##How to check file integrity with shasum
For verifying the integrity (but not authenticity of data, i.e., who authored it or the origin of the file) of a file, it is necessary to run a checksum function on the file which will output a value and compare it to a previously stored checksum value; if it matches we can be relatively confident that the file hasn't been tampered with or altered.
You might be asked to verify a file's sha1sum or sha2sum–all this means is calculating and verifying the cryptographic sha1 or sha2 hash value or digest included in the file.
###Various commands and methods for verifying shasum 1 or 2:
Organic:
In terminal run:
For sha2:
shasum -a 256 filename/path
For sha1:
shasum -a 1 filename/path
Use your eyeballs and compare by sight the expected hash and the computed hash in the terminal. Eye strain might ensue.
Artisanal & organic:
Run the above commands. Copy the resulting shasum with Ctrl + C.
In browser or file use Ctrl + F with your copied shasum; if you find a match, congrats your file is fine! If no match, your file might have been altered or tampered with.
Inorganic, man-made:
Use shasum check command. Runs diff and prints results in terminal.
In terminal run:
echo 'your_expected_shasum_here_followed_by_a_space *name_of_file_to_check_after_asterisk' | shasum -c