topic Edit a file without changing the inode number in Operating System - Linux

Edit a file without changing the inode number

MathanSankar — Tue, 20 Mar 2007 00:32:45 GMT

When u edit a file in unix the inode number changes.
Is there any way to edit a file without changing the inode number???

Re: Edit a file without changing the inode number

Stuart Browne — Tue, 20 Mar 2007 01:05:52 GMT

Hrm, weird. Never knew that one..

Quick (hack) fix: Make a hard-link to it ('ln '). As the inode reference count will be > 1, it won't destroy the file, and re-create it, it'll use the in-place inode (as it's referenced).

That being said, I guess it depends on the editor you use, or what you're trying to do with the file.

What editor do you use? (I tested with 'vim').

Re: Edit a file without changing the inode number

MathanSankar — Tue, 20 Mar 2007 03:46:18 GMT

Thanks stuart... It works...

Re: Edit a file without changing the inode number

Hein van den Heuvel — Tue, 20 Mar 2007 08:56:11 GMT

I think it would depend a bunch on the exact implementation of the editor chosen, and some 'luck' as well.

What Linux? What version? What Editor?

For details on what the editor exactly does use 'strace editor small-file' and study the lines after the exit commands. (Watch in horror all the 'stuff' that is being done before you get control of thr screen! :-)

Here, on my dinky 'thin client' with a Linux 2.4.25 theeditor of choice is vi and is implemented in busybox. The output file is created as:

open("xy", O_WRONLY|O_CREAT|O_TRUNC, 0664) = 3
write(3, "....

So if anything goes wrong, the data is destroyed already.
I could imagine other editors, perhaps doing a create on a new output file first, using a unique temp name, and then when this is succesfully write rename it to the real output, blowing away the original implicitly or explicitly with unlink.

Hope this helps,
Hein van den Heuvel