[英]Why subprocess.Popen doesn't work when args is sequence?
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的问题。
For example: 例如:
import subprocess
maildir = "/home/support/Maildir"
This works (it prints the correct size of /home/support/Maildir dir): 这工作(它打印正确的/ home / support / Maildir目录大小):
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):
size = subprocess.Popen(["du", "-s -b", maildir], shell=True,
stdout=subprocess.PIPE).communicate()[0].split()[0]
print size
What's wrong? 怎么了?
From the documentation 从文档中
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 . 在Unix上,shell = True:[...]如果args是一个序列,第一个项指定命令字符串,任何其他项将被视为shell本身的附加参数 。 That is to say, Popen does the equivalent of: 也就是说,Popen相当于:
Popen(['/bin/sh', '-c', args[0], args[1], ...])
Which translates in your case to: 在您的情况下翻译为:
Popen(['/bin/sh', '-c', 'du', '-s', '-b', maildir])
This means that -s
, -b
and maildir
are 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命令行上尝试它!)。
Since shell=True
is not needed in your case anyway, you could just remove it: 因为在你的情况下不需要shell=True
,你可以删除它:
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. 或者,您可以使用您的原始方法,但在这种情况下您不需要列表。 You would also have to take care of spaces in the directory name: 您还需要处理目录名称中的空格:
size = subprocess.Popen('du -s -b "%s"' % maildir, shell=True,
stdout=subprocess.PIPE).communicate()[0].split()[0]
On Unix, with shell=True : If args is a string , it specifies the command string to execute through the shell. 在Unix上, shell = True :如果args是一个字符串 ,它指定要通过shell执行的命令字符串。 If args is a sequence , the first item specifies the command string, and any additional items will be treated as additional shell arguments. 如果args是一个序列 ,则第一个项指定命令字符串,任何其他项将被视为附加的shell参数。
So, Try 所以,试试吧
subprocess.Popen("du -s -b " + maildir, ...
or 要么
subprocess.Popen(["du","-s","-b",maildir], ...
它应该是["du", "-s", "-b", maildir]
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