How do I clear previous values while using strcat() to add strings? Is there any other function to add strings into buffer and updating values as well.

This is the problem I am coping with while using strcat()



char temp[2] = "A";
char temp_end[2] = "a";
char buf_adc[20]="alok";
char buf_hum[20]="lok";
char buf_temp[20]="vjf";
char buf[100];
void setup() {
Serial.begin(115200);

}

void loop() {
  strcat(buf,buf_adc);
strcat(buf,temp);
strcat(buf,buf_hum);
strcat(buf,temp);
strcat(buf,buf_temp);
strcat(buf,temp_end);

Serial.println(buf);

}
strcat always concatenates to the end of the string. Instead, for your first strcat you should really be using strcpy, which copies one string over the top of the other - that is, it places it at the start of the string, effectively starting a new string.

However, unless you really need the data in a string for some specific reason, you don't need to build a string up - just print each part to serial separately with its own Serial.print function.