October 2022
Beginner to intermediate
390 pages
7h 5m
Chinese
Content preview from Perl语言入门（第8版）
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目录操作
｜
251
要取得符号链接指向的位置，请使用
readlink
函数。它会返回符号链接指向的路
径，如果给出的文件名不是符号链接，则返回
undef
：
my $where = readlink 'carroll'; #
得到
"dodgson"
my $perl = readlink '/usr/local/bin/perl'; #
告诉你实际的
perl
程序究竟躲在何处
这两种链接都可以用
unlink
移除，你现在该了解这个名字的含义了吧。
unlink
只是
从目录里移除该文件名的链接条目，并将它的链接计数递减，必要时再释放
inode
。
创建和删除目录
要在现有目录下创建新目录是件很容易的事，只需调用
mkdir
函数即可：
mkdir 'fred', 0755 or warn "Cannot make fred directory: $!";
没错，返回值为真表示成功，失败时则会设定
$!
的值。
可第二个参数
0755
是什么意思呢？它代表目录的初始权限（将来随时可再更改）。
写成八进制数值，是因为它会被解释成三位一组的
Unix
权限值，适合用八进制来表
达。没错，就算在
Windows
或
MacPerl
上，你也需要略懂
Unix
的权限值，才有办法
使用
mkdir
函数。
0755
是个不错的设定，因为它赋予你所有常用权限，而其他人只能
读取却不能更改任何内容。
注意
mkdir
函数并不要求你用八进制写这个值，它只是需要某个数字（直接量或运算
结果都行）。但除非你能快速心算出八进制的 ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
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.