How can I remove duplicates in my .bash_history, preserving order?

I really enjoying using control+r to recursively search my command history. I've found a few good options I like to use with it: # ignore duplicate commands, ignore commands starting with a space export HISTCONTROL=erasedups:ignorespace # keep the last 5000 entries export HISTSIZE=5000 # append to the history instead of overwriting (good for multiple connections) shopt -s histappend The only problem for me is that erasedups only erases sequential duplicates - so that with this string of commands: ls cd ~ ls The ls command will actually be recorded twice. I've thought about periodically running w/ cron: cat .bash_history | sort | uniq > temp.txt mv temp.txt .bash_history This would achieve removing the duplicates, but unfortunately the order would not be preserved. If I don't sort the file first I don't believe uniq can work properly. How can I remove duplicates in my .bash_history, preserving order? ### Extra Credit: Are there any problems with overwriting the .bash_history file via a script? For example, if you remove an apache log file I think you need to send a nohup / reset signal with kill to have it flush it's connection to the file. If that is the case with the .bash_history file, perhaps I could somehow use ps to check and make sure there are no connected sessions before the filtering script is run?