Quick guide to GNU screen

Start a screen session

$screen

Detach from the screen session

Ctrl+a d
(Hit Ctrl+a quickly followed by hitting just d)

List current screen sessions

$ screen -ls
There is a screen on:
1119.pts-0.acer11 (Detached)
1 Socket in /run/screens/S-brm.

screen -list does the same thing.

Attach to this screen session

$screen - r

Attach to an already attached screen. That is , if the session is already attached by someone else or somewhere else. The other person will able to see what you type on the terminal, a nice way to share screen.

$screen -x

Terminate the screen session

(Ctrl+a k)
(Hit Ctrl+a quickly followed by hitting k)

Alternate ways to terminate screen session is Ctrl+d or exit as you would on a shell session. But only Ctrl+a k asks for confirmation like this:

 kill this window [y/n]

After terminating a screen session, you should see something like this, you are taken back to the prompt where you started or attached the session.

[screen is terminating]
$

Now there are no screen session.

$ screen -ls
No Sockets found in /run/screens/S-brm.

Attach to a session when there are multiple sessions There are three sessions here:

$screen -ls
There are screens on:
1209.pts-0.acer11 (Detached)
1205.pts-0.acer11 (Detached)
1202.pts-0.acer11 (Detached)
3 Sockets in /run/screens/S-brm.

To attach to the middle one 1205.pts-0.acer11 (Detached):

$screen -r 1205.pts-0.acer11
or just
$screen -r 1205

If the session is already attached by someone else, somewhere

$screen -x 1205

To name a session while starting for easy reference

$screen -S SessionName

SessionName given will now appear in screen -ls output

To change the window title

$screen -t Newtitle

I find this useful to see where I am.

How I can tell I am in a screen session and which session?

$ echo $STY
1209.pts-0.acer11

Compare the output from screen -ls. If you are not attached to any screen session, you get a blank output.