GNU Screen

Screen is a Unix tool that can be thought of as a window manager for the shells inside your terminal. It allows to handle several virtual consoles within a single terminal window.

Furthermore it can provide a persistent console when working remotely with ssh. If you use ssh to work remotely on a computer, you often want your processes to keep running even when you disconnect or loose the network connection. Screen allows to create persistent shells, which you can detach and re-attach any time, to continue your work where you left off (see the example below).

Alternatives: tmux or mosh

Main Commands

From the command-line

screen -S name    # start a new screen session with a given name
screen -ls        # list open screen sessions
screen -r name    # re-attach given screen session

From within a screen session

Ctrl-a d          # detach current screen session
Ctrl-a c          # create new window
Ctrl-a n / p      # switch to next/previous window
Ctrl-a 3          # switch to window number 3
Ctrl-a Ctrl-a     # toggle between current and previous window
Ctrl-a S          # split display horizontally
Ctrl-a |          # split display vertically
Ctrl-a Q          # remove split displays
Ctrl-a Tab        # jump to next display region
Ctrl-a X          # remove current display region
Ctrl-a k          # kill current window
Ctrl-a x          # lock the screen
Ctrl-a ?          # display help with list of shortcut keys

The screen utility can be customized through ~/.screenrc.

Example: ssh + screen

ssh     # connect to the remote host
screen -S work                  # start a screen session on the remote host
./      # do you work, for instance by running computations
Ctrl-a d                        # detach the screen session, and close the ssh connection

When you later reconnect to that host, you can reconnect to that screen session, see what kind of output was produced while you were away, and continue your work

ssh     # reconnect
screen -r work                  # re-attach screen session