将 tcpdump 保存为变量答案

【问题标题】：saving tcpdump as variable将 tcpdump 保存为变量
【发布时间】：2020-12-15 07:34:10
【问题描述】：

我正在尝试从 tcpdump 读取数据，但没有得到正确的输出

import socket
import colorama
import time
import os
import csv
from datetime import datetime

colorama.init()
BLUE = colorama.Fore.BLUE
GRAY = colorama.Fore.LIGHTBLACK_EX
RED = colorama.Fore.RED
GREEN = colorama.Fore.GREEN
YELLOW = colorama.Fore.YELLOW
RESET = colorama.Fore.RESET

def preservation():
    def data():
        data = os.system('tcpdump -i en0 -z 192.168.0.1 -c 10')
        return data
    signal = str(data())
    print(f'{RED}{signal}{RESET}')
    while True:
        if 'seavers-mbp' in signal:
            now = datetime.now()
            print(f'{RED}***PACKET FOUND***{RESET}')
            print("now =", now)
            dt_string = now.strftime("%d/%m/%Y %H:%M:%S")
            caught = [(dt_string), (signal)]
            with open('watchdog.csv' 'a') as file:
                file_writer = csv.writer(file)
                file_writer.writerow(caught)
        print(f'{BLUE}cycle complete{RESET}')
        time.sleep(.5)
        signal = str(data())


preservation()

信号以0 的形式返回，而不是实际的 tcpdump 我是否必须将其保存到 pcap 文件并读取该文件，或者是否可以将输出保存为变量

（顺便说一句，我以超级用户身份运行此脚本）

【问题讨论】：

标签： python tcpdump

【解决方案1】：

os.system(command) 确实返回命令的退出代码而不是输出。

文档状态 (https://docs.python.org/3/library/os.html#os.system)：

Execute the command (a string) in a subshell. This is implemented by calling the Standard C function system(), and has the same limitations. Changes to sys.stdin, etc. are not reflected in the environment of the executed command. If command generates any output, it will be sent to the interpreter standard output stream.

因此您需要将输出重定向到文件或使用subprocess 模块来获取调用stdout

【讨论】：