File names and extensions

I have just started using LibreCaD, SCM Revision: 2.0.9 under ubuntu on a laptop computer.
In “Application Preferences” I have an “Auto save” time of 5 minutes, and “Auto backup” is ticked.

Does “Auto save” over-write the file from which a drawing was opened?
Where is the “Auto backup” file saved, and how often does this take place?

(Incidentally, under “Defaults for new drawing”, the metric unit of length is the metre, not meter !!)

I have one drawing, let’s call it Beacons.dxf

The computer file listing shows two related files: -
Beacons.dxf, Type – Image, Modified – 19May16
Beacons.dxf~, Type – Unknown, Modified – 19May16,   (Note the tilde, “~”  )

What is the second file?

When I open LibreCAD and click the “Open” icon, I find listed: -
#Beacons.dxf, dated 20May16   (Note the “#”, and the date.)
Beacons.dxf, dated 19May16

What is the “#” file all about?  Where has the “#” come from?
Why is the .dxf~ file of 19May16 not listed?

The auto save file is placed in the same folder as the original file. Thus the original file is not touched by the auto save function.
The #Beacons.dxf is the auto save file, LibreCAD adds the # to the file name.

The Beacons.dxf~ is a Ubuntu feature, it is a backup of the original file when it was opened. In case it is needed, it has to be renamed.

#Beacons.dxf is helpful when LibreCAD crashes, then this file may have saved latest changes of your work.
Beacons.dxf~ is helpful when you have accidentally saved your work, then the original file is overwritten, but the dxf~ file contains the content, when the file was opened.
It is not listed in the file open window, as it doesn't match the *.dxf filter.

It is save to delete both files if the original file is okay.

Armin

Many thanks LordOfBikes, all is now sweetness and light.

Both the tilde file and the # autobackup file are brilliant features.

Just a few more suggestions/questions.

1.  Please could this be put in the manual, for other newbies?  Your explanation is far more lucid than mine would be.

2.  Could the Edit/Application Preferences/Defaults Tab/Program Defaults information be modified so that the same expression is used for both the time box and the tick box.  “Auto backup” may be better, because “Auto save” implies that the existing file is over-written, as in a normal “save”.
Putting both boxes on the same line would make things more obvious.  
Adding your explanation to the pop-up explanation for “Auto backup” would also be very helpful to users, although even more helpful – add the text to the page.

3. The time units could be shown with the box title, as in “Auto backup time (Minutes):” , instead of being hidden in the pop-up explanation.

4,  How’s that for inconsistency – the pop-up explanation for “Auto backup” appears when the cursor is hovered over the text, but for the pop-up explanation for “Auto save time” it has to be hovered over the box.

3.  Could the “#” be put AFTER the file name instead of before it?  Putting it before the file name means that the “#” version may be off the bottom of a page in a longer, usually alphabetic, list, instead of the related files being listed consecutively.

4.  Why am I getting some ## (Double hash) files?  Is it simply because I have opened and worked on a # file?

I have used AutoCAD, TurboCAD, and several others for the past thirty years.  I much prefer LibreCAD, for several reasons.  Congratulations to all concerned.