Simplify pull_rib.sh, also works on macOS

Author: viktb

hack/pull_rib.sh

@@ -1,9 +1,6 @@
 #!/usr/bin/env bash
 set -euo pipefail
 
-BASE_URL="http://archive.routeviews.org/bgpdata"
-TIMESTAMP=$((($(date -u +%s)-3600)/7200*7200))
-YEAR=$(date -u -d "@${TIMESTAMP}" +%Y)
-MONTH=$(date -u -d "@${TIMESTAMP}" +%m)
-FILENAME=$(curl -fsSL "${BASE_URL}/${YEAR}.${MONTH}/RIBS/" | grep -oE 'rib\.[0-9]{8}\.[0-9]{4}\.bz2' | tail -n 1)
-wget "${BASE_URL}/${YEAR}.${MONTH}/RIBS/${FILENAME}"
+base_url="http://archive.routeviews.org/bgpdata"
+filename=$(curl -fsSL "${base_url}/$(date +%Y.%m)/RIBS/" | grep -oE 'rib\.[0-9]{8}\.[0-9]{4}\.bz2' | tail -n 1)
+curl -fSLO "${base_url}/$(date +%Y.%m)/RIBS/${filename}"