Hi Ronni Thanks for that. To test the process I ran the Terminal command on each iMac citing copies of the same file on each (assumed to have good data). And got the same checksum, as expected. But this is not a practical process to run against every file copied! Hence my search for an inbuilt and automatic procedure.
> When you copy files from one location to another in OS X, the system should > run a number of checks to validate the data and ensure that it was copied > correctly; however, if you are using third-party utilities to copy a file, > you might be concerned about potential corruption. I assume that OSX runs the validation routine for copies made on the one computer, not on files copied across a network to another computer via AirDrop. If so, why not? Downloaded software updates etc often have an end-to-end validation routine built in. It was the fully Apple process (not a third party app) that apparantly introduced the data problem I had a few days ago. > Most file copying processes will run special "checksum" routines on files > that are being copied, which is a quick way to summarise the bits and bytes > in a file to give it a unique signature code that can be used to verify its > integrity. I've never come across a message warning of possible integrity problems. My file had failed in one obvious aspect while the second re-transmission was satisfactory. Just to complete the process, it may have been nice to run the Terminal routine to confirm there was a disparity in the checksums. So, did I just have that one in a billion-billion data hiccup? Please excuse my rant! I've obviously got too much time on my hands. Cheers Alan On 23/05/2013, at 2:44 PM, Ronni Brown <[email protected]> wrote: > Hi Alan, > >> Is there an App, or a Finder setting, to verify the integrity of copied data >> in individual files? > > You don'e require an App, you only need to run a command in Terminal.app. > > When you copy files from one location to another in OS X, the system should > run a number of checks to validate the data and ensure that it was copied > correctly; however, if you are using third-party utilities to copy a file, > you might be concerned about potential corruption. > > Most file copying processes will run special "checksum" routines on files > that are being copied, which is a quick way to summarise the bits and bytes > in a file to give it a unique signature code that can be used to verify its > integrity. > > In addition, Apple's default file-system format includes a journal, which > caches file writes before they are made permanent on the disk and therefore > greatly reduces potential corruption from write interruptions such as power > failures. > > Because of this, manual verification of files is not needed; however, if > desired, it can be done. > > There are several ways you can manually check the integrity of a copied file. > Two approaches involve checking the folder structure against the original to > see if any files are missing, and if all have been copied, then verifying the > integrity of the copied files. > > As your question is about a single file, I will only give instructions and > the command to verify the integrity of an individual file. > > Validating individual files > To verify each file, you will need to run a checksum on it and then compare > the checksums. > > To do this for a single file. > Open Terminal > Type the command "md5" (or "md5 -q" to only show the checksum itself) in > Terminal followed by a single space. > Then drag the first copy to the Terminal window (this should enter a full > path to the file) and then press Enter to execute the command. > > Run the same command on the copied file. > > To show you what it looks like in Terminal, I ran the md5 -q command on a mp4 > video file. > The original file is in my Movies folder, the Copied file is on my desktop. > > Last login: Thu May 23 14:16:57 on ttys000 > Ronni-MacBook-Pro:~ ronni$ md5 -q /Users/ronni/Movies/RealPlayer\ > Downloads/Instructions\ for\ loading\ your\ Dymo\ LabelWriter\ printer\ from\ > LabelValue.mp4 > 832442d573c3b7d164d041df08ec5026 > Ronni-MacBook-Pro:~ ronni$ md5 -q /Users/ronni/Desktop/Instructions\ for\ > loading\ your\ Dymo\ LabelWriter\ printer\ from\ LabelValue.mp4 > 832442d573c3b7d164d041df08ec5026 > Ronni-MacBook-Pro:~ ronni$ > > In my example above, the two files show the same checksums indicating they > are the same (no corruption). > > > Cheers, > Ronni > > 17" MacBook Pro 2.3GHz Quad-Core i7 “Thunderbolt" > 2.3GHz / 8GB / 750GB @ 7200rpm HD > > OS X 10.7.4 Lion > Windows 7 Ultimate (under sufferance) > > > On 22/05/2013, at 10:59 AM, Alan Smith <[email protected]> wrote: > >> Is there an App, or a Finder setting, to verify the integrity of copied data >> in individual files? >> >> My immediate concern is to check the integrity of EyeTV exports moved from >> one Mac to another, but since discovering a corrupt file, I now have >> concerns about all files I copy, including backups via Time Machine and >> SuperDuper. >> >> My EyeTV source file is on the main iMac (late 2012 - 27inch) and >> destination is a Firewire external hard drive attached to a second "media" >> iMac (late 2009 - 21.5 inch). Both iMacs have Mountain Lion OS. To >> complicate the issue, the file is copied twice to get it to its destination. >> It is not always obvious that the copied file is corrupt - it can be some >> time after the original has been deleted! >> >> My file transfer method: Ethernet does not work on the media Mac, so I use >> AirDrop. Typical example: I record an EyeTV program and export the edited >> clip to desktop on the main iMac. I then use AirDrop to copy it to the >> media Mac downloads folder (the default?). Next, the file is copied to a >> Firewire external drive and the link is finally Option-Copied to iTunes. I >> would normally delete the desktop file and the EyeTV original as soon as >> possible. (Then I watch the show via Apple TV!) >> >> I think AirDrop uses Mac-to-Mac WiFi and bypasses the Time Capsule. If so, >> this may cut out one potential problem with repeating wireless data. >> >> A secondary question: could I use AirDrop to copy the file in one step >> directly to the Firewire drive (and still apply a data integrity test)? >> >> Regards, Alan >> >> Alan Smith >> Late 2012 iMac 27" Intel Quad Core i5 3.2Ghz 8GB RAM - OSX 10.8.3 >> Late 2009 iMac 21.5" Intel Core 2 Duo 3.06GHz 12G RAM - OSX 10.8.3 >> iPad2; ATV2; iPhone5 >> > > -- The WA Macintosh User Group Mailing List -- > Archives - <http://www.wamug.org.au/mailinglist/archives.shtml> > Guidelines - <http://www.wamug.org.au/mailinglist/guidelines.shtml> > Settings & Unsubscribe - > <http://lists.wamug.org.au/listinfo/wamug.org.au-wamug> -- The WA Macintosh User Group Mailing List -- Archives - <http://www.wamug.org.au/mailinglist/archives.shtml> Guidelines - <http://www.wamug.org.au/mailinglist/guidelines.shtml> Settings & Unsubscribe - <http://lists.wamug.org.au/listinfo/wamug.org.au-wamug>
