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.  The hash is printed using base-32 unless --type md5  is
       specified,  in  which case it’s printed using base-16.  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.
          The default is sha256.

       •  --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)