Unix directories

Re: Unix directories

On the wall of the virtual bathroom stall, "Alex" <Reply_To_Newsg [email protected]> scratches:[color=blue]
> I've just noticed that directories in Unix have different sizes whereas in
> Windows they don't.
> Why is this so?
>[/color]

because in UNIX the directory is itself a special file. It's size is
proportional to the number of files in the directory.

Re: Unix directories

Not sure if I agree that windoz has fixed size directories. What is your
evidence.
The root directory seems to have a limit of the number of files you can put
in it, but
that seems to not be true of other directories. In unix the number of
directory entries
and files for that matter is limited by the number of inodes that were
created for the filesystem
isn't it?

"Wiseguy" <noone@celeron. local> wrote in message
news:3f4d844b_3 @127.0.0.1...[color=blue]
> On the wall of the virtual bathroom stall, "Alex"[/color]
<Reply_To_Newsg [email protected]> scratches:[color=blue][color=green]
> > I've just noticed that directories in Unix have different sizes whereas[/color][/color]
in[color=blue][color=green]
> > Windows they don't.
> > Why is this so?
> >[/color]
>
> because in UNIX the directory is itself a special file. It's size is
> proportional to the number of files in the directory.
>[/color]

Re: Unix directories

"Alex" == Alex <Reply_To_Newsg [email protected]> writes:

Alex> I've just noticed that directories in Unix have different
Alex> sizes whereas in Windows they don't. Why is this so?

A Unix directory is just a file that contains an entry for each
element contained in it. The more files or subdirectories (inodes) in
it, the larger the size.

I don't know the Windows file system architecture so I can't tell you
anything new about it.

I'm very curious as to why you chose to post this question to a Java
group?

Cheers!
Shyamal

Re: Unix directories

On 28 Aug 2003 08:48:54 -0500, Shyamal Prasad <shyamal.prasad @ericsson.com>
two-finger typed:
[color=blue]
> "Alex" == Alex <Reply_To_Newsg [email protected]> writes:
>
> Alex> I've just noticed that directories in Unix have different
> Alex> sizes whereas in Windows they don't. Why is this so?
>
>A Unix directory is just a file that contains an entry for each
>element contained in it. The more files or subdirectories (inodes) in
>it, the larger the size.
>
>I don't know the Windows file system architecture so I can't tell you
>anything new about it.[/color]

Windows hides the information on the number of sectors that are used to
represent a directory.
The only information you can get about a directory, is the number of files
in it. There is no way to gain more information about the number of blocks
used for the directory entries, unless you access the file system on a
lower level (assembly language or special libraries).

(the following assumes a FAT or FAT32 file system...)
Programs like Norton Speedisk are able to see that low and can recover lost
space from directory nodes where there are a lot of deleted files. It
compresses those directory entry blocks, loosing the ability to undelete
the files that used to be in there in the process (unless you use the
Norton Protected Recycle Bin - which even keeps deletion of files from
recovering the blocks they used - until more room is needed, anyway).

Another, manual way to recover those blocks is by moving the files and
subdirectories to a new directory, deleting the old one, and then renaming
the new directory to the old name. You would only do this if you had
thousands of files in the directory, that were subsequently moved or
deleted.
[color=blue]
>
>I'm very curious as to why you chose to post this question to a Java
>group?
>
>Cheers!
>Shyamal
>[/color]

Especially, since this kind of information is at a level that the standard
java libraries cannot get at.

Cheers.

Re: Unix directories

I was looking this up on the web (liars database) and it SEEMS
that on windows the NTFS file system has directories as B trees
so they can grow, and the FAT file system has directories stored
as normal files so they can grow too (except the root maybe).

Phil...

"Alex" <Reply_To_Newsg [email protected]> wrote in message
news:bijvgb$hdm [email protected] .warwick.ac.uk. ..[color=blue]
> I've just noticed that directories in Unix have different sizes whereas in
> Windows they don't.
> Why is this so?
>
> Thanks.
> Alex.
>
>[/color]

Re: Unix directories

I discovered the fact while writing an 'Explorer style browser' in java and
the size field wasn't 0 for directories in linux.

I haven't tried this yet but since directories and links are files in Linux
does this mean that I can reproduce them by writing data to a new file? or
do I have to set certain lower level bits to do this?

"Shyamal Prasad" <shyamal.prasad @ericsson.com> wrote in message
news:yzshe41yjs p.fsf@ericsson. com...[color=blue]
> "Alex" == Alex <Reply_To_Newsg [email protected]> writes:
>
> Alex> I've just noticed that directories in Unix have different
> Alex> sizes whereas in Windows they don't. Why is this so?
>
> A Unix directory is just a file that contains an entry for each
> element contained in it. The more files or subdirectories (inodes) in
> it, the larger the size.
>
> I don't know the Windows file system architecture so I can't tell you
> anything new about it.
>
> I'm very curious as to why you chose to post this question to a Java
> group?
>
> Cheers!
> Shyamal
>
>[/color]

Re: Unix directories

On Fri, 29 Aug 2003 09:10:43 +0200, "Alex" <Reply_To_Newsg [email protected]>
two-finger typed:
[color=blue]
> I discovered the fact while writing an 'Explorer style browser' in javaand
>the size field wasn't 0 for directories in linux.
>
>I haven't tried this yet but since directories and links are files in Linux
>does this mean that I can reproduce them by writing data to a new file? or
>do I have to set certain lower level bits to do this?
>[/color]

The latter. Dispite the fact that the content of the blocks on the harddisk
is almost the same for files and directories, it's the chmod bits that make
the difference.
The OS commands and libraries make sure that this does not get confused
(i.e. you can't normally change a directory into a file, or read from the
directory with normal file operations).

Cheers.