import selectimport osimport subprocessimport timeimport fcntlargs = [‘python‘,‘./fetch_file2.py‘,ip,path]proc = subprocess.Popen(args, stdout=subprocess.PIPE,stderr=subprocess.PIPE,close_fds=True)def non_block_read(output):  # 避免阻塞    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 ""while proc.poll() is None: #fetch中rsync结束。但是fetch没有结束(怀疑输出过大)  导致这里一直是None    pass                                                print proc.poll()  # 杀死fetch进程  返回-9print proc.stderr.read() #阻塞
#方法1：#non_block_read(proc.stderr) #防止阻塞
#方法2：select_rfds = [ proc.stdout, proc.stderr](rfds, wfds, efds) = select.select(select_rfds, [],[])if proc.stderr in rfds:          #不存在。若select_rfds=[stderr],则阻塞在select上    len = proc.stderr.read(10)    if len == 0:        print "empty"else:    print "proc.stderr"if proc.stdout in rfds:     print "proc.stdout"