How to upload one program into several Arduinos at once? I am trying to upload a single program to a number of Arduinos one by one. But it is time consuming. So I would like to know if there is any way to upload the code at once to multiple Arduinos.

I have tried as follows:

3 Arduino with all the Rx, Reset, Vcc, Gnd line connected to each other. Only pin left is Tx line. So I just connect the Tx line of one arduino and program it and so on.

Is there any other way?
Are you programming them for the first time or doing a update?

If is the first programming, I cant see another way. 

Otherwise, If is a update and your Arduino have a Wifi module you could try something like an update on the air, where you put your new firmware in a server for example and all devices updates yourself automatically or by a command.

Google for Arduino OTA (on the air) you will get a lot of source code and examples of doing that.