Is there alternative to Serial monitor?

Is there any standalone alternative to Arduino serial monitor?

I like gnu screen, but cat works OK, also. Make sure to use stty before calling cat though, like this:

stty -F /dev/ttyACM0 115200; cat /dev/ttyACM0

Assuming you have a baud rate of 115200 of course. You might get away without stty if you use the default rate.

For gnu screen, it's just

screen /dev/ttyACM0 115200

Thanks for reply.
I should correct myself - are there any cross-platform or windows alternatives?

Can you use Windows Command Prompt as Serial Monitor? If yes, how to do?

On older flavours of Windows you could use Hyperterminal to read/write a COM port. That's been dropped though, so on more recent versions you'd need to use a 3rd party alternative such as PuTTY.