How to use md5 Checksums to verify thousands of copied files

This should cover what you're looking for: http://reviews.cnet.com/8301-13727_7-57575414-263/how-to-manually-verify-copied- files-in-os-x/

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cd /pathtofolder; for filename in `ls`; do md5 $filename; done

cd to the folder containing the files and then perform md5 checksum on all the files within.

Tophers' link provides a more logical bash argument, where folder_path is adjusted accordingly:

find -s FOLDER_PATH -type f -exec md5sum {} \; | md5sum

The commercial application "Carbon Copy Cloner" can do a checksum comparison between corresponding files in two folders. I would use that, rather than screwing around with shell commands. I believe it has a free demo.

I cover how to do that in the link above, but to quickly do this, run the following command on both folder paths:

find -s ~/Downloads -type f -exec md5 -q {} \; | md5

This will generate a list of md5 checksums for each file in the directory (in this case, the Downloads directory in your home folder, but you can change this to whatever you would like), and then create a summary checksum of the collective checksums.

In my case, the above command yields the following checksum:

42cf9632cf763cad84c633f0cc7c93bb

Doing this on my Documents folder yields the following checksum:

782845544f0ecf8a7ae5fa66197d6abd

You can then compare these to see if they are different. In this case they are, indicating the folders do not have the same contents.

Keep in mind this may take a while to run, as checksums will have to be computed for each file in the directory. While this is a raw command, you can save it in a script and then simply run the script with an input argument to make it easier. For example, the following script should work:

#!/bin/bash

find -s $1 -type f -exec md5 -q {} \; | md5

Saving this in a text file, naming it something like "dirsum" and then making it executable in a path location such sa /bin (or a custom added path) will make it easily accessible, so you can run the same command by simply typing the following in the Terminal (in this case to calculate a checksum of the Downloads folder):

dirsum ~/Downloads

Just a quick change, instead of the $1 in the command above, use "$@" (including quotes) to properly handle folders with spaces in their names, so the command in the script looks like the following:

find -s "$@" -type f -exec md5 -q {} \; | md5

What are the two commands specifically that you are running? Some examples of how it should be run are the following:

For the Downloads folder in your home directory:

find -s ~/Downloads -type f -exec md5 -q {} \; | md5

For the Movies folder in your home directory:

find -s ~/Movies -type f -exec md5 -q {} \; | md5

For the Applications > Utilities folder:

find -s /Applications/Utilities -type f -exec md5 -q {} \; | md5

For the entire file system:

find -s / -type f -exec md5 -q {} \; | md5

In some cases you may need to run the command with "sudo" in front of it (followed by supplying your password, when prompted), to ensure it has full access to the files in the directory. This is especially true for folders copied by other user accounts, or those in some system folders, and will look like the following:

sudo find -s /Users/username/Documents -type f -exec md5 -q {} \; | md5