Shell – How to write a shell script to run multiple command in different screen sessions

gnu-screenshell-scriptzsh

My goal is to write a zsh script in order to create multiple screen sessions and run separate commands on each of them. I would also like to check at the beginning of my script if there are any screens with running jobs and terminate all of them that sit idle. Furthermore, if possible I would like to have a way to record the stdout of the individual screen and get their ID number. So far I have tried the following:

### Script for running everything in screens ###
killall -15 screen ## We make sure that no screens are running for now
#bkg_array = ("TopJets" "BosonJets" "DiBoson" "TTbar")

screen -dmS "MYSCREEN"
screen -S "MYSCREEN" -p 0 -X stuff 'echo "The array has of elements."\n'

However, I cannot seem to send the keystroke for pressing Enter; how can I achieve that effect? Additionally without the -p option the command is not sent to the screen. After pressing Ctrl+V+Enter the characters ^M were pasted on the screen and it pressed enter in the screen session, but I have no idea why that worked.

Thanks for your help, feel free to point out any ambiguities.

Best Answer

I find that while screen doesn't interpret named characters such as \n, it does take care of octal escapes. So instead of stuff 'echo "The array has of elements."\n', you could use:

stuff 'echo "The array has of elements."'\012

Related Solutions

Killing multiple GNU screen sessions with the same name

If there are no other screen sessions running you can use the "hard" way and just kill them with killall screen.

If you want to be nice you can iterate over your list of screen sessions and kill them one after another:

# screen -S foo && screen -S foo
[detached]
[detached]
# screen -ls
There are screens on:                                                                                                                                                                                      
        8350.foo        (Detached)                                                                                                                                                                         
        8292.foo        (Detached)                                                                                                                                                                         
2 Sockets in /tmp/screens/S-joschi.                                                                                                                                                                        

# This is the interesting line. Just replace "foo" with the name of your session(s)
# for session in $(screen -ls | grep -o '[0-9]*\.foo'); do screen -S "${session}" -X quit; done
# screen -ls
No Sockets found in /tmp/screens/S-joschi.

Concatenate two screen sessions

As far as I am aware, this is not possible using screen, but you could use reptyr to reassign the program to a new terminal.

Here is some useful guidance on using reptyr:

Attach running process to new terminal -- you probably want to read this, it should help you assign the program to screen
Change process' controlling terminal

You could also look at using the slightly less complex grab.c.

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