here is a script.

import sys

def summarize(path):
    total = 0
    errors = 0
    for line in open(path):
        total += 1
        if "ERROR" in line:
            errors += 1
    print(f"lines {total} errors {errors}")

summarize(sys.argv[1])

add a --json flag that prints the same two numbers as json instead. return the whole script.