Very Computer

Steve

If you're talking about hard links, well, you're right. A hard link is just
a directory entry that happens to point at the same inode as another one.
The inode does store the number of hard links, but not which directory entry
points to it. To find all of the directory entries, you're probably going to
have to search the entire filesystem. :(

Travis Geiselbrecht

:I apologize if this is the wrong group for this question. Just
:direct me to the right place, thanks. The questions concerns
:symbolic links. A file entry keeps track of how many symbolic links
:are attached to it.

No.  There is nothing that keeps track of the number of symbolic links.
The st_nlink field in the stat structure counts only hard links.
Maintaining a count of symbolic links would be sort of like trying to
keep track of how many people have a record of your e-mail address.

: Am I correct in assuming that it has no
:information on where those links are located? I am trying to write
:a little utility that takes a file and tells me if and where all
:the links to it are located.

Good luck.  The only way to do it is to traverse the entire directory
tree starting from the root file system.  Also, keep in mind that if the
file system is exported, e.g. via NFS, the symlink might be on
another system.  Or, the symlink might be on a file system that is not
currently mounted, such as a floppy disk in someone's desk drawer.

--


PGP public key 1024/9A9C7955
Key fingerprint = 2F E5 82 F8 5D 06 A2 59  20 65 44 68 87 EC A7 D7

Stop. No it doesn't. There is a count of hard links in the inode. There
is nothing in the file entry. Either you don't understand the UNIX
filesystem model or you type even worse than I do ;-)

Hard links point to an inode. An inode counts the links. The inode
describes the file. Symbolic links contain a pathname, it may point to
a file, directory, device, pipe or be invalid, and nothing keeps track
of where slinks point. Slinks are only evaluated when used, and then
only in the forward lookup direction, with absolutely no back pointers
at all.

--

 "If I were a diplomat, in the best case I'd go hungry.  In the worst
  case, people would die."
                -- Robert Lipe

Quote:>Am I correct in assuming that it has no
>information on where those links are located? I am trying to write
>a little utility that takes a file and tells me if and where all
>the links to it are located. Any help is greatly appreciated.

jue
--
Jrgen Exner; jurgenex AT microsoft.com
Sorry for this anti-spam inconvenience

there is no chance to find all symlinks pointing to a file. Assume a NFS
mounted filesystem from machine A mounted on machine B (/nfsmount/.....)
and a symlink on a local disk of B pointing to some file in
/nfsmount/... A will NEVER find out about this link, because its not
accessible for A.

Regards, Kurt

Sorry, the number of hard links is not kept in "A file entry," it lives
in the inode. people have this vision of "a file" and "a link to the
file," but all directory links to an inode are equal.

--

 "If I were a diplomat, in the best case I'd go hungry.  In the worst
  case, people would die."
                -- Robert Lipe

It can be done on the fly. Find the inode number of the file in question:

 518231 stuff

/home/michael/stuff

find <mount point of filesystem> -inum <inum of file> -print
prints all the files with the corresponding inode number.

HTH, M.

--
Michael ``M.'' Brown
Computer Science, University of Waterloo
SIGSIG -- signature too long (core dumped)

However if I'm not mistaken the original poster was looking for a general
approach that will allow him to get all filenames for _every_ file.
Using your suggestion with find will require a cost of O(n^2).
Using some programming and your own cross-reference matrix can get this cost
of HD access down to a linear factor of O(n).

On a filesystem with let's say 5000 files this is the difference between 1
minute and 3 1/2 days!!!

jue
--
Jrgen Exner; jurgenex AT microsoft.com
Sorry for this anti-spam inconvenience

| It can be done on the fly. Find the inode number of the file in question:

|  518231 stuff

| /home/michael/stuff
|
| find <mount point of filesystem> -inum <inum of file> -print
| prints all the files with the corresponding inode number.

And you can use the -lname option on everything to find symbolic links,
although there's obviously no promise that you will find ALL slinks,
since some may be in filesystems not mounted on your system.

Oh, and you might use "df" as a convenient cheat to find that mount
point.

--

 "If I were a diplomat, in the best case I'd go hungry.  In the worst
  case, people would die."
                -- Robert Lipe