August 2018
Beginner to intermediate
382 pages
7h 14m
Chinese
Content preview from Perl语言入门
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106
｜
第
5
章
所以从
Perl 5.6
开始，你可以在
binmode
的第二个参数位置上指定过滤层。比如希望
向
STDOUT
输出
Unicode
编码的字符，就必须提前告之，以便
STDOUT
能够正确处理和
显示：
binmode STDOUT, ':encoding(UTF-8)';
若是不指明，
STDOUT
无法理解拿到的是什么，除非关闭警告功能，否则会提示以下信
息：
Wide character in print at test line 1.
binmode
同样可用于标准输入和标准输出。如果希望标准输入的数据按
UTF-8
编码方
式读取，以下面方式指明：
binmode STDIN, ':encoding(UTF-8)';
异常文件句柄的处理
和其他程序语言一样，
Perl
是无法自己说了算地直接打开操作系统中的文件的，只能
请求操作系统代为处理。如果没有权限读写或者提供的文件名错误，操作系统会拒绝
打开。
如果试着从没有正确打开的文件句柄（或已关闭连接的网络）读取数据，会立即读
到文件结尾（对于你将会在本章看到的各种
I/O
方法而言，这个文件结尾在标量上下
文中就是
undef
，在列表上下文中就是空列表）。如果试图将数据写入这样的文件句
柄，这些数据将被无声抛丢弃。
当然，我们可以避免这种情况。一种办法是用
-w
选项启动程序或者用
warnings
编译
指令，那么在读写异常文件句柄时，
Perl
会发出警告。另一种办法是检查
open
的返
回值，如果打开文件句柄失败会返回假，如果成功则返回真。所以，程序可以写成这 ...
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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.