jammy (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. 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)