管道输出subprocess.Popen到文件

Question

我需要使用subprocess.Popen启动一些长时间运行的进程，并希望从每个自动管道传输stdout和stderr以分离日志文件。每个进程将同时运行几分钟，并且我希望在进程运行时将每个进程写入两个日志文件（stdout和stderr）。

我是否需要在循环中的每个进程上不断调用p.communicate()以更新每个日志文件，或者是否有某种方法来调用原始的Popen命令以便stdout和stderr自动流式传输以打开文件句柄？

Answer 1

对于the docs，

stdin，stdout和stderr分别指定执行程序的标准输入，标准输出和标准错误文件句柄。有效值为PIPE，现有文件描述符（正整数），现有文件对象和无。

所以只需将open-for-writing文件对象作为命名参数stdout=和stderr=传递，你应该没问题！

Answer 2

你可以将stdout和stderr作为参数传递给Popen()

subprocess.Popen(self, args, bufsize=0, executable=None, stdin=None, stdout=None,
                 stderr=None, preexec_fn=None, close_fds=False, shell=False,
                 cwd=None, env=None, universal_newlines=False, startupinfo=None, 
                 creationflags=0)

例如

>>> import subprocess
>>> with open("stdout.txt","wb") as out, open("stderr.txt","wb") as err:
...    subprocess.Popen("ls",stdout=out,stderr=err)
... 
<subprocess.Popen object at 0xa3519ec>
>>> 

Answer 3

我同时运行两个子进程，并将两者的输出保存到一个日志文件中。我还建立了一个超时来处理挂起的子进程。当输出太大时，超时总是触发，并且任何一个子进程的stdout都不会保存到日志文件中。亚历克斯上面提出的答案并没有解决它。

# Currently open log file.
log = None

# If we send stdout to subprocess.PIPE, the tests with lots of output fill up the pipe and
# make the script hang. So, write the subprocess's stdout directly to the log file.
def run(cmd, logfile):
   #print os.getcwd()
   #print ("Running test: %s" % cmd)
   global log
   p = subprocess.Popen(cmd, shell=True, universal_newlines = True, stderr=subprocess.STDOUT, stdout=logfile)
   log = logfile
   return p


# To make a subprocess capable of timing out
class Alarm(Exception):
   pass

def alarm_handler(signum, frame):
   log.flush()
   raise Alarm


####
## This function runs a given command with the given flags, and records the
## results in a log file. 
####
def runTest(cmd_path, flags, name):

  log = open(name, 'w')

  print >> log, "header"
  log.flush()

  cmd1_ret = run(cmd_path + "command1 " + flags, log)
  log.flush()
  cmd2_ret = run(cmd_path + "command2", log)
  #log.flush()
  sys.stdout.flush()

  start_timer = time.time()  # time how long this took to finish

  signal.signal(signal.SIGALRM, alarm_handler)
  signal.alarm(5)  #seconds

  try:
    cmd1_ret.communicate()

  except Alarm:
    print "myScript.py: Oops, taking too long!"
    kill_string = ("kill -9 %d" % cmd1_ret.pid)
    os.system(kill_string)
    kill_string = ("kill -9 %d" % cmd2_ret.pid)
    os.system(kill_string)
    #sys.exit()

  end_timer = time.time()
  print >> log, "closing message"

  log.close()