August 2018
Beginner to intermediate
382 pages
7h 14m
Chinese
Content preview from Perl语言入门
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目录操作
｜
233
# relative to the current working directory
open my $fh, '<:utf8', 'relative/path.txt'
如果不是在
shell
或命令行终端启动程序，那它的当前工作目录可能会不同。在编辑
器内部调用某个程序，那它的当前工作目录很可能跟保存程序文件的目录不同。而
用
cron
定期启动运行的程序同样也会如此。
当前工作目录并不关心程序保存位置。下面两条命令都是运行当前目录下的
my_
program
程序：
$
./show_my_cwd
$
perl show_my_cwd
但你也可以从其他目录运行这个程序，只要给出程序的完整路径即可：
$
/home/fred/show_my_cwd
$
perl /home/fred/show_my_cwd
如果将程序放在
shell
可以搜索到的目录中，那就可以不加路径，直接启动程序：
$
show_my_cwd
我们可以用标准模块之一的
File::Spec
实现相对路径和绝对路径之间的相互
转换。
修改工作目录
如果你不希望当前工作目录保持在程序文件所在目录，可以用
chdir
操作符修改，它
的用法和
shell
里的
cd
命令一样：
chdir '/etc' or die "cannot chdir to /etc: $!";
由于这是一个对操作系统的调用，所以出错时会设定
$!
的值。如果
chdir
返回假，
则表示修改失败，应该立即检查
$!
中的错误原因。
由
Perl ...
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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.