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Full Discussion: Would appreciate a quick second set of eyes on a script (regarding doing things in the background)
Top Forums Shell Programming and Scripting Would appreciate a quick second set of eyes on a script (regarding doing things in the background) Post 302435451 by DeCoTwc on Wednesday 7th of July 2010 11:32:05 AM
Old 07-07-2010
Would appreciate a quick second set of eyes on a script (regarding doing things in the background)
What I'm trying to do is leave a tcpdump running all the time on a server, and at the end of every day kill it and start a new one. For some reason my boss doesn't want to set this up as a cron job, so I've come up with the following.:

Code:
#!/bin/bash

PCAPFILE=/tmp/mgmt.$(date "+%H.%M.%S.%m.%d").pcap

tcpdump -i eth0 -nn -vv -s 1500 net 192.168.5 -w $PCAPFILE   2>&1 & 
dumpPid=$!


TDATE=$(date --date='-1 days ago' "+%m.%d.%y")
DATE=$(date "+%m.%d.%y")


killDump ()
{
    kill $dumpPid
}


zipPcap ()
{
    gzip -c $1 > $1.gz && rm $1
}


    while true; do
        until [[ "$DATE" == "$TDATE" ]]; do
            sleep 1800
        done
        killDump
        zipPcap $PCAPFILE &
        PCAPFILE=/tmp/mgmt.$(date "+%H.%M.%S.%m.%d").pcap
        tcpdump -i eth0 -nn -vv -s 1500 net 192.168.5 -w $PCAPFILE   2>&1 & 
        dumpPid=$!
        TDATE=$(date --date='-1 days ago' "+%m.%d.%y")
        DATE=$(date "+%m.%d.%y")
    done

I've tested this on a small scale on my personal laptop, but I've made a minor change as highlighted above that I want to make sure shouldn't cause any problems.

Since by the end of the day the pcap is probably going to be rather large, I don't want the script to have to wait for the old one to finish zipping before it starts the next capture, so is running the zipPcap function in the background like that an acceptable way of kicking off the compression, and having the rest of the script move forwards?

I'm pretty confident this should be fine, but as I'm working without a lab to test on right now, I wanted to get a second set of eyes.
 

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LEARN ABOUT DEBIAN

netsds::util::datetime

NetSDS::Util::DateTime(3pm)				User Contributed Perl Documentation			       NetSDS::Util::DateTime(3pm)

NAME

       NetSDS::Util::DateTime - common date/time processing routines

SYNOPSIS

	       use NetSDS::Util::DateTime;

	       print "Current date: " . date_now();

DESCRIPTION

       This package provides set of routines for date and time processing.

EXPORTED FUNCTIONS

       date_now_array([TIME])
	   Returns array of date items for given date.	If source date is not set current date used.

       date_now([TIME])
	   Return [given] date as string.

	       2001-12-23 14:39:53

       date_now_iso8601([TIME])
	   Return date as ISO 8601 string.

	       20011223T14:39:53Z

	   <http://en.wikipedia.org/wiki/ISO_8601> http://www.w3.org/TR/NOTE-datetime <http://www.w3.org/TR/NOTE-datetime>

       date_strip(DATE)
	   Trim miliseconds from date.

       date_date(DATE)
	   Trim time part from date.

       date_time(DATE)
	   Trim date part from date.

       time_from_string($string)
	   Return parsed date/time structure.

       date_from_string($string)
	   Return date from string representation.

       date_inc([INCREMENT, [TIME]])
	   Return date incremented with given number of seconds.

       date_inc_string([INCREMENT, [TIME]])
	   Return string representation of date incremented with given number of seconds.

EXAMPLES

       None yet

BUGS

       Unknown yet

SEE ALSO

       Date::Parse, Date::Format

TODO

       Import stuff from Wono project

AUTHOR

       Valentyn Solomko <val@pere.org.ua>

       Michael Bochkaryov <misha@rattler.kiev.ua>

perl v5.12.4							    2011-08-27					       NetSDS::Util::DateTime(3pm)
All times are GMT -4. The time now is 10:26 AM.
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