Screen will not start. no clue why

Question

I have this script that runs every hour or so, and it is supposed to check to see if a minecraft server is running in a screen, and if its not, then it should start the server in the screen.

if ! screen -list | grep -q "mc"; then
        echo "starting"
        screen -dmS mc /home/mc/run_server.sh
fi

I am still new to Bash and i have been trying to debug this and have not come up with why it will not start.

Answer 1

It should work. What exactly doesn't start? Have you put it in a file?

#!/bin/bash
if ! screen -list | grep -q "mc"; then
    echo "starting"
    screen -dmS mc /home/mc/run_server.sh
else
    echo "minecraft server is already running!"
fi

Save it in, for example, your home directory as mc.sh file. Set executable permissions for it:

chmod +x mc.sh

And try to run it:

./mc.sh

The ! screen -list | grep -q "mc" condition works if there are no entries named "mc" found in screen -list (the command that lists all running sessions), so if there are NO "mc" screen sessions at the moment, it will show you a "starting" message and start a new screen session in which the run_server.sh will be ran.

Otherwise it will show "minecraft server is already running!" and do nothing.

If you have put it in a crontab and it doesn't work there, try to use every command with an absolute path.

0 * * * * /home/alandoyle/mc.sh

And replace every screen usage in script with a full path to screen (for example, /usr/bin/screen; you can determine your one using a which screen command)