“使用警告"与“#!/usr/bin/perl -w"有区别吗? [英] 'use warnings' vs. '#!/usr/bin/perl -w' Is there a difference?

问题描述

我读到最好使用警告；而不是在shebang的末尾放置-w.

I read that it is better to use warnings; instead of placing a -w at the end of the shebang.

两者有什么区别?

推荐答案

warnings pragma 是命令行标志 -w 的替代品，但 pragma 仅限于封闭块，而标志是全局的.有关详细信息和内置警告类别列表，请参阅 perllexwarn.

– warnings 文档

use warnings的优点是可以关闭，并且只影响直接作用域.

The advantage of use warnings is that it can be switched off, and only affects the immediate scope.

以使用会发出警告的操作的模块为例:

Consider for example a module that uses operations that would emit warnings:

package Idiotic;
sub stuff {
    1 + undef;
}

然后我们会收到警告

#!perl -w
use Idiotic; # oops, -w is global

Idiotic::stuff();

但不要收到任何警告

#!perl
use warnings;  # pragmas are scoped, yay!
use Idiotic;

Idiotic::stuff();

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