How to check SHA-256 checksum on files?

Question

I know that you can use shasum -a 256 filename to create a SHA-256 checksum for a file, but how can one automate the check if known SHA-256 matches a file on a mac?

Since the Mac shell is zsh by default, but our CI runner uses bash, I want to know both versions (for local testing and for the ci).

Answer 1

I figured it out!

Using the awk '{ print $1 }', you can omit the filename printed by shasum. This way you can write an easy if statement to check if the SHA checksums match.

zsh version

sha=$( shasum -a 256 filename | awk '{ print $1 }')
if [[ $sha == "known checksum" ]] {
  echo "sha matches"
} else {
  echo $sha "does not match the required: known checksum"
}

bash version

sha=$( shasum -a 256 filename | awk '{ print $1 }')
if [[ $sha == "known checksum" ]]
then
  echo "sha matches"
else
  echo $sha "does not match the required: known checksum"
fi