What is GNU Screen?
It's a program to view multiple virtual screens within one terminal window. If you remember DESQview for DOS, it's sort of like DESQview for Unix.
What is GNU Screen? Great!
Erm, a slightly more useful answer: it allows you to run multiple console applications, or commands, in one terminal. Kind of like a tabbed terminal emulator. In fact, that's exactly what it is (just not done with the regular GUI toolkits)
Why is it so great? Simple, you can run a program in a screen session (Run screen
and it runs your default shell, run screen myapp
and it runs myapp in the session), hit ctrl+a
(the screen control sequence) and then press d
(ctrl+a,d
) to detach.
The program keeps running in the background, but, unlike doing mycmd &
, you can run screen -r
to reattach the session, and everything is as you left it. You can send input to the command, if it's a curses UI, everything still works just like if it were a "real" terminal.
It's very popular with console IRC clients - you can run (say) screen irssi
and reattach the session from anywhere you can SSH from.
A few useful commands:
ctrl+a, c
to make a new virtual terminal (or "window") in the sessionctrl+a, n
andctrl+a, p
to cycle through multiple windowsctrl+a, 1
to select window 1,ctrl+a, 4
to select window 4 and so onctrl+a, ctrl+a
to flick between the last two active windowsctrl+a, shift+a
(upper-case a) allows you to rename the current windowctrl+a, "
(for me, that's shift+2 - the quote mark) lists windows, you can use the arrows and select one. Also useful with the "tab bar" setting I'll list in a second
A few other useful things I've stumbled across:
- Use the
-U
flag when you launch screen so it supports Unicode (for example,screen -xU
) - The
-x
flag allows you to reattach the same session multiple times. (-r
disconnects existing connections) You can do interesting stuff with the status bar. I have my setup to display
[ hostname ][ 0-$ bash (1*$ irssi) ][16/09 9:32]
(Running on hostname, it has two windows. This is set by the hardstatus lines in my .screenrc (at the end of the answer)startup_message off vbell off hardstatus alwayslastline hardstatus string '%{gk}[ %{G}%H %{g}][%= %{wk}%?%-Lw%?%{=b kR}(%{W}%n*%f %t%?(%u)%?%{=b kR})%{= kw}%?%+Lw%?%?%= %{g}]%{=y C}[%d/%m %c]%{W}'