How to verify sha256sum for multiple file or one file.

So, lets say you have downloaded the SHA256SUMS files. This file contains the sha256sum for multiple files and you want to compare the values for only one or some of them, then the simplest thing you can do is:

sha256sum -c SHA256SUMS

Now, with this if you do not have some files present then you might get some errors and if you do not want that, then you can try this:

grep <filename> SHA256SUMS|tee /proc/self/fd/2|sha256sum --check -

And now if you have some files under some subdirectories as well and you want to generate the SHA256SUMS file, then the simplest is to use this:

sha256sum $(find . -type f -exec echo {} \+ )
sha256sum $(find . -type f)

Get count of lines in scripts (shell)

If you have tried to get the count of lines in file, the you would know about “nl” or “wc -l”. But as you are aware these give you number of lines with other details as well and you need to post process the number to make sure that you have only number and nothing else. In such cases, it is useful to use the count feature of grep and here is a shorthand to get the count of lines in any shell script:

lines=$(grep -c . <filename>)

shell script for some quick tests on Linux

Head over to the link and grab the script. Just run it and make yourself a little bit more safe 🙂