NIX-PREFETCH-URL(1) | Command Reference | NIX-PREFETCH-URL(1) |
nix-prefetch-url - copy a file from a URL into the store and print its hash
nix-prefetch-url [--version] [--type hashAlgo] [--print-path] [--unpack] [--name name] url [hash]
The command nix-prefetch-url downloads the file referenced by the URL url, prints its cryptographic hash, and copies it into the Nix store. The file name in the store is hash-baseName, where baseName is everything following the final slash in url.
This command is just a convenience for Nix expression writers. Often a Nix expression fetches some source distribution from the network using the fetchurl expression contained in Nixpkgs. However, fetchurl requires a cryptographic hash. If you don't know the hash, you would have to download the file first, and then fetchurl would download it again when you build your Nix expression. Since fetchurl uses the same name for the downloaded file as nix-prefetch-url, the redundant download can be avoided.
If hash is specified, then a download is not performed if the Nix store already contains a file with the same hash and base name. Otherwise, the file is downloaded, and an error is signaled if the actual hash of the file does not match the specified hash.
This command prints the hash on standard output. Additionally, if the option --print-path is used, the path of the downloaded file in the Nix store is also printed.
--type hashAlgo
--print-path
--unpack
--name name
$ nix-prefetch-url ftp://ftp.gnu.org/pub/gnu/hello/hello-2.10.tar.gz 0ssi1wpaf7plaswqqjwigppsg5fyh99vdlb9kzl7c9lng89ndq1i $ nix-prefetch-url --print-path mirror://gnu/hello/hello-2.10.tar.gz 0ssi1wpaf7plaswqqjwigppsg5fyh99vdlb9kzl7c9lng89ndq1i /nix/store/3x7dwzq014bblazs7kq20p9hyzz0qh8g-hello-2.10.tar.gz $ nix-prefetch-url --unpack --print-path https://github.com/NixOS/patchelf/archive/0.8.tar.gz 079agjlv0hrv7fxnx9ngipx14gyncbkllxrp9cccnh3a50fxcmy7 /nix/store/19zrmhm3m40xxaw81c8cqm6aljgrnwj2-0.8.tar.gz
Eelco Dolstra
Copyright © 2004-2018 Eelco Dolstra
12/12/2020 | Nix 2.3.7 |