Linux Training : 9. screen


screen is a window manager for the console.

screen stays connected

Long running process should be run within screen so a lost connection will not stop the process. The user can detach from a running screen session at any time with ctrl-a d and the processes in that terminal will not stop. Later, run screen -ls to see running screens (open sockets in /var/run/screen/)

There is a screen on:
        15084.pts-1.sis-jpk     (Detached)
1 Socket in /var/run/screen/S-jkinney9.

and then reconnect with screen -r 15084 to pick up where you left off.
The Linux Journal article is a good walkthrough of how to use screen. While the default screenrc is adequate, this one can be put into ~/.screenrc and provides some nice indicators at the bottom

# This hardstatus line will be at the bottom of the screen
#hardstatus alwayslastline "%-Lw%{= BW}%50>%n%f* %t%-%+Lw%< %=%D %M %d %c"

# This hardstatus causes the gnome termnal top bar to blink "screen"
# and indicates which screen is active by shifting the "-" around. blinking is very ugly.
#hardstatus string '%{= kK}%-Lw%{= KW}%50>%n%f %t%{= kK}%+Lw%< %{=kG}%-= %d%M %c:%s%-'

# The caption line will be displayed at the bottom of the screen within the window
caption always "%?%{ Wk}%-Lw%?%{Rk}%n*%f %t%?(%u)%?%?%{Wk}%+Lw%? %{Rk}%=%c %{rk}%Y/%m/%d"

# The hardstatus line will be displayed in the gnome-terminal top bar
#hardstatus string "%{+b Rk}(%{-b g}$LOGNAME@%H%{+b R}) (%{-b g}%C %a%{+b R}) %{-b g} %n %t %h"

# defscrollback will set the number of lines in the scrollback buffer
defscrollback 1024
screen exercise

Use ssh to connect to the svn machine. Start a screen session. Run the following simple script that will display the time every 5 seconds.

while true; do echo -en $(date)"\r"; sleep 5s; done

Detach from the screen session and log out of the svn machine. Log back in and reattach to the screen session and verify the script is still running.
Stop the script with Ctrl-c