[Nix-dev] nix-prefetch-url and sha256sum differs

[Shea Levy]

nix-prefetch-url prints out the base32 flat hash. There should be some flag to nix-hash to print base32, but it's equivalent to the hex hash.

On Apr 1, 2013, at 4:42, Bjørn Forsman <bjorn.forsman at gmail.com> wrote:

> On 1 April 2013 10:19, Marc Weber <marco-oweber at gmx.de> wrote:
>>> When I run sha256sum on the downloaded file I get the correct result:
>> nix-hash --type sha256 [--flat] file
>> 
>> I don't know why the output differs  from the sha256sum tool.
> 
> $ nix-hash --type sha256
> /nix/store/6alqcyg5qayvwv90vqay1kqxq40mqmm0-lighttpd-1.4.32.tar.gz
> 9095cdc75e33d80f2c3e076b2fce1a2aac5b5b090cacbbe035bce09be80108ee
> 
> $ nix-hash --type sha256 --flat
> /nix/store/6alqcyg5qayvwv90vqay1kqxq40mqmm0-lighttpd-1.4.32.tar.gz
> 0765e07dac432393dea3950639d5ba646ded95a9408ad002e54b3353ab6b9645
> 
> $ sha256sum /nix/store/6alqcyg5qayvwv90vqay1kqxq40mqmm0-lighttpd-1.4.32.tar.gz
> 0765e07dac432393dea3950639d5ba646ded95a9408ad002e54b3353ab6b9645
> /nix/store/6alqcyg5qayvwv90vqay1kqxq40mqmm0-lighttpd-1.4.32.tar.gz
> 
> So the --flat argument must be passed for it to behave like sha256sum.
> 
> [Reading man nix-hash]
> 
> "The hash is computed over a serialisation of each path: a dump of the
> file system tree rooted at the path. This allows directories and
> symlinks to be hashed as well as regular files. The dump is in the NAR
> format produced by nix-store --dump. Thus, nix-hash path yields the
> same cryptographic hash as nix-store --dump path | md5sum."
> 
> So now I'm thinking that nix-prefetch-url does the same, i.e. hashes
> the "serialisation" of the path. But no, it doesn't behave like
> nix-hash, neither with or without --flat:
> 
> $ nix-prefetch-url --type sha256
> http://download.lighttpd.net/lighttpd/releases-1.4.x/lighttpd-1.4.32.tar.gz
> [...]
> path is ‘/nix/store/6alqcyg5qayvwv90vqay1kqxq40mqmm0-lighttpd-1.4.32.tar.gz’
> 0icndfmm6csbwl1d12j0m6aysvb4pbakj1lmlgg968s3miyy0r87
> 
> $ nix-hash --type sha256
> /nix/store/6alqcyg5qayvwv90vqay1kqxq40mqmm0-lighttpd-1.4.32.tar.gz
> 9095cdc75e33d80f2c3e076b2fce1a2aac5b5b090cacbbe035bce09be80108ee
> 
> $ nix-hash --type sha256 --flat
> /nix/store/6alqcyg5qayvwv90vqay1kqxq40mqmm0-lighttpd-1.4.32.tar.gz
> 0765e07dac432393dea3950639d5ba646ded95a9408ad002e54b3353ab6b9645
> 
> Best regards,
> Bjørn Forsman
> _______________________________________________
> nix-dev mailing list
> nix-dev at lists.science.uu.nl
> http://lists.science.uu.nl/mailman/listinfo/nix-dev