python 为什么当 args 是序列时 subprocess.Popen 不起作用？
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Why subprocess.Popen doesn't work when args is sequence?
提问by mvladic
I'm having a problem with subprocess.Popen when args parameter is given as sequence.
当 args 参数作为序列给出时，我遇到了 subprocess.Popen 问题。
For example:
例如：
import subprocess
maildir = "/home/support/Maildir"
This works (it prints the correct size of /home/support/Maildir dir):
这有效（它打印 /home/support/Maildir 目录的正确大小）：
size = subprocess.Popen(["du -s -b " + maildir], shell=True,
stdout=subprocess.PIPE).communicate()[0].split()[0]
print size
But, this doesn't work (try it):
但是，这不起作用（尝试一下）：
size = subprocess.Popen(["du", "-s -b", maildir], shell=True,
stdout=subprocess.PIPE).communicate()[0].split()[0]
print size
What's wrong?
怎么了？
回答by
From the documentation
从文档
On Unix, with shell=True: […] If args is a sequence, the first item specifies the command string, and any additional items will be treated as additional arguments to the shell itself. That is to say, Popen does the equivalent of:
Popen(['/bin/sh', '-c', args[0], args[1], ...])
在 Unix 上，使用 shell=True: [...] 如果 args 是一个序列，则第一项指定命令字符串，任何附加项都将被视为 shell 本身的附加参数。也就是说，Popen 的作用相当于：
Popen(['/bin/sh', '-c', args[0], args[1], ...])
Which translates in your case to:
这在你的情况下转化为：
Popen(['/bin/sh', '-c', 'du', '-s', '-b', maildir])
This means that -s, -band maildirare interpreted as options by the shell, not by du(try it on the shell commandline!).
这意味着-s,-b和maildir被shell解释为选项，而不是du（在shell命令行上尝试！）。
Since shell=Trueis not needed in your case anyway, you could just remove it:
由于shell=True无论如何在您的情况下都不需要，您可以将其删除：
size = subprocess.Popen(['du', '-s', '-b', maildir],
stdout=subprocess.PIPE).communicate()[0].split()[0]
Alternatively you could just use your orignal approach, but you don't need a list in that case. You would also have to take care of spaces in the directory name:
或者，您可以只使用您的原始方法，但在这种情况下您不需要列表。您还必须注意目录名称中的空格：
size = subprocess.Popen('du -s -b "%s"' % maildir, shell=True,
stdout=subprocess.PIPE).communicate()[0].split()[0]
回答by YOU
From document,
从文档，
On Unix, with shell=True: If args is a string, it specifies the command string to execute through the shell. If args is a sequence, the first item specifies the command string, and any additional items will be treated as additional shell arguments.
在 Unix 上，shell=True：如果 args 是 string，则它指定要通过 shell 执行的命令字符串。如果 args 是一个序列，则第一项指定命令字符串，任何附加项都将被视为附加的 shell 参数。
So, Try
所以，试试
subprocess.Popen("du -s -b " + maildir, ...
or
或者
subprocess.Popen(["du","-s","-b",maildir], ...
回答by SilentGhost
it should be ["du", "-s", "-b", maildir]
它应该是 ["du", "-s", "-b", maildir]
