How to monitor modify a file

Is there a way to get a file has been modified notification.
I found there is a Linux inotify, this thing on iphone handy it.
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Just find the kqueue, heroes who can provide a sample code.
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I know seems to have a delegate method UISearchBar inside, you can always know that there is no change, I think we can refer to the following
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Write a timer. . . The following documents are comparing hash value can not every time?

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live file api hook