#!/bin/bash


LOGFILE=log.log
RETAIN_NUM_LINES=10

function logsetup {
    TMP=$(tail -n $RETAIN_NUM_LINES $LOGFILE 2>/dev/null) && echo "${TMP}" > $LOGFILE
    exec > >(tee -a $LOGFILE)
    exec 2>&1
}

function log {
    echo "[$(date --rfc-3339=seconds)]: $*"
}

logsetup
log hello this is a log