#!/usr/bin/env python
# Exercise 12f
# tail command

import sys
import argparse
from pathlib import Path

parser = argparse.ArgumentParser()
parser.add_argument("stream", default=sys.stdin, nargs="*")
parser.add_argument("-v", "--verbose", action="store_true")
parser.add_argument("-n", "--lines", default="10", type=str)
args = parser.parse_args()
res = []


def intonum(n):
    try:
        return abs(int(n))
    except ValueError:
        print(f"tail: el número de líneas no es válido: «{n}»")
        sys.exit(1)


def getlines(lines, n):
    lines = list(map(lambda l: l.rstrip(), lines))
    num = intonum(n)
    if n[0] == "+":
        return lines[num-1:]
    return lines[-num:]


if isinstance(args.stream, list):
    for path in args.stream:
        lines = Path(path).open().readlines()
        header = [""] if len(res) != 0 else []
        if args.verbose:
            header += [f"==> {path} <=="]
        res += header + getlines(lines, args.lines)
else:
    lines = args.stream.readlines()
    header = ["==> entrada estándar <=="] if args.verbose else []
    res += header + getlines(lines, args.lines)

print("\n".join(res))