linux cli request/response to arduino via serial

Hi. I've faced an issue with serial interaction between arduino nano and tp-link 703N (openwrt firmware).
I want to send request to arduino and receive response with temperature value based on dht11 measurement.

When i send request
echo 1 > /dev/ttyUSB0

I expect to receive one response but arduino responds with dozens values.
serial.available() value increases after each loop of the code that is why i get infinite loop of responses from arduino.

There is no such problem when i test sketch on PC.

My sketch below:

#include "DHT.h"

#define DHTPIN 10
byte ledPin =  6;
byte state = LOW;
int incomingData = 0;


#define DHTTYPE DHT11   // DHT 11 

DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(9600);
  Serial.println("serial init"); // debug string 
  pinMode(ledPin, OUTPUT); 
  dht.begin();
}

void loop() {
  int t = dht.readTemperature();
  int g = Serial.available();
  Serial.println(g);
  
  if (Serial.available() >0){
    delay(100);
    incomingData = Serial.read();      
    Serial.flush();
    delay(200);
 
   digitalWrite(ledPin, HIGH);
   delay(1500);
   digitalWrite(ledPin, LOW);

   Serial.println(t);
   delay(1000);
  }

}