Re: purpose of "." entry in a diretory

[dabicho <tsukebumi@xxxxxxxxx>]

On Apr 8, 2005 4:14 PM, Greg Freemyer <greg.freemyer@xxxxxxxxx> wrote:
> On Apr 8, 2005 4:43 PM, Jason Zheng <xin.zheng@xxxxxxxxxxxx> wrote:
> > Manu Jose wrote:
> >
> > >Hi Jason,
> > >               "." represents the current working directory and ".."
> > >represents the parent directory of the current working directory . It
> > >is useful in various contexts. For example if u r currently in the
> > >directory /mnt/foo and want to copy the content of /mnt/foo1 to
> > >/mnt/foo just isuue the command " cp -R /mnt/foo1/* . "  .So it is
> > >always good to represent the working directory with a short symbol and
> > >it is not at all a waste....
> > >
> > >Manu
> > >
> > >--
> > >Kernelnewbies: Help each other learn about the Linux kernel.
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> > >
> > >
> > >
> > >
> > Let me rephrase my question a little bit: BESIDES the obvious usage of
> > "." entry, in terms of the filesystem, what is the purpose of "." entry?
> >
> > The obvious answer is that you can refer to the current directory using
> > "./", however, in order to look up the "." entry, the kernel must have a
> > knowledge of the current directory in the first place, doesn't it? The
> > kernel needs the directory table for the current directory to look up
> > which inode the "." entry refers to. Doesn't that seem a little
> > redundant, since the kernel already knows what the current directory is?
> > If the kernel is already caching the current directory table, it might
> > as well just cache the current directory's inode.
> >
> > Coming back to my original question, does the kernel really need that
> > "." entry? or is it purely for the user convenience?
> >
> > cheers,
> >
> > jz
> >
> Jason,
> 
> I thought about your question when you first asked it, and again now.
> In a generic sense I can't think of a reason that the '.' entry is
> mandatory.  As you say there seem to be ways to track the same info
> without have that specific directory entry.
> 
> OTOH, I would assume the VFS (virtual file system) component of the
> Linux Kernel assumes that it is there.
> 

I thought about your question when you first asked it, and again now.
In a generic sense I can't think of a reason that the '.' entry is
mandatory.  As you say there seem to be ways to track the same info
without have that specific directory entry.

OTOH, I would assume the VFS (virtual file system) component of the
Linux Kernel assumes that it is there.

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