# History setup
    export      HISTSIZE=50000
    export      HISTFILE=~/.bash_history
    export      HISTFILESIZE=50000
    export      HISTIGNORE="?:??:td[ud]:fg *:exit:logout"
#   export      HISTCONTROL=ignoredups


    declare -i  HIST_KEEP_BATCH=50
    declare -i  HIST_KEEP_INTERVAL=3600

    declare -i  LAST_HSYNC_TIME=0
                PROMPT_COMMAND=hsave

    hsync() {
        history -a
        LAST_HSYNC_TIME=$SECONDS
    }

    hsave() {
        # Command-count-based
    #   if [ $(( $HISTCMD % $HIST_KEEP_BATCH )) -eq 0 ]; then
    #       hsync
    #   fi

        # Time-interval-based:
    #   if [ $(( $SECONDS - $LAST_HSYNC_TIME > $HIST_KEEP_INTERVAL )) ]; then
    #       hsync
    #   fi

        # Every time:
        hsync
    }