openssl based sha256 checksum utility works on macOS

sha256

#!/usr/bin/env /bin/bash

# SHA 256 based on openssl
# 
# sha256 similar to the classic "md5sum" command line
#

if [[ ${#} -gt 0 ]]
then
    # iterate over all arguments
    while [[ ${#} -gt 0 ]]
    do
        if [[ -f $1 ]]
        then
            openssl dgst -sha256 "$1" | awk '{print $NF}' -
        else
            echo "$1 does not exist."
        fi
    shift
    done
else
    echo $0 files...
fi