在 Perl 中，.pm(Perl 模块)和 .pl(Perl 脚本)文件有什么区别? [英] In Perl, what is the difference between a .pm (Perl module) and .pl (Perl script) file?

问题描述

.pm(Perl 模块)和 .pl(Perl 脚本)文件有什么区别?

What is the Difference between .pm (Perl module) and .pl (Perl script) file?

还请告诉我为什么我们从文件中返回 1.如果返回 2 或其他任何东西，它不会产生任何错误，那么为什么我们从 Perl 模块返回 1 ?

Please also tell me why we return 1 from file. If return 2 or anything else, it's not generating any error, so why do we return 1 from Perl module?

推荐答案

在本质上，您使用的文件扩展名对 perl 如何解释这些文件没有影响.

At the very core, the file extension you use makes no difference as to how perl interprets those files.

然而，将模块放在 .pm 文件中遵循特定的目录结构，遵循包名提供了方便.所以，如果你有一个模块 Example::Plot::FourD 并且你把它放在 Example/Plot/FourD.pm 目录下你的 @INC，然后是 use 和 require 在给定包名时会做正确的事情，如use Example::Plot::FourD.

However, putting modules in .pm files following a certain directory structure that follows the package name provides a convenience. So, if you have a module Example::Plot::FourD and you put it in a directory Example/Plot/FourD.pm in a path in your @INC, then use and require will do the right thing when given the package name as in use Example::Plot::FourD.

该文件必须返回 true 作为最后一条语句以指示任何初始化代码的成功执行，因此习惯上以 1; 结束此类文件，除非您确定否则它会返回 true.但是最好只放1;，以防您添加更多语句.

The file must return true as the last statement to indicate successful execution of any initialization code, so it's customary to end such a file with 1; unless you're sure it'll return true otherwise. But it's better just to put the 1;, in case you add more statements.

如果 EXPR 是一个裸字，require 假定一个.pm"；扩展并替换::"用/"；在您的文件名中，以便于加载标准模块.这种加载模块的形式不会改变您的命名空间.

If EXPR is a bareword, the require assumes a ".pm" extension and replaces "::" with "/" in the filename for you, to make it easy to load standard modules. This form of loading of modules does not risk altering your namespace.

use 所做的就是从提供的包名中找出文件名，require 在 BEGIN 块中并调用 在包上导入.没有什么可以阻止您不使用 use 而是手动执行这些步骤.

All use does is to figure out the filename from the package name provided, require it in a BEGIN block and invoke import on the package. There is nothing preventing you from not using use but taking those steps manually.

例如，下面我将 Example::Plot::FourD 包放在一个名为 t.pl 的文件中，将它加载到文件 中的脚本中s.pl.

For example, below I put the Example::Plot::FourD package in a file called t.pl, loaded it in a script in file s.pl.

C:Temp> cat t.pl
package Example::Plot::FourD;

use strict; use warnings;

sub new { bless {} => shift }

sub something { print "something
" }

"Example::Plot::FourD"

C:Temp> cat s.pl
#!/usr/bin/perl
use strict; use warnings;

BEGIN {
    require 't.pl';
}

my $p = Example::Plot::FourD->new;
$p->something;


C:Temp> s
something

这个例子表明模块文件不必以1结尾，任何真值都可以.

This example shows that module files do not have to end in 1, any true value will do.

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