directory order of files

directory order of files

[Edmund GRIMLEY EVANS]

With Linux ext2, and some other systems, when you create files in a
new directory, the file system remembers their order:

$ mkdir new
$ cd new
$ touch one two three four
$ ls -U
one  two  three  four

(1) Is there any standard that says a system should behave this way?
Is there any software that depends on this behaviour?

(2) Are there Linux file systems that don't work this way? Maybe
someone with a mounted writable reiserfs could do a quick check.

Please copy replies to me as I am not subscribed. Thanks.

Edmund

Re: directory order of files

[Hans Reiser]

Edmund GRIMLEY EVANS wrote:
> 
> With Linux ext2, and some other systems, when you create files in a
> new directory, the file system remembers their order:
> 
> $ mkdir new
> $ cd new
> $ touch one two three four
> $ ls -U
> one  two  three  four
> 
> (1) Is there any standard that says a system should behave this way?
> Is there any software that depends on this behaviour?

Unix filesystem hierarchies are defined to be a partial ordering, not a full ordering.

> 
> (2) Are there Linux file systems that don't work this way? Maybe
> someone with a mounted writable reiserfs could do a quick check.
> 
> Please copy replies to me as I am not subscribed. Thanks.

bash-2.05# mkdir fu
bash-2.05# cd fu
bash-2.05# touch one two three four
bash-2.05# ls -U
one  two  four	three

Hans

Re: directory order of files

[Alan Cox]

> With Linux ext2, and some other systems, when you create files in a
> new directory, the file system remembers their order:

No - it merely seems too. 

> $ touch one two three four
> $ ls -U
> one  two  three  four

Then try 'rm three; touch five'

> 
> (1) Is there any standard that says a system should behave this way?
> Is there any software that depends on this behaviour?

The order is arbitary. 

Re: directory order of files

[Alexander Viro]

On Fri, 29 Jun 2001, Alan Cox wrote:

> > With Linux ext2, and some other systems, when you create files in a
> > new directory, the file system remembers their order:
> 
> No - it merely seems too. 
> 
> > $ touch one two three four
> > $ ls -U
> > one  two  three  four
> 
> Then try 'rm three; touch five'

Moreover, it isn't true even for the case when we create a list of files
in empty directory. Example: assuming that /tmp has 1Kb blocks,

mkdir /tmp/A
cd A
touch `perl -e 'print "a"x255'`
touch `perl -e 'print "b"x255'`
touch `perl -e 'print "c"x255'`
touch `perl -e 'print "d"x255'`
touch A
ls -U

will give you (lots of a) (lots of b) (lots of c) A (lots of d).

With 4Kb blocks you'll need 16 long names instead of 4 - the effect
will be the same.

The reason is quite simple - at some point you get no space for long
name and it goes into the next directory block, but there's still enough
for a short name, so it gets created in the first block.

IOW, there's no warranties at all.

Re: directory order of files

[lk]

on reiserfs ls -U show soething like:

one two four three





On Fri, 29 Jun 2001, Edmund GRIMLEY EVANS wrote:

> With Linux ext2, and some other systems, when you create files in a
> new directory, the file system remembers their order:
>
> $ mkdir new
> $ cd new
> $ touch one two three four
> $ ls -U
> one  two  three  four
>
> (1) Is there any standard that says a system should behave this way?
> Is there any software that depends on this behaviour?
>
> (2) Are there Linux file systems that don't work this way? Maybe
> someone with a mounted writable reiserfs could do a quick check.
>
> Please copy replies to me as I am not subscribed. Thanks.
>
> Edmund
> -
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