Python tail with grep

Question

Please help me. I have a log files, for example: test_2014_03_13.log

i need tail it with grep and when created new file (test_2014_03_14.log) i need switch tailing with grep to a new file without skipping lines.

i need info about switching without skipping data.

Sorry for my bad english.

Refer to https://stackoverflow.com/questions/1703640/how-to-implement-a-pythonic-equivalent-of-tail-f — Alftheo, Oct 09 '18 at 14:06

ucotta · Answer 1 · 2018-01-29T02:29:59.803

As far as I understand you. I think you want to change the log file when a new one is created.

You need to run two different processes.

The first one to search for changes in the directory so that you know when the new file was created, and then change it.
The second process would be in charge of executing the "Tail+Grep", and when it is closed with the Kill instruction it should continue with the most recent file.

This is an example in Bash that you can easily write in Python. I read too late that you were asking for an example in Python.

#!/bin/bash

pidTail=0

inotifywait -m /var/log/yourfiles -e created |
while read path action file; do 
    echo “changed to $file”
    if [ ! $pidTail -eq 0 ]; then
        kill $pidTail
    fi
    tail -f $file | grep something >> newfile.log & 
    pidTail=$!
done

Note: I've written it right here and I haven't tested it, it may contain typos ;)

Even better late than never!

Sources:

Threads in bash?

Script to monitor folder for new files?

Python tail with grep

1 Answers1