在shell有哪些呢＆QUOT; 2 - ;＆放大器1 QUOT;意思？ [英] In the shell, what does " 2>&1 " mean?

问题描述

在Unix外壳，如果我想结合标准错误和标准输出到为进一步操作标准输出流，我可以追加我的命令的末尾以下内容：

In a Unix shell, if I want to combine stderr and stdout into the stdout stream for further manipulation, I can append the following on the end of my command:

2>&1

所以，如果我想使用从克输出头+ +，我可以做这样的事情：

So, if I want to use "head" on the output from g++, I can do something like this:

g++ lots_of_errors 2>&1 | head

所以我只能看到前几个错误。

so I can see only the first few errors.

我总是很难记住这一点，我经常得去看看它，它主要是因为我不完全理解这个特殊的伎俩的语法。有人可以打破这种并通过字符解释字符是什么2>＆安培; 1？指

I always have trouble remembering this, and I constantly have to go look it up, and it is mainly because I don't fully understand the syntax of this particular trick. Can someone break this up and explain character by character what "2>&1" means?

推荐答案

文件描述符1是标准输出（stdout）。结果
文件描述符2是标准错误（错误）。

File descriptor 1 is the standard output (stdout).
File descriptor 2 is the standard error (stderr).

下面是要记住这个结构（尽管它并不完全准确）的一种方法：首先， 2→1 可能看起来像标准错误重定向到标准输出的好办法。但是，它实际上是作为PTED间$ P $标准错误重定向到一个名为 1 文件。 ＆安培; 表示接下来是文件描述符，而不是文件名。因此，结构变为： 2 - ;＆放大器; 1

Here is one way to remember this construct (although it is not entirely accurate): at first, 2>1 may look like a good way to redirect stderr to stdout. However, it will actually be interpreted as "redirect stderr to a file named 1". & indicates that what follows is a file descriptor and not a filename. So the construct becomes: 2>&1.

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