Bash delete_last_n_histories function

delete_last_n_histories.sh

# Delete the last n (default 1) histories from .bash_history and the history command cache
delete_last_n_histories() {
    local count last HISTTIMEFORMAT regex temp
 
    count=$((${1:-1} + 1))
    last=$(($HISTCMD - $count))
    echo "Deleting the following commands from .bash_history:"; history $count
    HISTTIMEFORMAT="##%s###### "
 
    # Contruct regex to find commands in .bash_history based on timestamp
    # (NOTE: Change $(history $count) to $(history $(($count + 1))) if `history -a` is in $PROMPT_COMMAND)
    while read line; do temp="${line#*#}"; regex="${temp%%##*}|$regex"; done <<< "$(history $count)"
 
    # Omit selected histories from .bash_history
    awk '/^('"${regex%|}"')$/ { del_mode = 1; next }
        /^#[0-9]{1,11}$/ { del_mode = 0 } !del_mode { print }
    ' "$HOME/.bash_history" >| "$HOME/.history_delete_tmp" && mv "$HOME/.history_delete_tmp" "$HOME/.bash_history"
 
    # Delete from cached history
    for (( i=$(($HISTCMD)); i >= $last; i--)); do
        history -d $i
    done
}