Fastest way to check if two large files are identical

[Hacker]

Hi all,
What is the fastest way to check if two large files (eg. DVD or Blu-ray ISO images) are identical or not? Compare by contents is incredibly slow (even if I had enough memory), creating MD5 hashes for both files and comparing them instead is faster. Is there perhaps a way to create some hashes and compare them automatically (without AHK, etc.)? Or is there some other way to check if two files are identical that would be faster than compare by contents?

Thanks
Roman

[icfu]

Open files in HxD, press Ctrl+K...
http://mh-nexus.de/en/hxd/

Files aren't loaded into RAM, in opposite to the useless TC compare.

[Hacker]

icfu,
Will try, thanks.

Roman

[karlchen]

<disagree>

in opposite to the useless TC compare.

During the past few years, this useless file compare function has saved me a lot of working hours, because I frequently have to synchronize the contents of configuration files across a substantial number of Unix machines.
And this useless file compare function is quite good at comparing textfiles and allowing me to edit any difference on a case by case basis.

Comparing huge binary files is not its typical strength, though.

</disagree>

[Sob]

You can try my "multicore killer". :) It first computes one or more (configurable) of seven types of hashes for first file, then it does it for second file and compares the results. I wrote it when I was playing with threads programming and wanted to create something at least a little useful. So it might not be completely polished, but it works fine.

Suggested button parameters for TC: %P%S2 %T%R1

http://web.hisoftware.cz/sob/download/ChkFiles1.7z (32 and 64-bit binaries and VC2008 source)

[Hacker]

Sob,
Thank you, too, will try!

Roman

[ehab]

i tried 2Gb file size and it works fine. using HxD i was surprised to see it didn't show the difference with small text file having unicode characters, however it did report that size if different. Thanks for the HxD suggestion

[Hacker]

If anyone is interested, I have now created a Simple file compare using AutoHotkey. It first checks the file sizes, then reads data at specific points in the files and if it still does not find a difference, calculates the MD5 of the compared files.

Roman