Re: [Haskell-cafe] Behaviour of System.Directory.getModificationTime
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 On 12/17/10 06:22 , Arnaud Bailly wrote: Thanks for your answers. I am a little bit surprised, I thought timestamps were on the milliseconds scale. POSIX timestamps are seconds. - -- brandon s. allbery [linux,solaris,freebsd,perl] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon university KF8NH -BEGIN PGP SIGNATURE- Version: GnuPG v2.0.10 (Darwin) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAk0Ss28ACgkQIn7hlCsL25XpygCgziZm1KyO+dP00ACtIrfsueJg 0dQAoI6hNz3oSmiIO2kAiXtRmowWwAg1 =wAHu -END PGP SIGNATURE- ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Behaviour of System.Directory.getModificationTime
Thanks for your answers. I am a little bit surprised, I thought timestamps were on the milliseconds scale. @Krzysztof: Yes, you are right, an event-based interface is far superior to the basic polling approach I took. At present, a couple seconds granularity is fine with my use case so I don't care too much getting more precise notifications, but I'd rather be notified by the kernel than going through the hassle of polling it myself. I played a bit with inotify (through a Java binding) a year ago and found it a bit cumbersome to wield as one has to monitor explicitly all nodes in a tree. Maybe I am wrong. Moreover, I am not aware of a portable way of doing this. I would appreciate pointers and advices on these matters. Thanks again, arnaud 2010/12/16 Krzysztof Skrzętnicki gte...@gmail.com: If this is not a toy program I would really suggest using something that is builtin in the OS of choice. On Linux there is inotify (http://en.wikipedia.org/wiki/Inotify), but I'm pretty sure that other OSes have similar interfaces. The modification time method seems really fragile and I probably not very efficient as well. Best regards, Krzysztof Skrzętnicki On Thu, Dec 16, 2010 at 17:50, Arnaud Bailly arnaud.oq...@gmail.com wrote: actually, IRL the code works as expected. Might it be possible that the speed of test execution is greater than the granularity of the system's modification timestamp? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Behaviour of System.Directory.getModificationTime
actually, IRL the code works as expected. Might it be possible that the speed of test execution is greater than the granularity of the system's modification timestamp? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Behaviour of System.Directory.getModificationTime
Yes, modification times are reported in seconds, so you'll have to wait on average 0.5s for a file change to be visible via the modification date. Due to buffers and filesystem optimisations it might even take longer. On 16 December 2010 16:50, Arnaud Bailly arnaud.oq...@gmail.com wrote: actually, IRL the code works as expected. Might it be possible that the speed of test execution is greater than the granularity of the system's modification timestamp? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Push the envelope. Watch it bend. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Behaviour of System.Directory.getModificationTime
If this is not a toy program I would really suggest using something that is builtin in the OS of choice. On Linux there is inotify ( http://en.wikipedia.org/wiki/Inotify), but I'm pretty sure that other OSes have similar interfaces. The modification time method seems really fragile and I probably not very efficient as well. Best regards, Krzysztof Skrzętnicki On Thu, Dec 16, 2010 at 17:50, Arnaud Bailly arnaud.oq...@gmail.com wrote: actually, IRL the code works as expected. Might it be possible that the speed of test execution is greater than the granularity of the system's modification timestamp? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Behaviour of System.Directory.getModificationTime
Hello, I am writing a program which scans a bunch of directories to detect changes (added, modified, deleted files). To detect modification, I would like to use getModification, doing something like the following: -- |Stores last modified timestamp of the file -- Yes, I come from Java... type HashMap = M.Map FilePath ClockTime data (Show a, Eq a) = Edit a = Mod a | Add a | Del a deriving (Eq,Show) checkChanges :: [String] - HashMap - IO ([Edit FilePath], HashMap) checkChanges [fs] m = do addedFilesList - lsRecursive fs timestamps - mapM getModificationTime addedFilesList let allts = zip addedFilesList timestamps let ret = (findDeletedFiles allts.updateScannedFiles allts) ([],m) return ret -- | Returns an updated map and a list of modified/added/deleted files updateScannedFiles :: [(FilePath,ClockTime)] - ([Edit FilePath], HashMap) - ([Edit FilePath], HashMap) updateScannedFiles []r = r updateScannedFiles ((path,ts):files) (updates,m) = case M.lookup path m of Nothing - updateScannedFiles files ((Add path:updates), M.insert path ts m) Just ts' - if ts' ts then updateScannedFiles files ((Mod path:updates), M.adjust (const ts) path m) else updateScannedFiles files (updates, m) -- omitting findDeletedFiles which is obvious and works I got the following test case that fails: recursively marks changed files as modified `for` do complexFileSetup -- create a small FS tree with 3 files root - tempDir state - checkChanges [root] M.empty writeFile (root / subdir / cFile.txt) this is another toast checkChanges [root] (snd state) = (\r - assertEqual there should be 1 changed file in 3 files 1 ((length.modified.fst) r)), In words: the getModificationTime of the overwritten file appears identical before and after the write. What am I doing wrong ? BTW, I checked the content of the file which has been correctly updated. Thanks for your help Arnaud ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
