Name

       nix-prefetch-url - copy a file from a URL into the store and print its hash

Synopsis

       nix-prefetch-url url [hash] [--type hashAlgo] [--print-path] [--unpack] [--name name]

Description

       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.

Options

       • --type hashAlgo
         Use  the  specified cryptographic hash algorithm, which can be one of md5, sha1, sha256,
         and sha512.

       • --print-path
         Print the store path of the downloaded file on standard output.

       • --unpack
         Unpack the archive (which must be a tarball or zip file) and add the result to  the  Nix
         store.  The  resulting  hash  can  be  used with functions such as Nixpkgs’s fetchzip or
         fetchFromGitHub.

       • --executable
         Set the executable bit on the downloaded file.

       • --name name
         Override the name of the file in the Nix store. By default, this is hash-basename, where
         basename  is  the last component of url.  Overriding the name is necessary when basename
         contains characters that are not allowed in Nix store paths.

Examples

       $ 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

                                                                              nix-prefetch-url(1)