在Python中使用'dpkg'会导致OSError：[Errno 9]错误的文件描述符

Question

我构建了一个脚本来查找最新版本的Visual Studio Code，下载它并将其安装在带有dpkg的Ubuntu机器上。我没有找到一个像样的Python库，并使用subprocess.call（）来调用Shell命令。这当然可能不是最好的方法，但这也是一个学习项目。

它成功下载文件并将其放在我的〜/ Downloads目录中。当我尝试调用subprocess.call（）时，它会回吐'OSError：[Errno 9] Bad file descriptor'

我知道我的命令字符串是正确的。我可以从CLI调用它。但是当通过子进程调用时它不起作用。

欢迎任何有关这样做的建议。

"""
Python 3 script
Downloads the latest .deb package for installing VSCode, and installs it 
"""
import os               # used to direct where to save downloaded file
import subprocess       # used to derive filepath of CLI arg
import requests         # py3 only
import platform         # used to detect the OS
from urllib.request import urlopen, ContentTooShortError, urlretrieve # py3 version of 'import urllib2'

HOME = os.path.expanduser('~')
filePath = HOME + "/Downloads"
fileName = 'vs_code_most_recent_amd64.deb'
outputName = os.path.join(filePath, fileName)
alreadyDownloaded = False

# used in subprocess calls to suppress stdout or stderr
pipeToDevNull = open(os.devnull, 'w')

def IsDownloadable(url):
    """
    Check of the link passed in is a downloadable file. Used to shortcut the 
    processing so that it doesn't attempt to download a URL that isn't 
    downloadable.  Returns True or False.
    """
    h = requests.head(url, allow_redirects=True)
    header = h.headers
    contentType = header.get('content-type')
    if 'text' in contentType.lower():
        return False
    if 'html' in contentType.lower():
        return False
    return True

def DownloadVSCodePkg(url):
    """
    Downloads the file at the specified URL, save it as the above-defined filename
    """
    u = urlopen(url)

    f = open(outputName, 'wb')
    meta = u.info()

    fileSize = int(meta.get_all("Content-Length")[0])    

    fileSizeDL = 0
    #blockSize = 8192
    blockSize = 16384

    while True:
        buffer = u.read(blockSize)
        if not buffer:
            break
        fileSizeDL += len(buffer)
        f.write(buffer)
        status = r"%10d Bytes [%3.2f%%]" % (fileSizeDL, fileSizeDL * 100. / fileSize)
        status = status + chr(8)*(len(status)+1)
        print("Downloading: {0}".format(status), end="\r", flush=True)
    print("Downloading: {0}".format(status))
    print("Downloaded: {0}".format(fileName))
    f.close()
    del f


def CheckDownloadSuccess():
    """
    returns bool value if the file we want is in the dir specified
    """
    try:
        subprocess.check_call("ls " + outputName, stdout=pipeToDevNull, stderr=pipeToDevNull, shell=True)
        return True
    except subprocess.CalledProcessError:
        return False

def UnpackAndInstall():
    """
    Invokes dpkg from the linux shell and installs VSCode.
    """
    #Detect OS
    linuxDistro = platform.linux_distribution()
    OSType = linuxDistro[0]

    if OSType == 'Ubuntu':
        from apt.debfile import DebPackage
        pkg = DebPackage(outputName)
        command = 'sudo dpkg -i ' + outputName

        #The thing that attempts to unpack:
        try:
            subprocess.check_call(command, stdout=subprocess.STDOUT, stderr=subprocess.STDOUT, shell=True)
        except subprocess.CalledProcessError:
            print("Install Failed.")

def main():
    url = 'https://go.microsoft.com/fwlink/?LinkID=760868'

    alreadyDownloaded = CheckDownloadSuccess()

    if alreadyDownloaded is False:
        if IsDownloadable(url):
            DownloadVSCodePkg(url)            
            # check if the download succeeded, if file doesn't already exist.
            if CheckDownloadSuccess():
                print("Download Successful!\nFile location => " + outputName)
            else:
                print("Download Failed...")

        else:
            print('Link broken: need to update the package resource link.')
    else:
        print("File already exists.")

    UnpackAndInstall()

if __name__ == "__main__":
    main()

这是来自CLI的回溯和错误：

$ python3 setupVSCode.py 

Traceback (most recent call last):
  File "setupVSCode.py", line 192, in <module>
    main()
  File "setupVSCode.py", line 189, in main
    UnpackAndInstall()
  File "setupVSCode.py", line 95, in UnpackAndInstall
    subprocess.call(command, stdout=subprocess.STDOUT, stderr=subprocess.STDOUT, shell=True)
  File "/usr/lib/python3.6/subprocess.py", line 267, in call
    with Popen(*popenargs, **kwargs) as p:
  File "/usr/lib/python3.6/subprocess.py", line 709, in __init__
    restore_signals, start_new_session)
  File "/usr/lib/python3.6/subprocess.py", line 1344, in _execute_child
    raise child_exception_type(errno_num, err_msg, err_filename)
OSError: [Errno 9] Bad file descriptor

Answer 1

qazxsw poi将返回类似：qazxsw poi，你附加os.path.expanduser('~')，导致一条糟糕的道路，如：'C:\\Users\\user.name'

代替：

'/Downloads'

做：

'C:\\Users\\user.name/Downloads\\'

或者最好：

filePath = HOME + "/Downloads"

Answer 2

在与@Steve交谈后，我尝试删除subprocess.call（）上的输出重定向器。

关于删除路径构造中的所有斜杠而不是使用“os.path.join（）”的建议已经实现，并将从此处作为最佳实践。

由于构造的命令在CLI中工作正常，因此需要考虑subprocess.call（）所执行的操作是不同的。它重定向输出。删除后，事情就好了

它现在看起来像这样：

filePath = HOME + "\Downloads"