通过 python3 子进程发送管道命令

Question

我正在尝试通过 python3.4 执行以下子进程命令

cd /home/mailer-domains/domain | rndc loadkeys domain

我尝试了很多使用 .call 和 .Popen 的方法，但它要么不喜欢我的管道，要么不喜欢我的开关

>>> subprocess.call(['cd /home/mailer-domains/'+domain, '|', 'rndc', 'loadkeys', domain])    
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.4/subprocess.py", line 537, in call
    with Popen(*popenargs, **kwargs) as p:
  File "/usr/local/lib/python3.4/subprocess.py", line 859, in __init__
    restore_signals, start_new_session)
  File "/usr/local/lib/python3.4/subprocess.py", line 1457, in _execute_child
    raise child_exception_type(errno_num, err_msg)
FileNotFoundError: [Errno 2] No such file or directory: 'cd /home/mailer-domains/lecomm.com'

>>> subprocess.call(['cd /home/ex-mailer-domains/'+domain, '&&', 'rndc', 'loadkeys', domain]) 
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.4/subprocess.py", line 537, in call
    with Popen(*popenargs, **kwargs) as p:
  File "/usr/local/lib/python3.4/subprocess.py", line 859, in __init__
    restore_signals, start_new_session)
  File "/usr/local/lib/python3.4/subprocess.py", line 1457, in _execute_child
    raise child_exception_type(errno_num, err_msg)
FileNotFoundError: [Errno 2] No such file or directory: 'cd /home/mailer-domains/lecomm.com'


>>> subprocess.call(['cd', '/home/mailer-domains/'+domain, '&&', 'rndc', 'loadkeys', domain])
cd: too many arguments
2


>>> subprocess.Popen(['cd', '/home/mailer-domains/'+domain, '&&', 'rndc', 'loadkeys', domain])    
<subprocess.Popen object at 0x805aa5860>
cd: too many arguments


>>> subprocess.call(['cd', '/home/mailer-domains/'+domain] '&&' ['rndc', 'loadkeys', domain])    
  File "<stdin>", line 1
    subprocess.call(['cd', '/home/mailer-domains/'+domain] '&&' ['rndc', 'loadkeys', domain])
                                                                 ^
SyntaxError: invalid syntax


>>> subprocess.call(['cd', '/home/mailer-domains/'+domain], '&&' ['rndc', 'loadkeys', domain])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: string indices must be integers


>>> subprocess.call(['cd', '/home/mailer-domains/'+domain], ['rndc', 'loadkeys', domain])     
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.4/subprocess.py", line 537, in call
    with Popen(*popenargs, **kwargs) as p:
  File "/usr/local/lib/python3.4/subprocess.py", line 767, in __init__
    raise TypeError("bufsize must be an integer")
TypeError: bufsize must be an integer


>>> subprocess.call(['cd', '/home/mailer-domains/'+domain] ['rndc', 'loadkeys', domain])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: list indices must be integers, not tuple


>>> subprocess.call(['cd', '/home/mailer-domains/'+domain] +['rndc', 'loadkeys', domain])
cd: too many arguments
2


>>> ps = subprocess.Popen((['cd', '/home/mailer-domains/'+domain]), stdout = subprocess.PIPE)        
>>> output = subprocess.check_output((['rndc', 'loadkeys', domain]), stdin=ps.stdout)
rndc: 'loadkeys' failed: not found
no matching zone 'lecomm.com' in any view
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.4/subprocess.py", line 620, in check_output
    raise CalledProcessError(retcode, process.args, output=output)
subprocess.CalledProcessError: Command '['rndc', 'loadkeys', 'lecomm.com']' returned non-zero exit status 1


>>> output = subprocess.check_output((['rndc', 'loadkeys', domain]), stdin=ps.stdout, stdout=PIPE)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'PIPE' is not defined

如何通过 Python3 subprocess 正确发送 2 个管道命令？

Answer 1

您根本不需要管道，只需将cwd 传递给子进程：

subprocess.call(['rndc', 'loadkeys', domain],cwd='/home/mailer-domains/'+domain)

如果您确实想要更改的不仅仅是子进程的目录，您应该使用os.chdir。

Answer 2

答案可以在subprocess documentation找到。

subprocess 模块中的函数通常不调用 shell 来解释命令，而是使用给定的参数直接调用它们！可以使用参数shell=True（Python 文档中的示例）覆盖此行为：

output = check_output("dmesg | grep hda", shell=True)

但是，如果命令和参数不固定但取决于用户输入，则不建议这样做。然后，执行此操作的正确方法是使用两个 Popen 调用并手动构建管道（代码示例再次来自 Python 文档）：

p1 = Popen(["dmesg"], stdout=PIPE)
p2 = Popen(["grep", "hda"], stdin=p1.stdout, stdout=PIPE)
p1.stdout.close()  # Allow p1 to receive a SIGPIPE if p2 exits.
output = p2.communicate()[0]