PLaying with some open source project I had the need to verify a SHA 256 digest and the Makefile of a project I was reading was using sha256sum. This is not available on OSX...
Couple of solutions then:
1. Use openssl (especially if you installed a newer version through 'brew'):
'openssl dgst -sha256 <filename>'
2. Use 'shasum -a 256 <filename>' in place of 'sha256sum <filename'