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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	every-
       thing 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 re-
       quires 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
	  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
	  result to the	Nix store. The resulting hash can be used  with	 func-
	  tions	such as	Nixpkgss 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.	 Over-
	  riding  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)

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