Still in Use
Still in Use
[Cueball is trying to take out a trash bag from his garbage can.] Trash: Sorry, you can't empty the garbage yet. A paper towel in here is currently in use by some object in your house.

Cueball is trying to remove the trash bag from his garbage can. However, the can refuses to let him do so, citing that a paper towel in the trash is being used by some object in his home.
This comic draws parallels between the act of emptying a physical rubbish bin and emptying the recycle bin integrated into a desktop computing environment like Windows, macOS, most Linux derivatives, and others. It originated with the Xerox Alto , but was first commercially introduced on Apple Lisa in 1982 called Wastebasket and, while it was adopted by most other desktop environment operating system, using slightly different names, the main purpose still remains: A user can restore a file after they have deleted it -- hence the most common name recycle bin , you still can get your paper towel and use it again. In many (earlier) command line based systems like DOS or UNIX/Linux (besides the desktop interfaces) a removed file was gone. Some undelete commands exist, but there are hard restrictions because the then free space on the hard drive must not have been used again and often file names aren't fully recoverable.
But sometimes when attempting to delete files, a running program may still have the file marked as in use. The operating system will therefore prevent the file's deletion, but some do not tell the user which program is using the file.
Preventing the file from being deleted from the file system in this case may be a correct behavior, because the document is still being worked on. But sometimes it may happen erroneously, perhaps because of a program not closing the file properly, a glitch in the operating system, or user error. The user then is required to find the cause of the problem and rectify it before the file can be deleted. This may be difficult because error messages may not reveal the affected file or the program blocking its removal. Similar problems may occur when unmounting (or "safely removing") a removable storage device.
The title text may refer to a simple solution to these sorts of problems: Wait a while, perhaps overnight, and see if the (unknown) application(s) have closed the open file(s). Alternatively, the user can shut down the system to make absolutely sure that nothing is using anything. This is usually effective and harmless -- programs that falsely flagged something in the recycle bin as "in use" usually won't recreate the problem when the computer finishes booting up -- but this is really not a convenient solution for the user because all applications are closed.
Advanced users may be inconvenienced by unhelpful error messages but at least are likely to know the tools available to solve the problem. However, a less experienced user just trying to free some space is not only annoyed, their only solution is to reboot or shut down the computer.
Some tools:
[Cueball is trying to take out a trash bag from his garbage can.] Trash: Sorry, you can't empty the garbage yet. A paper towel in here is currently in use by some object in your house.
