如何在后台运行tshark命令并使用python中的子进程退出它

Question

我想使用tsharkWireshark的命令行风格进行数据包捕获,同时连接到telnet上的远程主机设备.我想调用我为捕获编写的函数:

def wire_cap(ip1,ip2,op_fold,file_name,duration):  # invoke tshark to capture traffic during session
    if duration == 0:
        cmd='"tshark" -i 1 -P -w '+ op_fold+file_name+'.pcap src ' + str(ip1) + ' or src '+ str(ip2)
    else:
        cmd='"tshark" -i 1 -a duration:'+str(duration)+' -P -w '+ op_fold+file_name+'.pcap src ' + str(ip1) + ' or src '+ str(ip2)

    p = subprocess.Popen(cmd, shell=True,stderr=subprocess.PIPE)
    while True:
        out = p.stderr.read(1)
        if out == '' and p.poll() != None:
            break
        if out != '':
            sys.stdout.write(out)
            sys.stdout.flush()

出于调试目的,我想在后台运行此函数,并在需要时调用它,并在我获取捕获时停止它.就像是:

Start a thread or a background process called wire_capture
//Do something here
Stop the thread or the background process wire_capture

通过阅读一点,我意识到thread.start_new_thread()并且threading.Thread()似乎只有在我知道捕获的持续时间(退出条件)时才适合.我尝试使用,thread.exit()但它的行为就像sys.exit()完全停止了程序的执行.我也试过threading.Event()如下:

if cap_flg:
    print "Starting a packet capture thread...."
    th_capture = threading.Thread(target=wire_cap, name='Thread_Packet_Capture', args=(IP1, IP2, output, 'wire_capture', 0, ))
    th_capture.setDaemon(True)
    th_capture.start()

.
.
.
.
.

if cap_flg:
    thread_kill = threading.Event()
    print "Exiting the packet capture thread...."
    thread_kill.set()
    th_capture.join()

我想知道当我想停止它时如何使进程停止(就像可以添加的退出条件,以便我可以退出线程执行).我试过的上面的代码似乎不起作用.

Answer 1

该threading.Event()方法是正确的，但是您需要该事件在两个线程中都可见，因此您需要在启动第二个线程并将其传入之前创建它：

if cap_flg:
    print "Starting a packet capture thread...."
    thread_kill = threading.Event()
    th_capture = threading.Thread(target=wire_cap, name='Thread_Packet_Capture', args=(IP1, IP2, output, 'wire_capture', 0, thread_kill))
    th_capture.setDaemon(True)
    th_capture.start()

在该while循环中，让监视线程在每次迭代时检查事件，tshark如果设置了该事件，则停止循环（也可能杀死它启动的事件）。您还需要确保进程不会永远等待进程的输出，并忽略终止事件，仅在有可用数据时才从管道中读取：

def wire_cap(ip1,ip2,op_fold,file_name,duration,event):  # invoke tshark to capture traffic during session
    if duration == 0:
        cmd='"tshark" -i 1 -P -w '+ op_fold+file_name+'.pcap src ' + str(ip1) + ' or src '+ str(ip2)
    else:
        cmd='"tshark" -i 1 -a duration:'+str(duration)+' -P -w '+ op_fold+file_name+'.pcap src ' + str(ip1) + ' or src '+ str(ip2)

    p = subprocess.Popen(cmd, shell=True,stderr=subprocess.PIPE)
    while not event.is_set():
        # Make sure to not block forever waiting for 
        # the process to say things, so we can see if
        # the event gets set. Only read if data is available.
        if len(select.select([p.stderr], [], [], 0.1)) > 0:
            out = p.stderr.read(1)
            if out == '' and p.poll() != None:
                break
            if out != '':
                sys.stdout.write(out)
                sys.stdout.flush()
    p.kill()

然后要实际告诉线程停止，您只需设置事件：

if cap_flg:
    print "Exiting the packet capture thread...."
    thread_kill.set()
    th_capture.join()