4913

The world is more mysterious than I realised.

Before reading on, do you know the mysterious property of 4913?

As regulars here know, I am a Linux user. My favourite editor is one found on every unix machine, namely vi. Well, not the actual original vi, whose movement commands are somewhat cryptic, but the replacement vim (“vi improved”), which does at least use the arrow keys in the way you would expect. (Did I ever tell the story of how I persuaded John Conway to produce a paper for a conference proceedings published in time for the conference?)

I usually use vi from the command line in a terminal. But, possibly because of advancing age causing advancing holes in my memory, I have once or twice recently used the file selector to find the file I am looking for, having forgotten the pathname, then opened a terminal in this directory to use vi. On doing so, I noticed that at the end of the session there was a locked file called 4913 in the directory.

More experimentation showed several curious things. This is not a real file, since it does not show up in a directory listing (which is why I hadn’t spotted it before), and since it doesn’t exist, it can’t be deleted. However, it can be opened with another text editor such as gedit. If you do this, type in a character, and save, then the file takes on a real existence; it is no longer locked, and can be deleted in the usual way. Moreover, if you don’t do this but use vi again, the mysterious 4913 disappears; it seems to be toggled by the use of the editor.

A Google search for the number 4913 led me to a question someone had asked on StackExchange ten years ago. So this mystery has been known for ten years, and nobody, it seems, considered it worth doing anything about it in the intervening time. Well, I suppose that writing a non-existent locked file isn’t really a bug in the programme. But why 4913? I don’t know that!

However, lovers of numbers will no doubt have noticed that 4913 is a perfect cube.