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)