bash history protection

# only append to history
shopt -s histappend
# keep one meelion lines in memory
export HISTSIZE=1000000
# and in the file
export HISTFILESIZE=$HISTSIZE
# prevent shell instances that don't have these set from clobbering the real history
export HISTFILE=~/.bash_history_safe
# timestamps are nice
export HISTTIMEFORMAT='%F %T '