direnv-fetchurl - Man Page
Fetch a URL to disk
Synopsis
direnv fetchurl <url> [<integrity-hash>]
Description
This command downloads the given URL into a fixed disk location, based on the content of the retrieved file.
This has been introduced to avoid a dependency on curl
or wget
, while also promoting a more secure way to fetch data from the Internet. Use this instead of curl <url> | sh
.
This command has two modes of operation:
- Just pass the URL to discover the integrity hash.
- Pass the URL and the integrity hash to get back the on-disk location.
Since the on-disk location is based on the hash, it also acts as a cache. One implication of this design is that URLs must be stable and always return the same content.
Downloaded files are marked as read-only and executable so it can also be used to fetch and execute static binaries.
Options
<url>
A HTTP URL that returns content on HTTP GET requests. 301 and other
redirects are followed.
<integrity-hash>
When passed, the integrity of the retrieved content will be validated
against the given hash. The hash encoding is based on the SRI W3C
specificiation (see ⟨https://www.w3.org/TR/SRI/⟩ ).
Output
direnv fetchurl outputs different content based on the argument.
If the integrity-hash
is being passed, it will output the path to the on-disk location, if the retrieval was successful.
If only the url
is being passed, it will output the hash as well as some human-readable instruction. If stdout is not a tty, only the hash will be displayed.
Example
$ ./direnv fetchurl https://releases.nixos.org/nix/nix-2.3.7/install Found hash: sha256-7Gxl5GzI9juc/U30Igh/pY+p6+gj5Waohfwql3jHIds= Invoke fetchurl again with the hash as an argument to get the disk location: direnv fetchurl "https://releases.nixos.org/nix/nix-2.3.7/install" "sha256-7Gxl5GzI9juc/U30Igh/pY+p6+gj5Waohfwql3jHIds=" #=> /home/zimbatm/.cache/direnv/cas/sha256-7Gxl5GzI9juc_U30Igh_pY+p6+gj5Waohfwql3jHIds=
Environment Variables
XDG_CACHE_HOME
This variable is used to select the on-disk location of the fetched URLs
as $XDG_CACHE_HOME/direnv/cas
. If XDG_CACHE_HOME is unset or empty,
defaults to $HOME/.cache
.
Copyright
MIT licence - Copyright (C) 2019 @zimbatm and contributors