How can I get the hash of fetchzip?

1

I know I can just run it with a wrong hash. Is there any way to do that in a script? I thought nix-prefetch-url doesn’t support extraPostFetch.

2

Did you try the --unpack option?

3

Yes, I did. How can I use it with extraPostFetch?

4

Right, nix-prefetch-url --unpack can only work for common fetchzip without extraPostFetch, as there is no way to pass that data to the utility.

Depending on the use case, I usually just change the hash to all zeroes (or an empty string on newer Nix) and Nix will tell me the correct hash. Then I change the hash to the printed one manually.

Other times, especially when updating a package, I use update-source-version from common-updater-scripts, which changes the hash in the Nix expression for me to one corresponding to the given version.

Then there is nix-prefetch from the eponymous package should do what nix-prefetch-url does but takes the data from an attribute so it should support extraPostFetch. I have no experience with that, as I prefer to rely on manual TOFU or update-source-version.

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5

Thanks for your tips!

6

I’d try nix-prefetch-url -A the-attribute.path.that-you-want-to-fetch.

EDIT: oh, the option isn’t documented in man nix-prefetch-url

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