Snort alert tail...

holger krekel pyth at devel.trillke.net
Sun Jun 16 20:04:39 CEST 2002


Cliff Wells wrote:
> On Sun, 2002-06-16 at 05:51, Jan-Eric wrote:
> > HEllo !
> > I'm trying to write a dynamic firewall script in python that scans the Snort 
> > alert file like 'tail -f' and takes action based on the infomation it gets 
> > from that file. But I can't get the 'tail' function to work.It reads the 
> > file, but any new information that Snort is writing to the file doesn't 
> > show up to the script.
> > 
> > ex.
> > file = open('/var/log/snort', 'r')
> > while 1:
> >         file = file.read()
> >         print file
> > ....
> 
> 
> import os, stat
> import time
> 
> def snort(pathname):
>     size = os.stat(pathname)[stat.ST_SIZE]
>     
>     while 1:
>         lastsize = size
>         size = os.stat(pathname)[stat.ST_SIZE]
>         if size > lastsize: # there's new data
>             f = open(pathname, 'r')
>             f.seek(lastsize)
>             print f.readlines()
>             f.close()
>         else:
>             time.sleep(2)

i'd recommend checking for 'size<lastsize' also and setting lastsize=0
in this case. Otherwise a rewritten/truncated file gets you bad
behaviour.

regards,

    holger





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