Add tool to parse prefixes from geolocation feeds

rir-geofeed2prefix

@@ -0,0 +1,42 @@
+#!/bin/bash
+#
+# Copyright (c) 2024 Nagrind </~https://github.com/nagrind>
+#
+# Permission to use, copy, modify, and distribute this software for any
+# purpose with or without fee is hereby granted, provided that the above
+# copyright notice and this permission notice appear in all copies.
+#
+# THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+# OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+#
+
+set -euo pipefail
+
+err() { echo "${@}" 1>&2; exit 1; }
+usage() { err "Usage: $(basename "${0}") [-4|-6] <geofeed>"; }
+
+declare mode=""
+while getopts ":46" opts; do
+  case "${opts}" in
+    4) mode+="\." ;;
+    6) mode+=":" ;;
+    *) usage ;;
+  esac
+done
+shift $((OPTIND-1))
+
+[[ ${#} != 1 ]] && usage
+
+result="$(curl --silent --user-agent "rir-geofeed2prefix/0.0.1" -- "${1}" | \
+  gawk -F ',' '{ if (!/^#/ && tolower($1) ~ /^[0-9a-f].*['"${mode:-\.:}"']/) \
+    print $1 }')"
+
+readarray -t lines <<< "${result}"
+# shellcheck disable=SC2015
+[[ ${#lines[@]} != 0 && -n "${lines[0]}" ]] && echo "${result}" || \
+  err "No entries found"