How to verify sha256sum without a SHASUMS file on command line

gistfile1.md

To verify a shasum or any other integrity hash, from a website that hosts a file with its shasum, you would normally take the following approach:

1. Download the file and its SHASUMS file and place both of these files in the same directory
2. run sha256sum -c SHASUMS

If the file integrity is intact then it would output:

filename: OK

But what if you only have the file and the shasum and no file? Case in point: Downloading boost libraries from official website

You could do a step before step 1 by creating a properly formatted SHASUM file, using the SHASUM taken from the website and the file name.

But a faster and easier way is by using pipes and running shasum using standard input

echo "$ACTUAL_SHA_VALUE  $FILENAME" | sha256sum -c

where $ACTUAL_SHA_VALUE is the shasum copied from the site and $FILENAME is the file name.

NOTE: There are two (2) spaces in between $ACTUAL_SHA_VALUE and $FILENAME. If this is not the case you will get an error of not having properly formatted SHA256 checksum lines