Screen
Screen is a window manager that allows you to have multiple shells running in one terminal window. When screen is called, it creates a new shell so that you can use the program independently of the currently running shell. And at any time, you can detach, resume or switch the shells without terminating the running programs. For more information, please check the screen user's manual https://www.gnu.org/software/screen/manual/screen.html.
Basic Usage
Here is the basic usage of screen. First, create a new session:
screen -S demo
We now switch to a new screen shell. This new session named demo and runs independently. To print the list of sessions, we can use:
screen -ls
There is a screen on:
22087.demo (04/18/2017 11:36:31 AM) (Attached)
1 Socket in /var/run/screen/S-ryli.
Sessions marked 'Attached' are running. Here we have one session named demo with id 22087. We can run any program in this new session, e.g., show the GPUs' information:
nvidia-smi -l
This program shows the GPUs' information every 5 seconds. We now detach this session without terminating the nvidia-smi program:
Control-a d
# hold down the 'Control' key, press and release the 'a' key, and then type 'd'
If we print the list of sessions again:
screen -ls
we can see the following:
There is a screen on:
22087.demo (04/18/2017 11:36:30 AM) (Detached)
1 Socket in /var/run/screen/S-ryli.
The demo session marked 'Detached' is running in the background and can be easily resumed by typing:
screen -r demo
The terminal will switch back to the demo session and the nvidia-smi program is still running. After we terminating the currently running nvidia-smi program by Control-c, we can kill the session:
exit
There is no session when we show the list:
screen -ls
No Sockets found in /var/run/screen/S-ryli.
Some Useful Commands
Here are some commonly used commands in screen.
List all the sessions
screen -ls
Create new session
screen -S #sessionname#
Resume a session
screen -r #sessionname/sessionid#
Detach from a session
Control+a d
Kill a running session
Control+a k
or
exit
Enter copy mode
Control+a [
Once we enter the copy mode, we can do the following things.
- Scroll forward one screen:
Control+f - Scroll back one screen :
Control+b - Move to beginning of session:
0 - Move to end of session:
$ - Exit:
exit