emscripten/tests/unistd/dup.out

DUP
errno: 0
f: 1
f2,f3: 1
close(f1): 0
close(f2): 0
close(f3): 0

DUP2
errno: 0
f: 1
f2,f3: 1
close(f1): 0
close(f2): 0
close(f3): -1