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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236
｜
第
12
章
习题
以下习题答案参见第
326
页上的“第
12
章习题解答”一节：
1. [15]
编写程序，从命令行取得一串文件名，并汇报这些文件是否可读、可写、可
执行以及是否确实存在。（提示：如果你可以写一个函数，一次做完这些测试会
很方便。）如果文件先被
chmod
为
0
，你的程序会汇报什么？（也就是说，如果
你使用
Unix
系统，
chmod 0 some_file
这样的命令就会把文件标示成不可读、不
可写也不可执行。）在大部分
shell
下，用星号作为参数，代表当前目录下的所
有文件。也就是说，你可以用
./ex12-2 *
这样的命令来向程序一次询问多个要
测试文件的属性。
2. [10]
编写程序，从命令行参数指定的文件中找出最旧的文件并且以天数汇报它已
存在了多久。若列表是空的（也就是命令行中没有提及任何文件），那么它该做
什么？
3. [10]
编写程序，用栈式文件测试操作符列出命令行参数指定的所有文件，看看拥
有者是否是你自己，以及它们是否可读、可写。
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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.