st_size: 6

ftruncate(10): 0
errno: 0
st_size: 10

ftruncate(4): 0
errno: 0
st_size: 4

ftruncate(-1): -1
errno: 22
st_size: 4

truncate(2): 0
errno: 0
st_size: 2

truncate(readonly, 2): -1
errno: 13
st_size: 6

ftruncate(readonly, 4): -1
errno: 22
st_size: 6