List up chapter markers.

MarkerList.sh

#!/usr/bin/env zsh

for difffile in *.txt
do
    hms=`sort -n $difffile | awk 'BEGIN{threshold = 1000} $1 < threshold {print $2}' | sort -n | head -n 1 | ruby sec_to_hms.rb`
    if [[ $hms == "00:00:00" ]] then
        hms=`sort -n $difffile | awk '{print $2}' | head -n 1 | ruby sec_to_hms.rb`
    fi
    echo "$hms ${difffile}"
done