Directory updation Notification?

Applications Programming
1

Hi,

I'm a UNIX newbie .. so forgive me if this question sounds dumb.
:slight_smile:

Is it possible for Unix to notify a process that a particular directory has been updated? Rather that the process constantly polling the directory ...

Awaiting your replies ..

Thanks,
VJ

2

I'm not sure what you mean exactly by "directory has been updated," but I'm pretty sure the answer is no. You would need a daemon (continuously-running background process) to check from time to time. This works OK if (1) performance is not critical and, (2) it's OK to have the notification delayed by a time interval up to X, where X is the period between the checks.

3

Hi Marc,

Thanks for your reply ..

What i meant by "directory has been updated" was whether a new file has been created in directory ...

Are there no SIGNALS provided by Unix for such a scenario ??
Maybe not ..

Thanks,
VJ

4

You can see that http://www-900.ibm.com/developerWorks/cn/linux/filesystem/dnotify/index.shtml

If you do not understand Chinese , I suggest you read the programe in middle of the article .

or ,please refer to LXR linux/Documentation/dnotify.txt

or ,you can click "the link" at the bottom of the article

5

Hi Chenhao,

That was a very informative link. Thanks !!

Is there an equivalent for this in UNIX? or do we have to write our own similar routines ..

Do reply.

Thanks again,
VJ

6

I agree, that was a very informative link. linux seems to have added some very interesting features.

But I also agree with Marc that standard unix does not have these features.

So you will need to write a monitoring program. Creating a new file entails writing to the directory that contains it. So your program should be able to open the directory, then loop doing a stat() system call and a sleep(). If the mtime of the directory changed, then someting happened. So then the program would scan the directory looking for a new file. This technique will have much less overhead than scanning the directory each loop.

7

Thanks Perderabo.

Will write some code then.

Thankyou all for the replies.
Good discussion!!

Regards,
VJ