0

I have this screen process which has open my serial port:

$ sudo lsof | grep /dev/ttyS0
    screen    23520        root    6u      CHR               4,64         0t0       1421 /dev/ttyS0
$ cd /proc/23520
$ head -n 5 status
    Name:   screen
    State:  S (sleeping)
    Tgid:   23520
    Pid:    23520
$ screen -ls
    There is a screen on:
        21200.pts-1.porkypig    (07/10/2013 12:25:42 PM)    (Detached)
$ screen -r 21200.pts-1.porkypig

When I reattached to the screen session, to see exactly what it's doing. I see this long log of information. It seems like the result of "tail -f", that is, a continous log being output.

/proc/23520 $ cd cwd
 pwd
/proc/23520/cwd
ls -l
-rw-r--r--  1 root        root        2147 2013-10-07 17:55 minicom.log

When I switch into the directory (cwd) that this process was run from, I notice minicom.log, which makes me suspect the user ran something like "tail -f minicom.log".

I know that in linux we can use history to track back commands that were run. But how can I confirm the command was run to display what I am currently looking at in my screen session?

2 Answers 2

0

The best way would be to strace the PID.

For example; screen sessions are located in /var/run/screen/<screen session>. If you ls in that directory you'll see the PID of the session.

You can then strace -p <pid> on that PID. It wont be pretty but it's the closest you'll get.

1
  • When I do that, I just get this: strace -p 23520 Process 23520 attached - interrupt to quit select(1024, [3 6], [], NULL, NULL Oct 9, 2013 at 20:20
0

In your case the screen PID is 21200 (according to the screen -ls command). So pstree 21200 will do. Similarly, htop in tree mode (press [F5]) will also see the process tree.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.