asciinema rewrite

asciinema_rewrite.sh

#!/bin/bash

# This script rewrites history of an asciinema cast from a starting point in time
# ex: ./asciinema_rewrite.sh in.cast 17.452 3 > out.cast, will remove 3 seconds of each record after 17.452sec

if [[ $# -ne 3 ]]; then
    echo "Invalid number of arguments"
    echo "Usage: $0 filename starting_time remove_time > out.cast"
    exit 2
fi

FILE=$1
START=$2
REMOVE=$3

while IFS= read -r line
do
  if [[ $line =~ ^\[([0-9.]*) ]]; then
    TIME=${BASH_REMATCH[1]}
    if (( $(echo "$TIME >= $START" | bc -l) )); then
      NEWTIME=$(echo "scale=6;${TIME}-${REMOVE}" | bc -l)
      echo "${line/${TIME}/${NEWTIME}}"
    else
      echo "$line"
    fi
  else
    echo "$line"
  fi
done < "$FILE"