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Old 07-29-2007, 03:50 PM   #1
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scripts with screen

i have started using the "screen" utility to launch processes that i need to dis- and re-connect to.

but i also need to stop and start these screen sessions with crontab (i.e. on a schedule)

this is the command i use to start a rtorrent screen session:
screen -d -m rtorrent

currently, i then use this to end it:
screen -r -X quit

however, the proper way to exit rtorrent is by pressing Control-A (key combo) and then the "q" key.

HOW CAN I SCRIPT THIS??!??!?? i am going insane!
so far, i know i need to use the "-X stuff ...." option, but i do not know how to pass in a control key combo sequence!

i have tried this, unsuccessfully:
screen -r -X stuff ^aq

this is within a bash shell session, so alternatively, if anyone can tell me how to script sending a control key combo, this may help...

please, anyone that can help me... you're my only hope!


Old 07-29-2007, 04:11 PM   #2
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Distribution: CentOS 6.5 OpenSuSE 12.3
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You can assign the value of ctrl-A in its octal representation to a shell variable, by means of the echo command and then use it in the command line. From man page of echo:
If -e is in effect, the following sequences are recognized:
\0NNN the character whose ASCII code is NNN (octal)
so the command substitution
$(echo -e '\0001')
where 001 is the octal code for Ctrl-A should give the desired value inside scripts or crontab entries.
Old 08-18-2007, 08:20 PM   #3
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Hey, I've been trying to do this also. Actually I'm just trying to use aliases to do some quick gameserver startup/exiting. I've got remote access to my dedicated server that is running CentOS, and I connect to it from my Windows client using PuTTY.

Currently I have these aliases:

alias bf2s='screen -S bf2screen;'
alias bf2run='cd /home/bf2user/gamecreate/bf2/; /bin/bash ./ +dedicated +lowPriority'
alias bf2show='screen -r bf2screen'

And what I do to start up the server is:

- I type bf2s, which opens the blank screen.
- Inside the screen I type bf2run, which starts the gameserver inside the screen session.
- Then I do a Ctrl-A, Ctrl-D to leave the screen.
- If I ever want to view the status I type bf2show, and do another Ctrl-A, Ctrl-D to leave the screen again.
- To shutdown this gameserver I either have to kill the screen and server processes manually by their PID, or I have to type bf2show, and then type exit, to close the screen session containing the game server.

What I'd like to do is:

- Have an alias (or a script that could be called by an alias) that would start up the server inside a screen using only one command.
- Have an alias (or a script that could be called by an alias) that would shutdown the server and the screen using only one command.

I've tried a number of things including piping and using < and > to send commands to the screen from a single prompt with no luck.

Can anyone give me a clue here? I've taken a basic linux class and am taking an Admin and Install linux class this coming semester, but this is beyond my knowledge.

Many thanks for any help!

- Matt
Old 08-19-2007, 06:22 AM   #4
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# Start screen session `rtorrent'
screen -S RTORRENT -d -m rtorrent
# Stop screen session `rtorrent'
screen -S RTORRENT -p 0 -X stuff ^Aq # Enter literal `^A' in bash by pressing CTRL-V followed by CTRL-A
# Alternative notations for ^A:
screen -S RTORRENT -p 0 -X stuff $'\001q' # $'\001' is octal notation for CTRL-A
screen -S RTORRENT -p 0 -X stuff $'\cAq' # $'\cx' is bash notation for a control-x character

If the current directory if import for, put this line at the begin of
cd "$(dirname "$(which "$0")")" # Go to script directory
See also:
This allows passing a single command to screen:
# Start screen session `bf2screen'
screen -S BF2SCREEN -d -m /home/bf2user/gamecreate/bf2/ +dedicated +lowPriority
# Stop screen session `bf2screen'
screen -S BF2SCREEN -p 0 -X stuff $'\cC'
See also:

Freddy Vulto

Last edited by fvu; 08-19-2007 at 09:49 AM.
Old 08-19-2007, 11:08 PM   #5
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Thanks a lot for the lead. I'll play around with that code for a bit.


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