[SOLVED] how to start a screenlog from one command?

coolCAT · 03-08-2013, 08:51 PM

I am trying to start a screenlog from a shell script. The process is already running and I want to enable the screenlog just as my script starts then stop the screenlog at the end of my script.

I know I can screen into the task that is running and start the logging manually:
screen -r myTask
then
ctrl+a shift+h
then detach
ctrl+a ctrl+d

However I would like to get fancy!
I have tried all kinds of variations of the following without any luck.
screen -L -r myTask
screen -r myTask -X ^aa H ^aa ^ad

I see a lot of forums where people send commands into screen but I am not understanding the syntax for the command. I do not know what the ctrl+a would look like and what would the shift+h look like.

Process I am trying to start the screen log is started like this:
screen -h 1000 -d -m -S myTask
I can add a '-L' before the '-h' and it logs everything. However I would like to only log data during my script execution.

I feel like I am right there, but just not getting it. Any advise would be much appreciated.

shivaa · 03-08-2013, 09:51 PM

What's your ultimate purpose? Screen (see manual here) command is somewhat like nohup.
As much as I know, it's useful when you work remotely.

coolCAT · 03-09-2013, 05:10 PM

I use screen to start a process that controls multiple other tasks. I get a lot of ouput from the screen and would like to only capture the data when I run a script that enduse problems to test my process for failures. If I can get the screenlog started and stoppped without attaching to the session I would have everything I need to find the bugs in my code.

I have been reading the man & help pages as well as experiment with different options. I feel like I am fishing in the dark though.

theNbomr · 03-09-2013, 06:21 PM

I think you can specify the logfile name, start and stop the logging process by using the '-X' option plus an argument:

Code:

#
#  Start the screen session 
#
screen -S MYSCREEN

Then, from a different shell...

Code:

screen -S MYSCREEN/ -X logfile '/some/filespec'
screen -S MYSCREEN/ -X log on
#
# ... some time later...
#
screen -S MYSCREEN/ -X log off

--- rod.

coolCAT · 03-10-2013, 10:14 AM

@theNbomr,

Thanks! That is exactly what I was trying to do! You are awesome!

coolCAT · 03-18-2013, 02:53 PM

Quote:

Originally Posted by theNbomr

I think you can specify the logfile name, start and stop the logging process by using the '-X' option plus an argument:

Code:

#
#  Start the screen session 
#
screen -S MYSCREEN

Then, from a different shell...

Code:

screen -S MYSCREEN/ -X logfile '/some/filespec'
screen -S MYSCREEN/ -X log on
#
# ... some time later...
#
screen -S MYSCREEN/ -X log off

--- rod.

Rod,

I have found this actually only works if I have started a screenlog manually. If I have not started the screenlog manually then it is not working.

-- Josh

theNbomr · 03-18-2013, 03:56 PM

Not sure what you mean by 'started the screenlog manually'. It may be that you refer to the matter of launching screen in detached mode. When commanding a screen session that has been launched in detached mode, and has not ever been attached, you need to use the '-p 0' option:

Code:

screen -S MYSCREEN/ -p 0 -X logfile '/some/filespec'
screen -S MYSCREEN/ -p 0 -X log on
#
# ... some time later...
#
screen -S MYSCREEN/ -X log off

--- rod.

coolCAT · 03-21-2013, 10:17 AM

Quote:

Originally Posted by theNbomr

Not sure what you mean by 'started the screenlog manually'. It may be that you refer to the matter of launching screen in detached mode. When commanding a screen session that has been launched in detached mode, and has not ever been attached, you need to use the '-p 0' option:

Code:

screen -S MYSCREEN/ -p 0 -X logfile '/some/filespec'
screen -S MYSCREEN/ -p 0 -X log on
#
# ... some time later...
#
screen -S MYSCREEN/ -X log off

--- rod.

That is exactly what I needed! Thanks Rod, You saved me from a lot of pain.