Very Computer

I recently came across a situation wherein an effort has to be made
to change the modification time  of the symbolic link (NOT the file
that it points to!) to a different time other than the current time.

utimes() / touch changes the file being pointed to ...

Any hints ? ?

Thanks

--

Prasanna

Sorry but you cannot change the modification time on a symbolic link
without changing the inode, which changes all links to that inode.

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Sorry but you cannot change the modification time on a symbolic link
without changing the inode, which changes all links to that inode.

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Greatest Movie Quote of all time:

I love the smell of Napalm in the morning.  It smells like .... VICTORY!

------------------------------------------------------------------------

Applied Intelligence Group                    Phone: (405) 341-7700
501 East 15th Street, Suite 202                 Fax: (405) 341-8898
Edmond, OK  73013
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501 East 15th Street, Suite 202                 FAX:    405-341-8898
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For example, witness the following sequence of commands, typed on
SunOS 4.1.3:

        $ cd /tmp
        $ date > foo
        $ ln -s foo bar
        $ ls -li
        total 6
         33809 lrwxrwxrwx  1 logan           3 Nov  7 20:25 bar -> foo
         33808 -rw-r--r--  1 logan          29 Nov  7 20:25 foo
        $ cat bar
        Tue Nov  7 20:25:02 PST 1995
        $ cat foo
        Tue Nov  7 20:25:02 PST 1995
        $ exit

Notice that "bar" and "foo" have separate i-node numbers.  (See the
first column in the output of "ls -li".)

Anyway, the reason you can't change stuff about the symbolic link is
that the functions which operate on the file automagically expand the
symbolic link into the file to which it refers before doing the
requested operation.  So, in the above example, if you want to set the
modification date of "bar", you do a 'utimes ("/tmp/bar", NULL)'.  The
utimes() call (or some other system thingy) translates the "/tmp/bar"
into (effectively) "/tmp/foo" and blithely does the operation on it.

In other words, what you need is an lutimes() call, just like there
is an lstat() call in addition to stat().

Incidentally, I think I remember coming across a Unix which behaves the
other way by default -- it changes the link's time rather than the file
linked to.  However, I don't remember which kind of Unix that was.

Hope this helps...

   - Logan
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Bill> From looking at my home directory, apparently it's possible to have a
Bill> symbolic link to a file which doesn't even exist (I've got a .homepage,
Bill> but I haven't put anything in it yet).

Yes, in fact, I knew someone who was considering using that to
manage his to-do list:

        ln -s "take out the trash" 1 (priority 1)
        ln -s "feed the dog" 2 (priority 2)
        ls -l (shows the current listing)
        mv 1 3 (change priority)
        ls -l (new listing)
        rm 3 (been there, did that!)

Truly, truly, an abuse of the Unix filesystem.  But hey, cool!

Just another Unix hacker,
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Web: <A HREF="http://www.teleport.com/~merlyn/">My Home Page!</A>
Quote: "I'm telling you, if I could have five lines in my .sig, I would!" -- me

| Yes, in fact, I knew someone who was considering using that to
| manage his to-do list:
|
|       ln -s "take out the trash" 1 (priority 1)
|       ln -s "feed the dog" 2 (priority 2)
|       ls -l (shows the current listing)
|       mv 1 3 (change priority)
|       ls -l (new listing)
|       rm 3 (been there, did that!)
|
| Truly, truly, an abuse of the Unix filesystem.  But hey, cool!

It works for only a maximum of nine tasks at a time, though, unless
you pipe ls -l to sort -n with the appropriate keyfield.

Well, ten tasks if you start numbering from zero.

Exactly.

He's using symbolic links as a quick list.  By creating bogus links
to ascii text he'll see the text any time he does an ls -l, which
would be a pretty good reminder.  By rm'ing one of them, in all
likelihood he/she remembered to do that thing.

By numbering 1,2,3,... they'll show up in the ls listing in that order.

Joe

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okay, I finally arrived at the gate now. Next time, I'll check
my ticket more closely.

Quote:>The problem with what you are trying to do is that a symbolic link shares
>an inode with the original link. and the inode contains the date
>information.  In order to change the modification time of a link, the
>link must have its own inode.  This translates into a "hard" link.

>Sorry but you cannot change the modification time on a symbolic link
>without changing the inode, which changes all links to that inode.

--
"Goodness me, could this be industrial disease?"  Dire Straits

Quote:>Yes, in fact, I knew someone who was considering using that to
>manage his to-do list:

Quote:>    ln -s "take out the trash" 1 (priority 1)
>    ln -s "feed the dog" 2 (priority 2)
>    ls -l (shows the current listing)
>    mv 1 3 (change priority)
>    ls -l (new listing)
>    rm 3 (been there, did that!)

>Truly, truly, an abuse of the Unix filesystem.  But hey, cool!

Quote:>|   ln -s "take out the trash" 1 (priority 1)
>|   ln -s "feed the dog" 2 (priority 2)
>|   ls -l (shows the current listing)
>|   mv 1 3 (change priority)
>|   ls -l (new listing)
>|   rm 3 (been there, did that!)
>It works for only a maximum of nine tasks at a time, though, unless
>you pipe ls -l to sort -n with the appropriate keyfield.
>Well, ten tasks if you start numbering from zero.

Appropriately, "!" would be the highest priority.

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UniSoft Limited, London, England.

Quote:>Appropriately, "!" would be the highest priority.

-zefram