Freebsd .bash history hardering hack

# chflags sappnd,sunlnk .bash_history
# rm -rf .bash_history
rm: .bash_history: Operation not permitted

.bashrc

shopt -s histappend
readonly PROMPT_COMMAND="history -a"

readonly HISTFILE
readonly HISTFILESIZE
readonly HISTSIZE
readonly HISTCMD
readonly HISTCONTROL
readonly HISTIGNORE