If you have a file that has been opened by a process, you can unlink the file, either from within the process or, as in your case, by some external agency, but the data will still exist on disk and be available to read until the filehandle is closed or the process exits. However,if you do an ls while the process is still running you will not see the file.

Some "clever" programmers do this to create a working file for their application that nobody else can see; that's all very well until their application throws a wobbly and your disk fills up. As a sys. admin. I've been bitten by this a few times over the years. Your disk is full but you can do du commands until you are blue in the face but you can't see what file is causing the problem. If you can work out which application is causing the problem, killing it will close the filehandle and thereby free the disk space.

If your program is still running with the open filehandle, let it run. The data is still there on disk to be read.

Best of luck,

JohnGG