python逐行读取子进程的输出代码，python逐行输出代码,python中默认情况下

python逐行读取子进程的输出代码，python逐行输出代码,python中默认情况下

python中默认情况下是等待子进程完成之后，一下读取子进程的输出，要想逐行读取，需要自己做一点小技巧。

import sys,os,socketimport datetimeimport fcntlimport subprocessfrom threading import Threaddef log_worker(stdout):    ''' needs to be in a thread so we can read the stdout w/o blocking '''    username, hostname = os.environ.get('USER'), socket.gethostname()    log_file = '/var/log/mysql-%s.log' % username    log = open(log_file, 'a')    while True:        output = non_block_read(stdout).strip()        if output:            ''' [Tue Oct 30 22:13:13 2012 cseibert@host1]> '''            prompt = '[%(timestamp)s %(username)s@%(host)s]> \n' % dict(                    timestamp=datetime.datetime.now().strftime('%a %b %d %H:%M:%S %Y'),                    username=username,                    host=hostname)            print prompt + output            log.write(prompt + output + '\n')    log.close()def non_block_read(output):    ''' even in a thread, a normal read with block until the buffer is full '''    fd = output.fileno()    fl = fcntl.fcntl(fd, fcntl.F_GETFL)    fcntl.fcntl(fd, fcntl.F_SETFL, fl | os.O_NONBLOCK)    try:        return output.read()    except:        return ''if __name__ == '__main__':    sub_process = subprocess.Popen(        ['sh', '/root/test/dummy.sh'],        stdin=sys.stdin,        stdout=subprocess.PIPE,        stderr=subprocess.PIPE)    thread = Thread(target=log_worker, args=[sub_process.stdout])    thread.daemon = True    thread.start()    sub_process.wait()    thread.join(timeout=1)