为什么subprocess.check_调用命令总是返回0？

Question

我想从另一个.py文件获取路径名。在

我把那个.py文件叫做

xy=subprocess.check_call(["python","/home/emeks/workspace/ex/ex.py"])

print xy

但是print命令总是打印零（0），但是我想得到路径名。在

我该怎么办

Answer 1

subprocess.check_call()的目的是返回0，或者在被调用进程的退出状态不是0时引发异常：

Run command with arguments. Wait for command to complete. If the return code was zero then return, otherwise raise CalledProcessError.

如果需要读取另一个命令的输出，请改用^{}：

Run command with arguments and return its output as a byte string.

该函数是在Python 2.7中添加的；如果您使用的是早期版本的Python，下面是一个backport：

from subprocess import Popen, PIPE
from subprocess import CalledProcessError as BaseCalledProcessError

class CalledProcessError(BaseCalledProcessError):
    def __init__(self, returncode, cmd, output=None):
        super(CalledProcessError, self).__init__(returncode, cmd)
        self.output = output

def check_output(*popenargs, **kwargs):
    r"""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.

    The arguments are the same as for the Popen constructor.  Example:

    >>> check_output(["ls", "-l", "/dev/null"])
    'crw-rw-rw- 1 root root 1, 3 Oct 18  2007 /dev/null\n'

    The stdout argument is not allowed as it is used internally.
    To capture standard error in the result, use stderr=STDOUT.

    >>> check_output(["/bin/sh", "-c",
    ...               "ls -l non_existent_file ; exit 0"],
    ...              stderr=STDOUT)
    'ls: non_existent_file: No such file or directory\n'
    """
    if 'stdout' in kwargs:
        raise ValueError('stdout argument not allowed, it will be overridden.')
    process = Popen(stdout=PIPE, *popenargs, **kwargs)
    output, unused_err = process.communicate()
    retcode = process.poll()
    if retcode:
        cmd = kwargs.get("args")
        if cmd is None:
            cmd = popenargs[0]
        raise CalledProcessError(retcode, cmd, output=output)
    return output