'histappend' just makes the shell append its history list (from current session) to the history file, instead of overwriting it. This still occurs at exit time,

'histappend' just makes the shell append its history list (from current session) to the history file, instead of overwriting it. This still occurs at exit time, not immediately. Besides, since you load the HISTFILE at startup, you'll append your whole history (file+session) to the HISTFILE each time you exit a shell, so either it will grow very large quickly, or you set HISTFILESIZE to limit it but as a consequence you'll lose entries (and unfortunately not the oldest). The option "only append the session entries typed in this session", while still using the whole history (file+session) for searching, is missing, as far as I know.