import os

with open('in.txt', 'w') as file:
	file.write("Lorem ipsum\n")

# Works and sends 'size' bytes
with open('in.txt', 'r') as infile, open('out.txt', 'w') as outfile:
    size = os.stat('in.txt').st_size
    print(os.sendfile(outfile.fileno(), infile.fileno(), 0, 10000))

# Should return zero and send nothing -> breaks on Solaris
with open('in.txt', 'r') as infile, open('out.txt', 'w') as outfile:
    size = os.stat('in.txt').st_size
    print(os.sendfile(outfile.fileno(), infile.fileno(), size, 10000))