add script to run command and temp open a port

scripts/openport

@@ -0,0 +1,35 @@
+#!/usr/bin/env bash
+# Credit: u/boxofrox https://discourse.nixos.org/u/boxofrox
+# Ref: https://discourse.nixos.org/t/how-to-temporarily-open-a-tcp-port-in-nixos/12306/3
+USAGE="[Usage] sudo withport <port> <cmd> <args...>"
+
+set -ueo pipefail
+
+open-port() {
+  local port=$1
+  iptables -A INPUT -p tcp --dport $port -j ACCEPT
+}
+
+close-port() {
+  local port=${1:-0}
+  iptables -D INPUT -p tcp --dport $port -j ACCEPT
+}
+
+PORT=$1
+if [[ -z "$PORT" ]]; then
+  echo -e "[!] Port not given\n$USAGE" >&2
+  exit 1
+fi
+shift;  # Drop port argument
+
+if [[ 0 -eq $# ]]; then
+  echo -e "[!] Command not given\n$USAGE" >&2
+  exit 1
+fi
+
+open-port $PORT
+# Ensure port closes if error occurs.
+trap "close-port $PORT" EXIT
+# Run the command as user, not root.
+runuser -u $SUDO_USER -- "$@"
+# Trap will close port.