Using screen in bash script

Question

I'm running a game server on a remote server where I use a detached screen instance to leave it running. I'm now creating a script that can be used to shut down the server, back up all the vital files and start it up again, however I'm having a few difficulties with dealing with the screen.

I assumed that I could just switch into the detached screen in the script (after the server had already been shut down) by calling screen -r in the script. But that doesn't seem to work because if I run the script from outside screen it just launches the server in that session.

screen -r
cd ~/servers/StarMade/
sh StarMade-dedicated-server-linux.sh
screen -d

This is what I thought would do the trick but it doesn't. Maybe somebody can help me out here. I'm not a bash expert. In fact this is propably my first bash script that doesn't include "Hello World". Thanks.

Just take into account "Supervisor", the right tool for your needs — Robert
– Robert, Commented Jan 2, 2014 at 10:49
Might be a bit overkill for the ONE script that I want to run. But if my needs become more complex I'll be sure to check it out. Thanks. — AreusAstarte
– AreusAstarte, Commented Jan 2, 2014 at 10:58

Guntram Blohm · Accepted Answer · 2014-01-02 10:38:21Z

5

Your script, as in your example, will get executed by your sell, not the one in the screen. You need to tell the running screen to read a file and execute it - that's what the -X option is for.

Try

tempfile=$(mktemp)
cat > $tempfile <<EOF
cd ~/servers/StarMade/
sh StarMade-dedicated-server-linux.sh
EOF
screen -X readbuf $tempfile
screen -X paste .
rm -f $tempfile

You can leave screen running in a 2nd terminal session to see what happens.

answered Jan 2, 2014 at 10:38

Guntram Blohm

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2 Comments

AreusAstarte Over a year ago

Hey, thanks for the quick reply. A few questions. First, what is that EOF thing you're doing there? And secondly screen -X attaches a command to a running screen session, right? Don't I need to specify which one? Lastly when I'm done with this, what do I need to change in my script? Or from where do I run it now?

Guntram Blohm Over a year ago

The EOF thing is a here document, which means everything between the <<EOF and the EOF will be put into the standard input of cat, which writes it to the temp file. Second, -X will select the same screen that -r does - but you can combine -X with -r to select a specific one. Third, you replace your complete script with mine, and run it on the computer where screen is running.

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