colloquial language - Is the word 「やんな」positive or negative?

I found that in a website 〜やんな is a colloquial form of 〜やるな　meaning 'Don't do...'

However, I have seen the word in a manga with the following sentence.

A: おい　あかりを消してやんな。新入りさんがまぶしくてねむれんといかん。

B: じゃあ　消すぜ

While B speaking, he also turning off the light.

So, is the word can be both positive and negative?

Answer

The particle な indeed has both meanings: "Don't do ～" and "Do ～". From デジタル大辞泉:

• １ 動詞・動詞型助動詞の終止形、ラ変型活用語の連体形に付く。禁止の意を表す。「油断する―」「まだ帰る―」「かの尼君などの聞かむに、おどろおどろしく言ふ―」〈源・夕顔〉



• ２ 《補助動詞「なさる」の命令形「なさい」の省略形》動詞・動詞型助動詞の連用形に付く。命令の意を表す。「早く行き―」「好きなようにやり―」

To distinguish, な means "don't" when it follows the dictionary-form, and "do" when it follows the masu-stem.

• するな。 = Don't do it.
  しな。 = しなさい。 = Do it.


• 歩くな。 = Don't walk.
  歩きな。 = 歩きなさい。 = Walk.


• 食べるな。 = Don't eat.
  
  食べな。 = 食べなさい。 = Eat.

Using な in positive instead of negative imperative (e.g. 行きな)

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やんな can work as the colloquial form of both やりな and やるな. (やり is the masu-form of やる, which is the subsidiary verb meaning "(do something) for someone" or "Dare do something"). So 消してやんな can both mean "Turn it off (for someone)" and "Don't turn it off".

But these can be distinguished by their accents:

• 消して[やるな]{LHL} ≒ 消して[やんな]{LHL} ≒ Don't turn it off!


• 消して[やりな]{LHH} ≒ 消して[やんな]{LHH} ≒ Turn it off!

Similar examples:

• [かえるな]{HLLL}　≒　[かえんな]{HLLL}　≒ Don't go back/home! (ie, Stay!)


• [かえりな]{LHHH}　≒　[かえんな]{LHHH}　≒ Go back/home!


• [しゃべるな]{LLHLL} ≒ [しゃべんな]{LLHLL} ≒ Shut up!


• [しゃべりな]{LLHHH} ≒ [しゃべんな]{LLHHH} ≒ Say something!

And I think this type of ambiguous colloquial form is found in all ラ行 consonant-stem verbs (走る, 座る, 頑張る, ...).

EDIT: To make sure, 消してやんな in 「あかりを消してやんな。新入りさんがまぶしくてねむれんといかん。」 is 消してやりな. If it were something like 「あかりを消してやんな。新入りさんはまだ勉強がしたいんだ。」 then it would mean 消してやるな. It's purely context-dependent, and I can't tell which is generally more common even after googling 座んな, 走んな, 帰んな, 乗んな, etc.