relative-times

#!/usr/bin/env python3
# Convert the timestamps in a logfile to relative
import sys
import fileinput

def main():
    first_time = None
    for line in fileinput.input():
        time_sep_idx = line.find(': ')
        num = line[:time_sep_idx]
        content = line[time_sep_idx + 2:]

        if first_time == None:
            first_time = int(num)
            time_offset = 0
        else:
            time_offset = int(num) - first_time
            
        sys.stdout.write("{}: {}".format(time_offset / 1000, content))

main()