SIM800 +Pushingbox +AT commands data format question

line:
char http_cmd = “GET /pushingbox?devid=v0B1A48DD9C0DB&sensor1=”+a"&sensor2="+b" HTTP/1.1\r\nHost: api.pushingbox.com\r\n\r\n";

is posting data to pushingbox and google, but gets error:
initializer fails to determine size of ‘http_cmd’

sensor values are :
char a= 1;
char b= 2;

in what format they must be to be correct ?

How can I put dynamic values in GET line ?

#include <gprs.h>
#include <SoftwareSerial.h>
GPRS gprs;
void setup() {
  Serial.begin(9600);   }

void loop() {   

  Serial.begin(9600);
  while(!Serial);
  Serial.println("GPRS - HTTP Connection Test...");  
  gprs.preInit();
  while(0 != gprs.init()) {
     delay(1000);
     Serial.println("init error");
  }  
  while(!gprs.join("cmnet")) {  //change "cmnet" to your own APN
      Serial.println("gprs join network error");
      delay(2000);
  }
  // successful DHCP
  Serial.print("IP Address is ");
  Serial.println(gprs.getIPAddress());
  
  Serial.println("Init success, start to connect box...");
  
  if(0 == gprs.connectTCP("api.pushingbox.com", 80)) {
      Serial.println("connect www success");
  }else{
      Serial.println("connect error");
      while(1);
  }

char a= 1;
char b= 2;

char http_cmd[] = "GET /pushingbox?devid=v0B1A48DD9C0DB&sensor1="+a"&sensor2="+b" HTTP/1.1\r\nHost: api.pushingbox.com\r\n\r\n";    

char buffer[512];
 
  Serial.println("waiting to fetch...");
  if(0 == gprs.sendTCPData(http_cmd))
  {      
   // gprs.serialDebug();
  }
  Serial.println("5..");  
  delay(51000);
  
 gprs.closeTCP();
 //gprs.shutTCP();
 Serial.println("close");  
}

http://www.cplusplus.com/reference/cstring/strcat/

.

when i add 2 strings then i get error:

invalid operands of types 'const char*' and 'const char [40]' to binary 'operator+'

when i add 2 strings then i get error: invalid operands of types 'const char*' and 'const char [40]' to binary 'operator+'

There is no "+" in strcat. Did you look at the reference and try to use that function your code?

OK now its fine and working ... sending data from 2 arduino analog inputs to google sheets via sim800 :)

// SENSOR 1 - char
String str1 = String(analogRead(A0), DEC);
int str1_len = str1.length() + 1; 
char sen1_char[str1_len];
str1.toCharArray(sen1_char, str1_len);

// SENSOR 2 - char
String str2 = String(analogRead(A0), DEC);
int str2_len = str2.length() + 1; 
char sen2_char[str2_len];
str2.toCharArray(sen2_char, str2_len);


Serial.println(sen1_char);
 char str[110];
  strcpy (str,"GET /pushingbox?devid=v0B1A48DD9C0DB&sensor1=");
  strcat (str,sen1_char);
  strcat (str,"&sensor2=");
  strcat (str,sen2_char);
 strcat (str," HTTP/1.1\r\nHost: api.pushingbox.com\r\n\r\n");
  puts (str);

 Serial.println(str);  
  
  if(0 == gprs.sendTCPData(str))