f3s/shelly: rack-fan boot-time auto-on rc.d service + plug control script

Add shellyfans rc.d service (boot-time auto-on for the rack fans on the
Shelly Plug M Gen 3 at 192.168.1.28) and a standalone shelly-plug.sh
helper to query/control the plug over its HTTP RPC API.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

1 files changed, 87 insertions, 0 deletions

diff --git a/playground/shelly-plug.sh b/playground/shelly-plug.sh
new file mode 100755
index 0000000..5619f93
--- /dev/null
+++ b/playground/shelly-plug.sh
@@ -0,0 +1,87 @@
+#!/bin/sh
+# Control and query a Shelly Plug M Gen 3 via its HTTP RPC API.
+#
+# Usage:
+#   shelly-plug.sh [host] <command>
+#
+# Commands:
+#   status   Show power, voltage, current, energy and temperature
+#   on       Turn the plug on
+#   off      Turn the plug off
+#   toggle   Toggle the plug
+#   info     Show device info (model, firmware, mac)
+#
+# The host defaults to 192.168.1.28 and can be overridden by the first
+# argument or the SHELLY_HOST environment variable.
+#
+# If the device has authentication enabled, the password is read from the
+# SHELLY_PASS environment variable, or from ~/.shelly_plug if that is unset
+# (the username is always "admin" on Shelly Gen3). Digest auth is used
+# automatically when a password is available.
+
+set -eu
+
+DEFAULT_HOST="192.168.1.28"
+PASS_FILE="${HOME}/.shelly_plug"
+
+# Argument forms:
+#   (none)            -> host=default, command=status
+#   <command>         -> host=default, command=<command>
+#   <host> <command>  -> explicit host and command
+if [ "$#" -ge 2 ]; then
+	HOST="$1"
+	CMD="$2"
+elif [ "$#" -eq 1 ]; then
+	HOST="${SHELLY_HOST:-$DEFAULT_HOST}"
+	CMD="$1"
+else
+	HOST="${SHELLY_HOST:-$DEFAULT_HOST}"
+	CMD="status"
+fi
+
+BASE="http://${HOST}"
+
+# Resolve the password: SHELLY_PASS wins, otherwise read it from PASS_FILE.
+PASS="${SHELLY_PASS:-}"
+if [ -z "$PASS" ] && [ -r "$PASS_FILE" ]; then
+	PASS="$(head -n 1 "$PASS_FILE" | tr -d '\r\n')"
+fi
+
+# Build optional digest-auth args when a password is available.
+AUTH=""
+if [ -n "$PASS" ]; then
+	AUTH="--digest -u admin:${PASS}"
+fi
+
+rpc() {
+	# shellcheck disable=SC2086
+	curl -s --max-time 5 $AUTH "${BASE}/rpc/$1"
+}
+
+case "$CMD" in
+	status)
+		rpc "Switch.GetStatus?id=0"
+		echo
+		;;
+	on)
+		rpc "Switch.Set?id=0&on=true"
+		echo
+		;;
+	off)
+		rpc "Switch.Set?id=0&on=false"
+		echo
+		;;
+	toggle)
+		rpc "Switch.Toggle?id=0"
+		echo
+		;;
+	info)
+		curl -s --max-time 5 "${BASE}/shelly"
+		echo
+		;;
+	*)
+		echo "Unknown command: $CMD" >&2
+		echo "Use one of: status, on, off, toggle, info" >&2
+		exit 1
+		;;
+esac