plucky (1) nix-prefetch-url.1.gz

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)