#!/usr/bin/env bash

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

prefix=splitted
suffix=.log

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