Add automated download script

2020/download.sh

@@ -0,0 +1,26 @@
+#!/bin/bash
+
+if [[ -z $AOC_SESSION ]]; then
+	echo "AOC_SESSION not set"
+	exit 1
+fi
+
+if [[ $# -ge 1 ]]; then
+	# Get rid of leading zeroes
+	(( DAY = $1 * 1 ))
+else
+	DAY=$(date +%-d)
+fi
+
+TARGET_FILE=$(printf "inputs/%02d.txt" "$DAY")
+
+echo "Going to download day $DAY to $TARGET_FILE"
+
+if [[ -s $TARGET_FILE ]]; then
+	echo "Target file exists"
+else
+	curl --output "$TARGET_FILE" \
+		--header "Cookie: session=$AOC_SESSION" \
+		--fail \
+		"https://adventofcode.com/2020/day/$DAY/input"
+fi