path: root/scripts/nix-prefetch-url.in

#! @shell@ -e

url=$1

if test -z "$url"; then
    echo "syntax: nix-prefetch-url URL" >&2
    exit 1
fi

# !!! race
tmpPath1=@storedir@/nix-prefetch-url-$$

# Test whether we have write permission in the store.  If not, fetch
# to /tmp and don't copy to the store.  This is a hack to make this
# script at least work somewhat in setuid installations.
if ! touch $tmpPath1 2> /dev/null; then
    echo "(cannot write to the store, result won't be cached)" >&2
    dummyMode=1
    tmpPath1=/tmp/nix-prefetch-url-$$ # !!! security?
fi

# 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 fetchurl builder can find it.
if test "$dummyMode" != 1; then
    tmpPath2=@storedir@/nix-prefetch-url-$hash
    test -e $tmpPath2 || mv $tmpPath1 $tmpPath2 # !!! race
fi

# Create a Nix expression that does a fetchurl.
storeExpr=$( \
    echo "(import @datadir@/nix/corepkgs/fetchurl) \
        {url = $url; md5 = \"$hash\"; system = \"@system@\";}" \
    | @bindir@/nix-instantiate -)

# Realise it.
finalPath=$(@bindir@/nix-store -qnB --force-realise $storeExpr)
    
echo "path is $finalPath" >&2

rm -rf $tmpPath1 $tmpPath2 || true

echo $hash

if test -n "$PRINT_PATH"; then
    echo $finalPath
fi