带有 heredocs 的 Python 子进程 [英] Python subprocess with heredocs

问题描述

我在玩 Python 的 subprocess 模块，尝试了几个例子，但我似乎无法让 heredoc 语句起作用.

I was playing around with Python's subprocess module, trying a few examples but I can't seem to get heredoc statements to work.

这是我玩的一个简单的例子:

Here is the trivial example I was playing with:

import subprocess
a = "A String of Text"
p = subprocess.Popen(["cat", "<<DATA\n" + a + "\nDATA"])

当我运行上面的代码时出现以下错误:

I get the following error when I run the code above:

cat: <<DATA\nA String of Text\nDATA: No such file or directory

我做错了吗?这甚至可能吗?如果是这样，我将如何去做?

Am I doing it wrong? Is this even possible? If so how would I go about doing it?

更新

只是想说这不应该在真正的 Python 程序中执行，因为有更好的方法可以做到这一点.

Just wanted to say that this should never be performed in a real python program because there are better ways of doing this.

推荐答案

外壳heredoc"支持是外壳功能.subprocess.Popen 默认情况下不会通过 shell 运行您的命令，因此此语法肯定不起作用.

The shell "heredoc" support is a shell feature. subprocess.Popen does not run your command through the shell by default, so this syntax certainly won't work.

然而，因为无论如何你都在使用管道，所以没有必要使用 shell 的 heredoc 支持.只需将您的字符串 a 写入您刚刚启动的进程的标准输入管道.无论如何，这正是 shell 对 heredoc 所做的.

However, since you're using pipes anyway, there isn't any need to use the heredoc support of the shell. Just write your string a to the stdin pipe of the process you just started. This is exactly what the shell would do with the heredoc anyway.

您可以使用 Popen.communicate():

You can do this with Popen.communicate():

p.communicate(a)

communicate() 函数的返回值包含进程的输出(在两个流中，请参阅文档).

The return value of the communicate() function contains the output of the process (in two streams, see the docs).

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