Sending POST requests to ThingSpeak channel from Arduino YUN

env_station.ino

#include <Bridge.h>
#include <Console.h>
#include <Process.h>
#include <DHT.h>

DHT             dht;


#define Vref                 4.95
#define ARRAY_SIZE           4
#define DHTPIN               7

void setup() {
  Serial.begin(9600);
  Bridge.begin();
  Console.begin(); 
  dht = DHT(DHTPIN,DHT22);
  
};

void postToThingSpeak(String key, float value[]) {
  Process p;
  String cmd = "curl --data \"key="+key;
  for (int i=0;i<ARRAY_SIZE;i++) {
    cmd = cmd + "&field"+ (i+1) + "=" + value[i];
  }
  cmd = cmd + "\" http://api.thingspeak.com/update";
  p.runShellCommand(cmd);
  Console.println(cmd);
  p.close();
}
 
void loop() {
  float vol[ARRAY_SIZE];
  int sensorValue = analogRead(A0);
  int sensorValue2 = analogRead(A1);
  vol[0]=(float)sensorValue/1023*Vref;
  vol[1]=(float)sensorValue2/1023*Vref;
  vol[2] = dht.readTemperature();
  vol[3] = dht.readHumidity();
  postToThingSpeak("XXXXXXXX",vol);
  delay(2*60000);
}
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