Detach from screen session inside bash script

Question

I would like to run a bash scrpit while using a screen session, here is my script :

#!/bin/bash
for i in 1 5 18 20
do
screen -S output_${i}
./run_my_program
screen -d

The problem is that the screen session does not detach using screen -d (but detach with the keyboard shortcut ctrl-a d), any suggestion ? Thanks.

That also probably doesn't start the ./run_my_program within the screen, but waits for the first screen to return? Do you mean you want to start a detached screen session with some command? — ilkkachu, Jul 27 '17 at 11:59
@ilkkachu actually it start the program but don't close the screen session. — liquid-snake, Jul 27 '17 at 12:03

Eric Renouf · Accepted Answer · 2017-07-27 11:59:25Z

3

You don't have to "enter" the screen session to get it to run, just use -dm and it will start the session in detached mode:

for i in i 5 18 20; do
    screen -dm -S "output_$i" ./run_my_program
done

answered Jul 27 '17 at 11:59

Eric Renouf

13.9k43353

Thanks for your help, "output_${i}" is the name of my screen session write. – liquid-snake Jul 27 '17 at 12:03
@liquid-snake right, the -S argument names the session – Eric Renouf Jul 27 '17 at 12:04
What to do if I need to add an extra command before running my program, like export OMP_NUM_THREADS=1 && ./run_my_program ? – liquid-snake Jul 27 '17 at 12:05
@liquid-snake screen will inherit values from the parent, so you could always set/update the OMP_NUM_THREADS variable prior to launching, or if the script could take that as an argument, you could pass it that way, or you could run a shell to set the variable for you: screen ... sh -c "OMP_NUM_THREADS=1 ./run_my_program" – Eric Renouf Jul 27 '17 at 12:15
Thanks, it's working fine now, as you suggest I just run OMP_NUM_THREADS=1 befor the screen -dm -S ...... Thanks again Eric. – liquid-snake Jul 27 '17 at 13:00

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