Re: Inner exit status code

[joshebosh]

maybe try this?

when thinking outside the screen program

1. start up screen with an expectation there's more to do when screen quits, like check a file with a result

screen && cat /tmp/exit_code    # if your intent is exit screen normally, the use AND "&&"... otherise if your screen session is killed abnormally from some other terminal, you might need to use  OR "||"

2. while inside screen, expect that the final line of your script will ALWAYS be storage mechanism for the previous command

cat /tmp/nosuchfile     # last desired command in script (i'm intentionally getting an exit code code here other than zero)

echo $? > /tmp/exit_code        # storing exit status of that last command, which is the final command in script

screen -X quit              # exit screen either manually, or via script

3. Once screen exits you should see the exit status of that last desired command from script

-------------------

[screen is terminating]

1 

--------------------

does that help you?

On Wed, May 8, 2024 at 2:41 PM Alan D. Salewski <salewski@att.net> wrote:

On 2024-05-07 10:24:49, Marek Lukács <marek@lukacs.cz> spake thus:
>Is it possible to capture last exit status code after screen finished (eg.
>environment variable $SCREEN_EXIT_CODE), or copy last status code to screen'
>s exit status code, so I can check it using $? ?

Hi Marek,

I'm not aware of any way to cause a program's exit status to be
reflected in the exit status of 'screen' itself. But even if that
were possible, it would probably be less reliable than you would
want, because the ability to detect an error by the status code
would then depend on the order in which subprocesses exit within
screen.

E.g., if a given screen session runs two subprocesses, and the first
one exits with a non-zero (error) status and the other exits with a
zero (success) status a moment later, then having the "last exit
status code" reflected in the exit status of the screen process
would still mask the error of the subprocess that failed.

A different approach would be to use wrapper scripts that write
their exit statuses to some well-known location in the file
system. Rather than have screen launch your program(s) directly, it
would instead launch a corresponding wrapper script:

     #!/bin/sh
     /path/to/some/program "$@"
     printf '%s\n' "$?" >> /path/to/estat

To make that approach as reliable as possible, it would be best to
create '/path/to/estat' prior to launching the subprocess in the
screen session. That would allow you to detect "file system full" or
situations in which there are inadequate persmissions to write the
exit status file.

Best regards,
-Al

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