什么是/dev/null 2& 1? [英] What is /dev/null 2>&1?

问题描述

我在/etc/cron.daily/apf中找到了这段代码

I found this piece of code in /etc/cron.daily/apf

#!/bin/bash  
/etc/apf/apf -f >> /dev/null 2>&1  
/etc/apf/apf -s >> /dev/null 2>&1  

正在刷新并重新加载防火墙.
我不理解>> /dev/null 2>&1部分.

It's flushing and reloading the firewall.
I don't understand the >> /dev/null 2>&1 part.

将其放在cron中的目的是什么?它覆盖了我的防火墙规则. 我可以安全地删除此Cron作业吗?

What is the purpose of having this in the cron? It's overriding my firewall rules. Can I safely remove this cron job?

推荐答案

>> /dev/null将标准输出(stdout)重定向到/dev/null，并丢弃它.

>> /dev/null redirects standard output (stdout) to /dev/null, which discards it.

(>>似乎是多余的，因为>>表示追加，而>表示截断和写入，并且追加或写入/dev/null具有相同的净效果.我通常只使用出于这个原因.)

(The >> seems sort of superfluous, since >> means append while > means truncate and write, and either appending to or writing to /dev/null has the same net effect. I usually just use > for that reason.)

2>&1将标准错误(2)重定向到标准输出(1)，由于标准输出已被重定向，该错误也会被丢弃.

2>&1 redirects standard error (2) to standard output (1), which then discards it as well since standard output has already been redirected.

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