Since Uno and Mega has no Serial, replace Serial with Console at Bridge Sample IDE code

/*
  WiFi Status

 This sketch runs a script called "pretty-wifi-info.lua"
 installed on your Yún in folder /usr/bin.
 It prints information about the status of your wifi connection.

 It uses Serial to print, so you need to connect your Yún to your
 computer using a USB cable and select the appropriate port from
 the Port menu

 created  18 June 2013
 By Federico Fissore

 This example code is in the public domain.

 http://www.arduino.cc/en/Tutorial/YunWiFiStatus

 To see the Console, pick your Yún's name and IP address in the Port menu
 then open the Port Monitor. You can also see it by opening a terminal window
 and typing
 ssh root@ yourYunsName.local 'telnet localhost 6571'
 then pressing enter. When prompted for the password, enter it.

 */
#include <Console.h>
#include <Process.h>

void setup() {
  //Serial.begin(9600);  // initialize serial communication
  //while (!Serial);     // do nothing until the serial monitor is opened
  //Serial.println("Starting bridge...\n");
  pinMode(13, OUTPUT);
  digitalWrite(13, LOW);
  Bridge.begin();  // make contact with the linux processor
  digitalWrite(13, HIGH);  // Led on pin 13 turns on when the bridge is ready
  Console.begin();
  while (!Console) {
    ; // wait for Console port to connect.
  }
  Console.println("Starting bridge...\n");
  delay(2000);  // wait 2 seconds
}

void loop() {
  Process wifiCheck;  // initialize a new process

  wifiCheck.runShellCommand("/usr/bin/pretty-wifi-info.lua");  // command you want to run

  // while there's any characters coming back from the
  // process, print them to the serial monitor:
  while (wifiCheck.available() > 0) {
    char c = wifiCheck.read();
    //Serial.print(c);
    Console.print(c);
  }

  //Serial.println();
  Console.println();
  delay(5000);
}