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I need to create a list of checksums of the files that are inside a directory, including any subdirectories.

The command that I try to execute is the following:

 sha256sum -b * 

Usage:


 -b = Read in Binary.

 * = Specifies that you must verify all file extensions.

With the command I get the following output:

sha256sum: test0: Is a directory e3d748fdf10adca15c96d77a38aa0447fa87af9c297cb0b75e314cc313367daf *test1.txt db0c7a354881fe2dd1b45642a68f6a971c7421e8fdffe56ffa7c740111e07274 *test2.txt

Instead of reporting that test0 is a directory, you should also generate the checksum of the content.

Do you recommend always using -b in any type of file? In what cases should -t be used?

Is it possible to filter the types of files I want to omit in the verification, without having to add all the files I want to admit? What command should I execute?

I looked for help but I do not find anything related.

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You can use find to find all files in the directory tree, and let it run sha256sum. The following command line will create checksums for the files in the current directory and its subdirectories.

find . -type f -exec sha256sum {} \;

I don't use the options -b and -t, but if you wish, you can use -b for all files. The only difference that I notice is the asterisk in front of each file name.

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  • Excellent! And why should we add find instead of containing the option within the same sha256sum program? Does this usually happen? – MarianoM Nov 9 '18 at 8:48
  • Now I do not understand the use of the curly braces {} well. I was reading a bit more but I found that "it can be used as a placeholder for each file that locates the search command" what does that mean? Does it refer to the coloring of the text or some other reason? I tried inserting a route / test and accepted it. This confuses me even more. It's just a curiosity to learn more about the parameters used. – MarianoM Nov 9 '18 at 8:52
  • Using find is a good way to find files in subdirectories, and with the -exec option it is possible to run commands with parameters {}. Each file found by find will be replacing the spaceholder {}, so in your case sha256sum will work on each of the files one after another. – sudodus Nov 9 '18 at 8:53
  • Thank you so much for everything. As a clarification, due to tests that I was doing, if this command is going to be used; you should not use the -b option if you do not want to have to edit the text later because when you run (sha256sum -c) you can not find the path of the files. However, I wonder if there will be a difference between using -b or not. – MarianoM Nov 9 '18 at 12:01
  • I think the asterisk (*) in the output is the only difference. Maybe (I am guessing here) long ago there was some difference (that some characters in binary files could create problems like truncation of the process). – sudodus Nov 9 '18 at 14:34
2

TL;DR

cd /path/to/working/directory
sha256sum <(find . -type f -exec sha256sum \; | sort)

Intro

A more complete answer to the one above, which fixes the problem with find "finding" files in different orders on different systems.

Piping output to file, compare with diff

Firstly, you probably want to pipe the output to a file for comparison with diff. For this you would use

find . -type f -exec sha256sum {} \; > file1.lst

Then on your other system

find . -type f -exec sha256sum {} \; > file2.lst
rsync file2.lst user@host:/home/user/file2.lst
ssh user@host
diff file1.lst file2.lst # might not match due to order

Fixing order of files found with find by piping to sort

Here I am assuming you are doing something similar to what I required this for - copying files from one system to another over a network and verifying the integrity of those files.

What I found was that the order in which find finds files can vary between two systems, even when the OS is "Debian" in both cases.

Therefore, one needs to sort the output in the text files.

sort file1.lst > file1sorted.lst
sort file2.lst > file2sorted.lst
diff file1.lst file2.lst # bad
diff file1sorted.lst file2sorted.lst # ok

You can do the find and sort all in one line, while redirecting the output to a file.

find . -type f -exec sha256sum {} \; | sort > file1.lst

Other sha/md5 sums

You might want to have an increased level of shasumming. To use the 512 bit version simply do;

find . -type f -exec sha512sum {} \; | sort > file1.lst

Alternatively, 256 bit might be overkill for what you are doing, so do

find . -type f -exec md5sum {} \; | sort > file1.lst

A complete 1 line command to compare 2 directories with 1 shasum output

Now, if you have many files and do not want to save the output to a file, you could simply shasum the output. To do this, use

sha256sum <(find . -type -f -exec sha256sum \; | sort)

The pipe to sort is required to ensure the output is sorted before computing the final sha256sum. Without this, if find finds files in a different order, despite the shasums for each file being correct, the overall shasum will depend on the order.

Problem relating to diff output and paths used

You may have some path which looks like

/A/B/C/*

where * are the subdirectories and files you are interested in shasumming. If A/B/C are 1 or more directories containing only 1 subfolder you might end up accidentally running your shasum command in the wrong directory, resulting in the following

sort1.txt
sha256sum1    ./A/B/C/file1

sort2.txt
sha256sum2    ./B/C/file1

Even if sha256sum = sha256sum2 diff will say the files are different. (Because they are due to the different base directory in the path.)

Here is a short python3 code to check the sums line by line, which solves this problem.

#!/usr/bin/env python3
file1_name = "sort1.txt"
file2_name = "sort2.txt"
file1 = open(file1_name, 'r')
file2 = open(file2_name, 'r')
file1_lines = file1.readlines();
file2_lines = file2.readlines();
if(len(file1_lines) == len(file2_lines)):
    print("line numbers ok")
    for i in range(len(file1_lines)):
        line1 = file1_lines[i]
        line2 = file2_lines[i]
        line1_split = line1.split(' ')
        line2_split = line2.split(' ')
        shasum1 = line1_split[0]
        shasum2 = line2_split[0]
        if(shasum1 != shasum2):
            print("shasum error: ", line1)
else:
    print("Error: file ", file1_name, " number of lines != ", file2_name, " number of lines")
print("done")

I initially wanted to write a shell script to do this, but I got bored trying to figure out how to do it, so went back to python.

This makes me think that actually writing a python code to do the entire thing would have been easier, except for the find command.

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  • 1
    +1: I see what you mean. Sorting helps, when find finds files in different order. – sudodus Sep 4 '20 at 10:55
  • 1
    @sudodus It's possible this is only relevant when doing this across different systems - on the same machine presumably the same results occur in different copies of the same directory contents. (aka: presumably find behaves consistently) – user3728501 Sep 4 '20 at 12:51
  • When doing this, usually between windows and linux, I use get-filehash *.* in powershell, and find . -type f -exec sha256sum {} \; in bash. I just copy the output of both to new files in notepad++, uppercase everything, and replace everything from the end of the hash to the start of the filename with \t, then run a csv plugin to SELECT * FROM THIS ORDER BY Col2 and then dump that back into the file, then run compare, which when it's a good copy tells me the files match, then closes them and I'm done. That being said I don't have to do this often enough to warrant an actual script. – gattsbr Jan 17 at 17:13
  • good comment about sorting to accepted question, but your TL;DR makes one integral sum, not list of sums for each file. That IMHO should be mentioned there. Sorting by file name, not shasum would be practical for many IMHO, I could not write one-liner right away now... – Martian2020 Feb 13 at 6:53
1

Late answer, but for the sake of documentation...

The other answers suggest to call sha256sum via find and the -exec option. This has the effect that sha256sum is called once for each file, which is a significant overhead for the OS starting processes.

A more efficient solution is to convert the find results to command line arguments by piping it through xargs and call sha256sum that way. xargs runs sha256sum once or in large badges if there are too many lines.

find /path/to/your/dir -type f | xargs sha256sum -b

In case that you have filenames with whitespaces, use the -print0 flag in find and -0 flag in xargs to terminate strings with \0

find /path/to/your/dir -type f -print0 | xargs -0 sha256sum -b

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