[comp.unix.wizards] what does the link count of a directory show?

mkhaw@vaxc.UUCP (05/20/87)

What does the "link count" shown by "ls -ld" mean for a directory?
Is it the same for SysV and 4bsd?

Mike Khaw
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pdb@sei.cmu.edu.UUCP (05/20/87)

In article <12913@vaxc.ARPA> mkhaw@vaxc.ARPA (Michael Khaw) writes:
>What does the "link count" shown by "ls -ld" mean for a directory?
>Is it the same for SysV and 4bsd?

At least on 4bsd, the link count for a directory is exactly that.  Even
though users can't link directories, mkdir(2) does it all the time.  The
special entries '.' and '..' in a directory are links to itself, and it's
parent, respectively.  If a directory has many subdirectories, it is possible
for it's link count to be very large.

--Pat.

arosen@ulowell.cs.ulowell.edu (Andy Rosen) (05/20/87)

In article <12913@vaxc.ARPA> mkhaw@vaxc.ARPA (Michael Khaw) writes:
>What does the "link count" shown by "ls -ld" mean for a directory?
>Is it the same for SysV and 4bsd?

It's just like for a file.  It'll always (hopefully) be at least two.  One for
the directory itself, and one for ".".  It's increased by one every time a
sub-directory is added in it (for "..").  For what it's worth, you can tell
how many sub-directories a directory has even if you can't look at the
directory by looking at the link count.

It's the same for SysV and BSD.

-- 
Andy Rosen         | ulowell!arosen | ************* | "I got this guitar and I
ULowell, Box #3031 |                | * RD in '88 * |  learned how to make it
Lowell, Ma 01854   |                | ************* |  talk" -Thunder Road

merlin@hqda-ai.UUCP (David S. Hayes) (05/21/87)

     The link count for a directory has the same meaning as the
link count for a file.  It indicates how many names there are for
the directory.

     Every directory has at least two different names:

     from above:    	 parent/directory
     from 'directory':	 .

If there are subdirectories, each of them adds another link:

     from below:    	 subdir/..

It is even possible to create additional links to directories:

     ln directory link

This option is restricted to root, and requires the -f (force)
switch to prevent accidental use.
-- 
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