[Help-bash] `shopt -s histappend` vs `export PROMPT_COMMAND="history -a"`

[Peng Yu]

Hi,

I see the following two ways to update the history file. Are they
equivalent? Or they might be slightly different in some way?

- `shopt -s histappend`
- `export PROMPT_COMMAND="history -a"`

I have `shopt -s histappend` in ~/.bashrc in a machine whose home is
on an nfs. But I frequently encounter hanging on history related
commands upon long. (I have not got the time to try export
PROMPT_COMMAND="history -a"`).

Could `shopt -s histappend` cause NFS related problems?

-- 
Regards,
Peng