start image and browser on random port

launch.sh

#!/bin/bash

IMAGE="nginx:latest"
CONTAINER_PORT=80
CONTAINER_NAME="my-web-app"

docker rm -f "$CONTAINER_NAME" 2>/dev/null

# -p with only container port = Docker picks a random free host port
docker run -d --name "$CONTAINER_NAME" -p ${CONTAINER_PORT} "$IMAGE"

# Ask Docker which port it assigned
HOST_PORT=$(docker port "$CONTAINER_NAME" ${CONTAINER_PORT}/tcp | head -n1 | cut -d: -f2)
URL="http://localhost:${HOST_PORT}/index.html"

echo "Server running on port $HOST_PORT"

# Wait until reachable
for i in {1..30}; do
    if curl -s -o /dev/null -w "%{http_code}" "$URL" | grep -q "200"; then
        break
    fi
    sleep 0.5
done

case "$(uname -s)" in
    Darwin)  open -a "Google Chrome" "$URL" ;;
    Linux)   google-chrome "$URL" 2>/dev/null || xdg-open "$URL" ;;
esac