"select((select(s)，$ | = 1)[0]))"是什么意思?在Perl做? [英] What does "select((select(s),$|=1)[0])" do in Perl?

问题描述

我已经看到了用Perl编写的一些可怕的代码，但是我无法做到这一点:

I've seen some horrific code written in Perl, but I can't make head nor tail of this one:

select((select(s),$|=1)[0])

这是我们用来与服务器通信的一些网络代码，我认为这与缓冲有关(因为它设置了$|).

It's in some networking code that we use to communicate with a server and I assume it's something to do with buffering (since it sets $|).

但是我不知道为什么有多个select调用或数组引用.有人可以帮我吗?

But I can't figure out why there's multiple select calls or the array reference. Can anyone help me out?

推荐答案

这是一个讨厌的小习惯，用于在STDOUT以外的文件句柄上设置自动刷新.

It's a nasty little idiom for setting autoflush on a filehandle other than STDOUT.

select()接受提供的文件句柄，并(基本上)用它替换STDOUT，并在完成后返回旧的文件句柄.

select() takes the supplied filehandle and (basically) replaces STDOUT with it, and it returns the old filehandle when it's done.

因此，(select($s),$|=1)重定向文件句柄(记住select返回旧的文件句柄)，并设置自动刷新($| = 1).它在列表((...)[0])中执行此操作，并返回第一个值(这是select调用的结果-原始STDOUT)，然后将 that 传递回另一个select恢复原始的STDOUT文件句柄. ew.

So (select($s),$|=1) redirects the filehandle (remember select returns the old one), and sets autoflush ($| = 1). It does this in a list ((...)[0]) and returns the first value (which is the result of the select call - the original STDOUT), and then passes that back into another select to reinstate the original STDOUT filehandle. Phew.

但是现在您了解了(嗯，也许;))，请改为执行此操作:

But now you understand it (well, maybe ;)), do this instead:

use IO::Handle;
$fh->autoflush;

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