Running a command that includes an STDIN redirect with screen

Question

Using the Gradle SSH plugin I deploy a .jar file to another machine.

I then would like to run that jar in a detached screen session. This wouldn't be a problem if the application did not require input on STDIN, running screen -dmS screen-name java -jar my.jar.

I tried to provide the input (beside others approaches) in the following way using a here-string, yet I did not get any of them to work:

screen -dmS screen-name java -jar my.jar <<< "firstInputLine
SecondInputLine
"

Can anyone point me in the right direction? Thanks!

Answer 1

I currently solved this by first creating the detached screen session an then, with a second screen call, forwarding the input using screen's stuff command, not using a here-string anymore:

screen -dmS screen-name java -jar my.jar && 
screen -S screen-name -p 0 -X stuff "firstInputLine^MsecondInputLine^M"

(^M is interpreted as ENTER)

Answer 2

I think your problem is that you are piping the input to the screen command and not actually to the java process. I would do it the following way:

1. create a file with your input, something along the lines of echo "foo" > input.txt
2. scp that file to the machine
3. run the screen command and make the java process either read the file directly (if that program can do that) or pipe it properly by running a bash command instead of the java command directly. Something along the lines of screen -dmS screen-name bash \"cat input.txt | java -jar ...\"

Disclaimer: the above escaping is just approximate to get my point accorss ;-)