#!/usr/bin/env bash

#default interval: 60 sec
declare -i interval=${1:-60}

prefix=splitted
suffix=.log

declare -i till n=0
declare file line
while true; do
    n+=1
    printf -v file "${prefix}_%04d${suffix}" $n
    #echo "> $file" >&2
    till=$(($SECONDS + $interval))
    while read -r line; do
        [ $till -gt $SECONDS ] && continue 2
        echo "$line"
    done > "$file"
    break
done