Any session that I start with "-d -m" doesn't accept "-X stuff [...]" commands unless I've attached to the screen at least once. There is no error message, the commands just do not get through.
The problem is that I start the session from a cron job and am unable to attach to the screen from within cron.
Steps to repeat
$ screen -m -d -S mydaemon bash
$ screen -S mydaemon -X stuff "`printf "exit\\r"`"
$ screen -ls
32456.mydaemon (Detached)
$ screen -r -S mydaemon
$ ^a d
$ screen -S mydaemon -X stuff "`printf "exit\\r"`"
$ screen -ls
No Sockets found in /var/run/screen/S-user
^a d indicates pressing Ctrl+a then pressing d.
Versions
CentOS release 5.5 (Final)
Screen version 4.00.03 (FAU) 23-Oct-06
Edit: The best answer to this question is this other SO answer. I leave my kludgey solution here, anyway, in case it inspires a solution to a similar problem.
A possible workaround is to use a second, already running and detached screen session to start the screen session to which you want to send the "stuff" command in attached mode, and then send that screen session a detach command and then the stuff command.
$ screen -dmS spawner
$ screen -S spawner -X screen screen -dR mydaemon
$ sleep 1 # may be necessary
$ screen -S mydaemon -X detach
$ screen -S mydaemon -X stuff "whatever"
(Note: the doubled "screen" is not a typo!) You are still left with an unstuffable screen session (spawner) but if the resources it takes are important you can always just use "kill -TERM ..." or its ilk to terminate it (or have it automatically exit after a certain amount of time by starting it with something like
$ screen -dmS spawner bash -c "sleep 60"
or similar).
Have you considered using tmux instead? It is much more suitable for non-interactive tasks.
Thanks for Ron Kaminsky.
I found another way to kill 'spawner' screen
$ screen -dmS spawner
$ screen -S spawner -X screen screen -dR mydaemon
$ sleep 1 # may be necessary
$ screen -S mydaemon -X detach
and add below line
$ screen -S mydaemon -X screen screen -S spawner -dR
$ sleep 1 # may be necessary
$ screen -S spawner -X detach
$ screen -S spawner -X kill
screen -d -m /bin/bash "test.sh"
screen (detached) (mobile) (shell) "What to execute"
$ screen -d -m /bin/bash "test.sh"
$ screen -li
There is a screen on:
8540..Satelite (10/17/2013 04:53:22 AM) (Detached)
1 Socket in /var/run/screen/S-matt.
Using the .screenrc file, you can set things to start;
screen -t <title> <window position> <command>
So, if you wanted to start top in window 7, you'd do
screen -t window7top 7 top
Related
I want to create a small startup script that does multiple things in a row in a screen.
The script starts a named, detached screen (screen -S discordbot -d -m works)
The user inside the script is changed (Neither screen -S discordbot -X "su discordbot", screen -S discordbot -X su discordbot, nor screen -S discordbot -d -m bash -c "su discordbot;" seems to work, or at least subsqeuent commands are not executed).
A cd folder change is exectuded.
A java jar or other script is started.
As I run multiple bots, the script needs to be able to do this in slight variation multiple times in a row. Any pointers on how this could be done?
The screen session that you start up will exit as soon as the process that you started exits.
This works, for instance:
$ screen -S discordbot -d -m bash
$ screen -ls
There is a screen on:
2948.discordbot (Detached)
1 Socket in <...>
As does this:
$ screen -S discordbot -d -m bin/discordbot.sh
Where bin/discordbot.sh looks like this:
#!/bin/sh
echo "Sleeping..."
sleep 10
/bin/echo -n "Hit enter to finish this script: "
read
The last two lines to prevent the screen from exiting prematurely. The other various things you want to do within that startup script should also work, assuming that you do this as root so that the su will work without prompting.
Was wondering how I can start up a command such as:
while :; do ./myCommand; done;
But instead of doing the usual
screen -S nameOfMyScreen
Then the command
while :; do ./myCommand; done;
Then detach the screen
^a ^d (Control "a" the control "d"
I would like it to start and detach. Thanks!
screen -d -m sh -c "while :; do ./myCommand; done;"
Explanation:
-d -m starts screen in detached mode (create session but don't attach to it)
sh -c commandline starts a shell which executes the given command line (necessary, since you are using the while builtin).
From screen -h, these look useful:
-dmS name Start as daemon: Screen session in detached mode.
-X Execute <cmd> as a screen command in the specified session.
I haven't done this myself, but that's where I'd start.
Update:
The top of the help also says
Use: path/to/screen [-opts] [cmd [args]]
so the -X switch may be to execute a screen command as opposed to a shell command. You might just be able to put your command after the -dmS <name> without any -X switch.
so I'm trying to use this command:
export DISPLAY=:1; /usr/bin/xterm -hold -e /path/to/shscript
Where shscript is:
#!/bin/bash
echo "Restarting ... $(date)" >> /var/log/mw2.txt
if screen -ls | grep -q 'test'; then
screen -X -S test quit
sleep 1000
screen -d -m -S test wine iw4m.exe -dedicated -console +dw_licensefile license.dat +set net_port "28960" +set party_maxplayers 18 +exec server.cfg +map_rotate +set fs_game "mods/tsd"
else
screen -d -m -S test wine iw4m.exe -dedicated -console +dw_licensefile license.dat +set net_port "28960" +set party_maxplayers 18 +exec server.cfg +map_rotate +set fs_game "mods/tsd"
fi
So I want to launch a new xterm window and it to run a shell script.
But whatever shell script I try to use, it doesn't run it. It just goes blank. All other commands work, but when I put a shell script in it, it just goes blank and does nothing. I can't find a solution for this, please help, thank you.
I get this with set -x:
++ date
+ echo 'Restarting ... (date)'
+ grep -q test
+ screen -ls
+ screen -d -m -S test -wine iw4m etc...
I think you get exactly what you have asked for...
From screen's man page:
-d -m Start screen in "detached" mode. This creates a new session but
doesn't attach to it. This is useful for system startup
scripts.
On the other hand you use -hold for xterm:
-hold Turn on the hold resource, i.e., xterm will not immediately
destroy its window when the shell command completes. It will
wait until you use the window manager to destroy/kill the win‐
dow, or if you use the menu entries that send a signal, e.g.,
HUP or KILL.
And that's exactly what you see. xterm starts, executes screen which runs, but you don't see the output as screen does not attach to the virtual terminal. Since screen has detached the shell script exits and xterm holds the window for you to destroy it at your leisure.
I bet that if in another xterm you attach to the session with screen -S test you'll see the output.
Yep. It was the wine command failing. I changed some stuff, and it works now. I had to put cd /home/MW2 in the script for it to be able to run the iw4m.exe, then screen -S etc.
I'm writing a Linux shell script in which I need to start a new screen session, run a node.js server in the screen, then detach from the screen so that my server runs in the background.
Right now, these are the commands I run manually to do this:
screen
node server.js
[detach screen]
However, I need a way to automate this via the script, and if I just use the above commands in a shell script, it creates the screen and gets stuck there. How can I pass the "node server.js" command to the screen command?
EDIT:
Based on the suggested answer I have a script that works, except that I need to manually create a screen and detach from it before I run it. I tried adding screen -d -m as the first line to create a detached screen, but the script hangs after that line.
tempfile=$(mktemp)
indices=`tail -1 debug.log`
cat > $tempfile <<EOF
node server $indices
EOF
screen -X readbuf $tempfile
screen -X paste .
rm -f $tempfile
How can I create and detach a screen with the script?
This didn't work either:
screen
screen -d
It is as simple as this:
screen -md node server.js
This requires the command to run as a service (as it does), otherwise the screen stops immediately.
To optionally also set a name for the session (e.g. "session-name"):
screen -mdS session-name node server.js
You can then attach to the screen with:
screen -rd session-name
If you want to redirect all output to a file, you can do like this:
screen -mdS session-name bash -c 'node server.js &> output.log'
You can then monitor the output with e.g.:
tail -f output.log
You can list your running screens with:
screen -ls
or
screen -list
Example: Start a Python3 web server in a detached screen
Start a Python3 web server listening on port 8000 that serves files in the current directory, in a named
detached screen:
screen -mdS my-web-server python3 -mhttp.server
Or, with logging to a file:
screen -mdS my-web-server bash -c 'python3 -mhttp.server &> output.log'
For Python 2.x it looks like this:
screen -mdS my-web-server bash -c 'python -mSimpleHTTPServer &> output.log'
EDIT: Try this:
tempfile=$(mktemp)
cat > $tempfile <<EOF
node server.js
EOF
screen -S SessionName -X readbuf $tempfile; screen -RdS SessionName
screen -X paste .
rm -f $tempfile
It should create the temp file, create a screen called SessionName and runs the commands, then delete the temp file. Let me know if that works.
I created a screen "myscreen" in linux and it stopped responding abruptly. I closed the terminal and tried to reopen it. "screen -ls" shows that the screen is Attached. I tried the following commands but nothing responds.
screen -r myscreen
screen -D myscreen
screen -D -RR myscreen
screen -X -S myscreen quit
Any help to reattach to the screen or to kill the screen is very much appreciated.
screen -X -S SCREENID kill
alternatively, you can use the following command
screen -S SCREENNAME -p 0 -X quit
You can view the list of the screen sessions by executing screen -ls
Create screen from Terminal:
screen -S <screen_name>
To see list of screens:
<screen -ls> or <screen -list>
To go to particular screen:
<screen -x screen_name>
<screen -r screen_name>
Inside screen
To Terminate screen:
give ctrl+d screen will get terminated
To Detach screen:
give <ctrl+ad>or <screen -d >screen will get detached
To reattach screen:
screen -x <screen_name> or screen -r <screen_name>
To kill a screen from Terminal:
<screen -X -S screen_name quit>
or
<screen -X -S screen_name kill>
You can use screen_name or process_id to execute commands.
This worked for me very well. Get the screen id via:
screen -r
or
screen -ls
then kill the screen: kill -9 <screenID>
it now becomes a dead screen,
then wipe it out with: screen -wipe
To kill a detached screen use this from the terminal:
screen -X -S "SCEEN_NAME" quit
If you are attached, then use (from the terminal and inside the screen):
exit
From Screen User's Manual ;
screen -d -r "screenName"
Reattach a session and if necessary detach it first
You could create a function to kill all existing sessions. take a look at Kill all detached screen sessions
to list all active sessions use
screen -r
when listed, select with your mouse the session you are interested in and paste it. like this
screen -r
Suppose your screen id has a pattern. Then you can use the following code to kill all the attached screen at once.
result=$(screen -ls | grep 'pattern_of_screen_id' -o)
for i in $result;
do
`screen -X -S $i quit`;
done
i usually don't name my screen instances, so this might not be useful, but did you try screen -r without the 'myscreen' part? usually for me, screen -r will show the PIDs of each screen then i can reattach with screen -d -r <PID>
You can find the process id of the attached running screen.
I found it same as the session id which you can get by command:
screen -ls
And you can use following command to kill that process:
kill [sessionId] or sudo kill [sessionId]
None of the screen commands were killing or reattaching the screen for me. Any screen command would just hang. I found another approach.
Each running screen has a file associated with it in:
/var/run/screen/S-{user_name}
The files in that folder will match the names of the screens when running the screen -list. If you delete the file, it kills the associated running screen (detached or attached).
For result find: Click Here
Screen is a full-screen window manager that multiplexes a physical terminal between several processes, typically interactive shells. There is a scrollback history buffer for each virtual terminal and a copy-and-paste mechanism that allows the user to move text regions between windows.