...the trash/recycle bin is a bit more complicated than most folks consider.

 

[elf69]

thanks guys. so need put SD back in mac and empty bin.

Windows don't do this.

The files are not visible in the mac on SD card but the radio still see them.
That's the bit that I found odd.

 

[Bruno09]

The files are not visible in the mac on SD card

The files are visible in the trash when the SD card is connected to the Mac.

The trash in the Finder is actually a folder that contains the items of all trashes (trash of Macintosh HD + trash of the SD card + trash of other volumes attached if any).