当子进程引发CalledProcessError异常时,检查命令的返回码

Question

我想stdout在python(3)脚本中捕获shell命令的流,并且能够同时检查shell命令的返回代码,如果它返回错误(即,如果它的返回代码是不是0).

subprocess.check_output似乎是这样做的合适方法.来自subprocess的手册页:

check_output(*popenargs, **kwargs)
    Run command with arguments and return its output as a byte string.

    If the exit code was non-zero it raises a CalledProcessError.  The
    CalledProcessError object will have the return code in the returncode
    attribute and output in the output attribute.

但是,当它失败时,我没有成功从shell命令获取返回码.我的代码看起来像这样:

import subprocess
failing_command=['ls', 'non_existent_dir']

try:
    subprocess.check_output(failing_command)
except:
    ret = subprocess.CalledProcessError.returncode  # <- this seems to be wrong
    if ret in (1, 2):
        print("the command failed")
    elif ret in (3, 4, 5):
        print("the command failed very much")

此代码在处理异常本身时引发异常:

Traceback (most recent call last):
  File "<stdin>", line 4, in <module>
AttributeError: type object 'CalledProcessError' has no attribute 'returncode'

我承认我不知道我哪里错了.

Answer 1

要获取进程输出和返回的代码:

from subprocess import Popen, PIPE

p = Popen(["ls", "non existent"], stdout=PIPE)
output = p.communicate()[0]
print(p.returncode)

subprocess.CalledProcessError是一个班级.要访问returncode使用异常实例:

from subprocess import CalledProcessError, check_output

try:
    output = check_output(["ls", "non existent"])
    returncode = 0
except CalledProcessError as e:
    output = e.output
    returncode = e.returncode

print(returncode)

Answer 2

很可能我的答案不再相关，但我认为可以通过以下代码解决：

import subprocess
failing_command='ls non_existent_dir'

try:
    subprocess.check_output(failing_command, shell=True, stderr=subprocess.STDOUT)
except subprocess.CalledProcessError as e:
    ret =   e.returncode 
    if ret in (1, 2):
        print("the command failed")
    elif ret in (3, 4, 5):
        print("the command failed very much")