UNIX for Advanced & Expert Users

@fpmurphy,

Thanks for the reply. However this appears to be a symbolic soft link. I am in search of a hard link example on RHEL.

Code:

[root@jralph-linux ~]# ls -ali /bin/ed /bin/red
15237230 -rwxr-xr-x 1 root root 49344 Oct 10  2008 /bin/ed
15237134 lrwxrwxrwx 1 root root     2 Jul 16 11:09 /bin/red -> ed

jaysunn

Hard links are harder to spot since they don't tell you where they all are.

One use I've abused hard links for is renaming a file that's being written to. Since the file still exists through all points in the process, and nothing like cp that reads the file is used, nothing bad happens:

Code:

some-long-running-process > hugrfile &
# ...whoops, I wanted hugefile, not hugrfile.
ln hugrfile hugefile
# hugrfile and hugefile are now the same file
rm hugrfile
# Now only hugefile exists.  The file has been renamed with no interruption
# to "some-long-running-process"

Another use for hard links would be when you have a file that needs to be edited by several different people who don't all have access to the directory it's in. Create a hard link in a directory they do have access to and voila. A symbolic link would fail here, since whoever opens it would still need access to the real file.

OK, fired up my old RHEL5.3 harddisk and had a look for hard links. The following hard links exists in /usr/bin

Code:

-rwxr-xr-x  2 root root       20044 Jan  5  2009 iconvconfig
-rwxr-xr-x  2 root root       20044 Jan  5  2009 iconvconfig.i686

Awesome,
Thanks so much for all the great answers. I understand hard links fully now.


jaysunn

A couple very common examples of hard links being used in an O/S which is not specific to any version:

. is a hard link to the current directory.
.. is a hard link to the parent directory.

In an "empty" directory, "." will have 2 links. The actual directory named file in the parent directory will be one of those links, the other is the dot itself. As you create subdirectories, each of those will get a ".." entry which will be another hard link to the current directory.

Easy example for you to try on your own. Create a direcotry, cd to it, ls -lai, create a direcotry, ls -lai again.