I read the following inspiration sentance in internet:

"If a writer has a masterpiece within,he had better save it on paper.
Otherwie none of us will ever miss it."
--Steve Martin.

I think the word "all" should be used inplace of "none".

Correct me if am wrong.
No, it's a joke. Steve Martin is a comedian.

Don't expect his sentences to be sensible.
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On the contrary, comedy brings out the wittiest of wordplays!

Anyway, the sentence is correct; if you want to substitute 'none' for 'all', you will also have to change 'ever' with 'never', so as to keep the meaning the same (keep one negation in the sentence instead of introducing an additional one)- however, 'all of us will never miss it' sounds quite a bit awkward, compared to 'none of us will ever miss it' (an alternative might be 'we will never miss it').
Thank you sir,for clarifying my doubt.

My anothe doubt is there should n't be "otherwise" in the sentance(Otherwise, none of us will ever miss it).