[ls flag] sappnd [chflags flag] sappnd, sappend [Owner-settable] No [OS support] All [Semantics and rationale] Existing data in the file can't be overwritten and the file cannot be truncated [Attribute] 
System append-only
A r c h i v e d
O p a q u e
N o d u m p
S y s t e m a p p e n d - o n l y
S y s t e m i m m u t a b l e
U s e r a p p e n d - o n l y
U s e r i m m u t a b l e
H i d d e n