# 源码

def run(*popenargs, input=None, capture_output=False, timeout=None, check=False, **kwargs):
  if input is not None:
    if 'stdin' in kwargs:
      raise ValueError('stdin and input arguments may not both be used.')
    kwargs['stdin'] = PIPE
  
  if capture_output:
    if ('stdout' in kwargs) or ('stderr' in kwargs):
      raise ValueError('stdout and stderr arguments may not be used '
               'with capture_output.')
    kwargs['stdout'] = PIPE
    kwargs['stderr'] = PIPE
  
  with Popen(*popenargs, **kwargs) as process:
    try:
      stdout, stderr = process.communicate(input, timeout=timeout)
    except TimeoutExpired:
      process.kill()
      stdout, stderr = process.communicate()
      raise TimeoutExpired(process.args, timeout, output=stdout,
                 stderr=stderr)
    except: # Including KeyboardInterrupt, communicate handled that.
      process.kill()
      # We don't call process.wait() as .__exit__ does that for us.
      raise
    retcode = process.poll()
    if check and retcode:
      raise CalledProcessError(retcode, process.args,
                   output=stdout, stderr=stderr)
  return CompletedProcess(process.args, retcode, stdout, stderr)

# 源码
def call(*popenargs, timeout=None, **kwargs):
  with Popen(*popenargs, **kwargs) as p:
    try:
      return p.wait(timeout=timeout)
    except:
      p.kill()
      p.wait()
      raise

# 源码
def check_call(*popenargs, **kwargs):
  retcode = call(*popenargs, **kwargs)
  if retcode:
    cmd = kwargs.get("args")
    if cmd is None:
      cmd = popenargs[0]
    raise CalledProcessError(retcode, cmd)
  return 0

# 源码

def check_output(*popenargs, timeout=None, **kwargs):
  if 'stdout' in kwargs:
    raise ValueError('stdout argument not allowed, it will be overridden.')

  if 'input' in kwargs and kwargs['input'] is None:
    # Explicitly passing input=None was previously equivalent to passing an
    # empty string. That is maintained here for backwards compatibility.
    kwargs['input'] = '' if kwargs.get('universal_newlines', False) else b''

  return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
        **kwargs).stdout

# 源码
try:
  data = check_output(cmd, shell=True, universal_newlines=True, stderr=STDOUT)
  exitcode = 0
except CalledProcessError as ex:
  data = ex.output
  exitcode = ex.returncode
if data[-1:] == '\n':
  data = data[:-1]
return exitcode, data