Question

I have a GNU screen named demo, I want to send commands to it. How do I do this?

screen -S demo -X /home/aa/scripts/outputs.sh

yeilds No screen session found.

and doing screen -ls shows that it isn’t running.

Answer 1

If the Screen session isn’t running, you won’t be able to send things to it. Start it first.

Once you’ve got a session, you need to distinguish between Screen commands and keyboard input. screen -X expects a Screen command. The stuff command sends input, and if you want to run that program from a shell prompt, you’ll have to pass a newline as well.

screen -S demo -X stuff '/home/aa/scripts/outputs.sh
'

Note that this may be the wrong approach. Are you sure you want to type into whatever is active in that session? To direct the input at a particular window, use

screen -S demo -p 1 -X stuff '/home/aa/scripts/outputs.sh
'

where 1 is the window number (you can use its title instead).

To start a new window in that session, use the screen command instead. (That’s the screen Screen command, not the screen shell command.)

screen -S demo -p 1 -X screen '/home/aa/scripts/outputs.sh'