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I have a Python script test.py that only contains: print('hi'). I want to run it in a screen so that the output of the screen is saved by script.

I use the following command to run test.py in a screen, it works fine:

screen -dm bash -c 'python test.py'

However, I haven't managed yet to find a way to use script to save the output of the screen. How can I do it?

I unsuccessfully tried:

  • script -c "screen -dm bash -c 'python test.py'" output.txt: the output file output.txt doesn't contain hi, but only:

    Script started on Fri 26 Aug 2016 01:04:59 PM EDT

Script done on Fri 26 Aug 2016 01:04:59 PM EDT

I use Ubuntu 14.04.4 LTS x64.

Documentation:

https://www.gnu.org/software/screen/manual/screen.html:

-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.

http://linux.about.com/library/cmd/blcmdl1_sh.htm :

-c string: If the -c option is present, then commands are read from string. If there are arguments after the string, they are assigned to the positional parameters, starting with $0.

script's man page:

-c, --command run command rather than interactive shell

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16

You can use the -L flag to create an automatic screenlog.0 file

eg

$ screen -dm -L sh -c 'echo hello'
$ cat screenlog.0 
hello

If you have a long running screen session that isn't being logged then you can turn on logging later

eg

$ screen -dm -S test sh -c 'while [ 1 ]; do date; sleep 1; done'

Now we can turn on logging

$ screen -S test -p 0 -X log

Allow some time to pass, because the logging is written in blocks, and...

$ cat screenlog.0
Fri Aug 26 13:25:49 EDT 2016
Fri Aug 26 13:25:50 EDT 2016
Fri Aug 26 13:25:51 EDT 2016
Fri Aug 26 13:25:52 EDT 2016
Fri Aug 26 13:25:53 EDT 2016
Fri Aug 26 13:25:54 EDT 2016
Fri Aug 26 13:25:55 EDT 2016
Fri Aug 26 13:25:56 EDT 2016
Fri Aug 26 13:25:57 EDT 2016
Fri Aug 26 13:25:58 EDT 2016
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4
  • 2
    Is their a way to save output history from begining when screen is already started without -L ?
    – Nicolas
    Sep 23 '18 at 9:55
  • Thanks for the answer. I tried the screen -dm -L bash -c 'python running_4ever.py' and see the log as well as the newly created screen as detached, I wonder how do we attach to it or kill it? I tried screen -r <screen_id> to it but didn't work.
    – Leo
    Jan 18 '19 at 23:07
  • @Leo this sounds like you need to create a new question
    – Stephen Harris
    Jan 19 '19 at 3:10
  • @StephenHarris Hi Stephen, I figured it out. I tried screen -dm -S <screen_name> -L bash -c "python running_4ever.py" and it worked, then I just used screen -XS <screen_name> quit to kill it. Thanks for the reply though
    – Leo
    Jan 22 '19 at 23:16
7

You should do it the other way round, run script inside screen:

screen -dm bash -c 'script -c "python test.py" output.txt'
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2

Another way to do it is to attach the screen first:

screen -r <pid or name>

and then:

Ctrl+A, H

It will start logging into screenlog.0

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0

Could work!

screen sh -c './some-script 2>&1 | tee mylog.log'
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