Retaining Bash history from all sessions

I've noticed that when I have many sessions open, the history from one closed session will overwrite the history from another earlier closed session so that when I open a new session I only see the history of the most recently closed session.

Is there a way I can merge/retain all Bash history from all sessions?

I was thinking about something in the .bash_logout, perhaps a func to merge the histories, appending only the new lines to the history file, but the problem is that the history numbering overlaps, so this could be tricky.

Another question would be how Bash handles the history, is it before or after the processing of the history file? If it's after, then would bash just overwrite the history file with the current session history regardless of what is in .bash_logout?

Any Ideas?

http://www.ducea.com/2006/05/15/linu...-bash_history/

note that I am a fan of having zero history on reboot I touch a new file to stop intruders reading certain things

yes I tried this no history for a while too but the inconvenience outweighs the small security I think.

thanks for the link, looked too basic to start, but they mention history -a which I have found elsewhere as a possible solution...

open a shell command
info bash

has more juicy stuff

Here's the history relevant part from my ~/.bashrc

# handle history file gracefully for multiple windows open
shopt -s histappend
export PROMPT_COMMAND='history -a'
# 'normal' history stuff
export HISTFILESIZE=6000
export HISTSIZE=2000
export HISTTIMEFORMAT="%F %T "
export HISTCONTROL=ignoreboth
# and things I don't want to see in my history (ever)
export HISTIGNORE="*PROMPT*:lsc:cd:cd ..:pwd:exit:mc:clear:history *:cd \"\`echo *:ps -A:top:./configure --help:locate:fj"

Cheers,
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