How do I scp extremely large files

I need to copy extremely large files (30-100G) from a remove server to
a machine where my code will be running. I have code in place now
that uses an sftp connection to scan the file directory watching for
files to show up for me to copy. My question is how do I read in
chunks of these large files and write them out in chunks? I cannot
hold the bytes in memory obviously. Any help or pseudo code is
greatly appreaciated!