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)文件之间有什么区别?

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

也请告诉我为什么我们从文件中返回1.如果返回2或其他任何内容，它不会产生任何错误，那么为什么我们要从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

从根本上说，您使用的文件扩展名对于perl解释这些文件的方式没有影响.

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

但是，将模块放在遵循包名称的某个目录结构的.pm文件中会带来方便.因此，如果您有模块Example::Plot::FourD，并将其放在 use 和use Example::Plot::FourD中那样给定包名称时，="http://perldoc.perl.org/functions/require.html" rel ="noreferrer"> require 会做正确的事情.

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.

文件必须作为最后一条语句返回true，以指示任何初始化代码的成功执行，因此习惯上以1;结尾此类文件，除非您确定否则将返回true.但是最好放1;，以防您添加更多的语句.

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是空词，则require假定扩展名为".pm"，并用文件名中的"/"替换"::"，以便于加载标准模块.这种加载模块的形式不会冒更改您的命名空间的风险.

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的全部作用是从提供的程序包名称中找出文件名，在BEGIN块中require将其命名，然后在程序包上调用import.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软件包放在名为t.pl的文件中，并将其加载到文件s.pl中的脚本中.

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\n" }

"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

此示例显示模块文件不必以1结尾，任何真实值都可以.

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

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