August 2018
Beginner to intermediate
382 pages
7h 14m
Chinese
Content preview from Perl语言入门
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90
第
5
章
输入与输出
先前为了习题的需要，我们已经介绍过输入
/
输出（
input/output , I/O
）的一些用法。
本章将要介绍日常编程中会遇到的大部分
I/O
问题，差不多
80%
左右吧。如果你已经
知道标准输入、标准输出以及标准错误这三个概念，很好，略有超前。如果不熟，请
仔细学习本章。现在，你只要知道“键盘”就是“标准输入”，“屏幕”就是“标准
输出”。
读取标准输入
读取标准输入流相当简单，我们在前面已经用过行输入操作符
<STDIN>
。在标量上下
文中，它会返回标准输入的下一行：
$line = <STDIN>; #
读取下一行
chomp($line); #
截掉最后的换行符
chomp($line = <STDIN>); #
习惯用法，效果同上
我们之所以称
<STDIN>
为行输入操作符，是因为它真的是每次读取一行，用一对尖括
号表示。被它包围的文件句柄（
filehandle
）表示数据来源，本章稍后会讲解文件句柄
的详细概念。
由于行输入操作符在读到文件结尾，没有可读内容的时候会返回
undef
，所以借此可
以跳出循环：
while (defined($line = <STDIN>)) {
print "I saw $line";
}
输入与输出 ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.