Python on system start up

Question

I am running Python on a Raspberry Pi and everything works great. I have a small script running on the system start up which prints several warning messages (which I actually cannot read since it is running in the background)...

My question is: Is there a way via SSH to "open" this running script instance and see what is going on or a log file is the only way to work with that?

Thanks!

you can write the warning message to file then read it later — Hackaholic, Dec 15 '14 at 19:00
it is not clear what you are asking, what exactly are you trying to read? — Padraic Cunningham, Dec 15 '14 at 19:01
a script does not change so I cannot see how looking inside it will do much — Padraic Cunningham, Dec 15 '14 at 19:04
The messages depend on sensors installed to the Raspberry Pi. So the script does not change but the messages do. :) — , Dec 15 '14 at 19:05
then you want the output from running the script not to access the script. Have you tried outputting the data as the script runs? — Padraic Cunningham, Dec 15 '14 at 19:06
possible duplicate of [Attach to a processes output for viewing](http://stackoverflow.com/questions/715751/attach-to-a-processes-output-for-viewing) — holdenweb, Dec 15 '14 at 19:58

Tim Tisdall · Accepted Answer · 2014-12-16T16:50:00.980

Try using the Python logging library. You can configure it to save the output to a file and then you can use tail -f mylogfile.log to watch as content is put in.

EDIT:

An alternative is to use screen. It allows you to run a command in a virtual console, detach from that console, and then disconnect from the machine. You can then reconnect to the machine and re-attach to that console and see all the output the process made. I'm not sure about using it on a script that starts when the machine is turned on, though (I simply haven't tried it).

score 0 · Answer 2 · answered Dec 15 '14 at 22:54

You should modify your python script to write its output to a file instead of to the screen (which you can't see). I.e., I think that a log file is your best (possibly only) bet. You can write to a file in /tmp on the raspberry pi if you just want a temporary log file that you can check once and a while. Also, as Tim said, you could try out the python logging library, but I think just writing to a file is quicker and easier, although you might run into some issues with permissions...

Python on system start up

2 Answers2