lix/scripts/nix-prefetch-url.in
Eelco Dolstra 21655a70f5 * Channels. These allow you to stay current with an evolving set of
Nix expressions.

  To subscribe to a channel (needs to be done only once):

    nix-channel --add \
      http://catamaran.labs.cs.uu.nl/dist/nix/channels/nixpkgs-unstable

  This just adds the given URL to ~/.nix-channels (which can also be
  edited manually).

  To update from all channels:

    nix-channel --update

  This fetches the latest expressions and pulls cache manifests.  The
  default Nix expression (~/.nix-defexpr) is made to point to the
  conjunction of the expressions downloaded from all channels.

  So to update all installed derivations in the current user
  environment:

    nix-channel --update
    nix-env --upgrade '*'

  If you are really courageous, you can put this in a cronjob or
  something.

  You can subscribe to multiple channels.  It is not entirely clear
  what happens when there are name clashes between derivations from
  different channels.  From nix-env/main.cc it appears that the one
  with the lowest (highest?) hash will be used, which is pretty
  meaningless.
2004-04-21 14:54:05 +00:00

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#! @shell@ -e
url=$1
if test -z "$url"; then
echo "syntax: nix-prefetch-url URL" >&2
exit 1
fi
# !!! race? should be relatively safe, `svn export' barfs if $tmpPath exists.
tmpPath1=@storedir@/nix-prefetch-url-$$
# Perform the checkout.
@curl@ --fail --location --max-redirs 20 "$url" > $tmpPath1
# Compute the hash.
hash=$(@bindir@/nix-hash --flat $tmpPath1)
echo "hash is $hash" >&2
# Rename it so that the fetchsvn builder can find it.
tmpPath2=@storedir@/nix-prefetch-url-$hash
test -e $tmpPath2 || mv $tmpPath1 $tmpPath2 # !!! race
# Create a Nix expression that does a fetchsvn.
storeExpr=$( \
echo "(import @datadir@/nix/corepkgs/fetchurl) \
{url = $url; md5 = \"$hash\"; system = \"@system@\";}" \
| nix-instantiate -)
# Realise it.
finalPath=$(nix-store -qnB --force-realise $storeExpr)
echo "path is $finalPath" >&2
rm -rf $tmpPath2 || true
echo $hash