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Thread: Use md5sum to verify if exist duplicate files

  1. #1
    Join Date
    Apr 2016

    Use md5sum to verify if exist duplicate files


    I need identify many files duplicate on a ubuntu server! For this task I am using the md5sum program! The files are mainly pdf or iso. I need know if the hash get through md5sum software it is the best option to verify if the files it is duplicate, it is the same.
    At the moment I run script with md5sum and I get 500 occurs about files duplicate, with the same hash. Before delete the duplicate files I need know if there is full guarantee that the files are the same!


  2. #2
    Join Date
    Mar 2010
    Lubuntu 14.04 Trusty Tahr

    Re: Use md5sum to verify if exist duplicate files

    Don't use md5sum. There are collisions. Didn't you ask this question today?

    If you are looking for duplicate files on the system, there are tools for that - finddup. Or you can write your own. I did for fun after seeing a /. article about it. I did it in perl.

    * make a list of files and file sizes.
    * group by size, then name
    * if the size of any file is the same, run sha256sum. If they match, then the files are identical. If not, they are different.

    I used temporary files with this data:
    {size}\t{filename}\t{date}\t{full path}
    You can google on why md5sum isn't good enough - and other methods of comparison should be used BEFORE dropping to any hashing. Hashing is expensive. Files of different sizes are not the same, so don't bother.
    Last edited by TheFu; August 26th, 2017 at 03:52 PM.

  3. #3
    Join Date
    Apr 2016

    Re: Use md5sum to verify if exist duplicate files

    Ok, This means which I have three methods to identify which files it is equal:


    After thinking about the subject I decide use the three methods. What do you think about this?
    However I googled about software to identify equal files and I found Fdupes and Jdupes. How many programs do you know to do this task?

    I don't like the finddup. Maybe because I don't know how works with this software ( but I don't like the behaviour when I try discovery the equal files.


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