The cool thing about the Yún is that it comes with a built in web server.

NOTE: At this point, you should know how to connect to your Yún using WiFi and through your server. Also, you should have expanded its memory. [LINK TO PREVIOUS POSTS]

An Arduino sketch consists on a folder with the sketch's name and a file with an ino extension.

When you make a sketch with the Arduino Yún, if you create a www folder inside your sketch folder- next to the ino file- any additional content inside will be copied on the Linino side in the /sd/arduino/www/<sketch_name>. As long as you are connected to the Arduino over the network port, the IDE will do this for you.

Then, the contents are accessible via browser in the url:

http://<board_name>.local/sd/<sketch_name>

So, I named one of my Yún goluino. And I created a sketch with the name yun_test, then after uploading the sketch, the contents would be accessible at:

http://goluino.local/sd/yun_test

#include <Bridge.h>
#include <YunServer.h>
#include <YunClient.h>

YunServer server;

void setup() {
  // put your setup code here, to run once:
  Bridge.begin();
  server.listenOnLocalhost();
  server.begin();

}

void loop() {
  // put your main code here, to run repeatedly:
  YunClient client = server.accept();

  if(client){
    String cmd = client.readString();
    cmd.trim();
    if(cmd == "temperature"){
      client.print(cmd);
    }
    client.stop();
  }
  delay(50);
}