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nix-prefetch-url(1)	     General Commands Manual	     nix-prefetch-url(1)

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 al-
     ready  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
	blake3, 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 re-
	sult to the Nix store. The resulting hash can  be  used  with  functions
	such as Nixpkgsas 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 al-
	lowed 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)

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