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 >
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