php - Screen -X isn't working ("No screen found")

Question

I have this php code:

echo shell_exec('sh /backups/turnon.sh');

The /backups/turnon.sh code is:

screen -X 'cd /ftb; java -Xms2048m -Xmx2048m -jar mcpc.jar'

However, that outputs to the website:

No screen session found.

However if I open PuTTY and I do screen -x I can load the screen with no issue. What am I doing wrong.

Answer 1

The man page for screen specifically states:

-x   Attach to a not detached screen session. (Multi display mode).
-X   Send the specified command to a running screen session.

The error message you're getting says that there's no existing screen process running to attach to. Something is different between your PuTTY login environment and the environment in which the script is trying to run, possibly that you have a screen session running as your PuTTY login user but none running as the user running the script.