用管道链接几个 Popen 命令

问题描述

我知道如何使用 cmd = subprocess.Popen 然后 subprocess.communicate 来运行命令.大多数时候，我使用一个用 shlex.split 标记的字符串作为 Popen 的 'argv' 参数.以ls -l"为例:

导入子流程进口shlex打印 subprocess.Popen(shlex.split(r'ls -l')，stdin = subprocess.PIPE，stdout = subprocess.PIPE，stderr = subprocess.PIPE).communicate()[0]

但是，管道似乎不起作用...例如，以下示例返回注意:

导入子流程进口shlexprint subprocess.Popen(shlex.split(r'ls -l | sed "s/a/b/g"'), stdin = subprocess.PIPE, stdout = subprocess.PIPE, stderr = subprocess.PIPE).communicate()[0]

你能告诉我我做错了什么吗?

谢谢

解决方案

我想你想在这里实例化两个单独的 Popen 对象，一个用于ls"，另一个用于sed".您需要将第一个 Popen 对象的 stdout 属性作为 stdin 参数传递给第二个 Popen 对象.

例子:

p1 = subprocess.Popen('ls ...', stdout=subprocess.PIPE)p2 = subprocess.Popen('sed ...', stdin=p1.stdout, stdout=subprocess.PIPE)打印 p2.communicate()

如果你有更多命令，你可以继续这样链接:

p3 = subprocess.Popen('prog', stdin=p2.stdout, ...)

有关如何使用子流程的更多信息，请参阅子流程文档.p>

I know how to run a command using cmd = subprocess.Popen and then subprocess.communicate. Most of the time I use a string tokenized with shlex.split as 'argv' argument for Popen. Example with "ls -l":

import subprocess
import shlex
print subprocess.Popen(shlex.split(r'ls -l'), stdin = subprocess.PIPE, stdout = subprocess.PIPE, stderr = subprocess.PIPE).communicate()[0]

However, pipes seem not to work... For instance, the following example returns noting:

import subprocess
import shlex
print subprocess.Popen(shlex.split(r'ls -l | sed "s/a/b/g"'), stdin = subprocess.PIPE, stdout = subprocess.PIPE, stderr = subprocess.PIPE).communicate()[0]

Can you tell me what I am doing wrong please?

Thx

解决方案

I think you want to instantiate two separate Popen objects here, one for 'ls' and the other for 'sed'. You'll want to pass the first Popen object's stdout attribute as the stdin argument to the 2nd Popen object.

Example:

p1 = subprocess.Popen('ls ...', stdout=subprocess.PIPE)
p2 = subprocess.Popen('sed ...', stdin=p1.stdout, stdout=subprocess.PIPE)
print p2.communicate()

You can keep chaining this way if you have more commands:

p3 = subprocess.Popen('prog', stdin=p2.stdout, ...)

See the subprocess documentation for more info on how to work with subprocesses.