esp8266/libraries/Bridge/examples/TimeCheck/TimeCheck.ino

/*
  Time Check

 Gets the time from Linux via Bridge then parses out hours,
 minutes and seconds for the Arduino using an Arduino Yún.

 created  27 May 2013
 modified 21 June 2013
 By Tom Igoe

 This example code is in the public domain.

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

 */


#include <Process.h>

Process date;                 // process used to get the date
int hours, minutes, seconds;  // for the results
int lastSecond = -1;          // need an impossible value for comparison

void setup() {
  Bridge.begin();        // initialize Bridge
  Serial.begin(9600);    // initialize serial

  while (!Serial);              // wait for Serial Monitor to open
  Serial.println("Time Check");  // Title of sketch

  // run an initial date process. Should return:
  // hh:mm:ss :
  if (!date.running()) {
    date.begin("date");
    date.addParameter("+%T");
    date.run();
  }
}

void loop() {

  if (lastSecond != seconds) { // if a second has passed
    // print the time:
    if (hours <= 9) Serial.print("0");    // adjust for 0-9
    Serial.print(hours);
    Serial.print(":");
    if (minutes <= 9) Serial.print("0");  // adjust for 0-9
    Serial.print(minutes);
    Serial.print(":");
    if (seconds <= 9) Serial.print("0");  // adjust for 0-9
    Serial.println(seconds);

    // restart the date process:
    if (!date.running()) {
      date.begin("date");
      date.addParameter("+%T");
      date.run();
    }
  }

  //if there's a result from the date process, parse it:
  while (date.available() > 0) {
    // get the result of the date process (should be hh:mm:ss):
    String timeString = date.readString();

    // find the colons:
    int firstColon = timeString.indexOf(":");
    int secondColon = timeString.lastIndexOf(":");

    // get the substrings for hour, minute second:
    String hourString = timeString.substring(0, firstColon);
    String minString = timeString.substring(firstColon + 1, secondColon);
    String secString = timeString.substring(secondColon + 1);

    // convert to ints,saving the previous second:
    hours = hourString.toInt();
    minutes = minString.toInt();
    lastSecond = seconds;          // save to do a time comparison
    seconds = secString.toInt();
  }

}