grep sed and a loop Post: 302521630

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Top Forums UNIX for Dummies Questions & Answers grep sed and a loop Post 302521630 by agama on Thursday 12th of May 2011 12:21:22 AM

05-12-2011

Registered User

Here is a simple example of how to process a log file and save the last line for reference on the next run. It uses the entire last line from the log as the reference point, rather than a date/time stamp. Less efficient, but more accurate. I'm sure there are other ways to make this more efficient, but this might help get you started.

It does run in Kshell. Should run in bash, but for several reasons I prefer Kshell and didn't test it under bash, so beware if you want to use this as a bash script.

Code:

#!/usr/bin/env ksh


logf=$1                 # log file to suss; supplied as parameter on cmd line
pat=$2                  # pattern to search log for
this=${0##*/}           # base name of script
lastf=/tmp/$this.data   # file where we tuck our last found line away for next time

if [[ -z $logf || -z $pat ]]        # error if logfile name or pattern isn't supplied
then
    echo "usage: $0 log-file-name pattern"
    exit 1
fi

if [[ ! -s $lastf ]]    # no last run data; must check all lines from log
then
    need_all=1          # this will cause us to check for pattern straight away
fi

# parse the log file writing, to stdout, any matches that haven't been seen yet
# The last line seen is written to the last data file for next time.
#
awk  -v snarf=$need_all -v lastf=$lastf -v pat=$pat '
    BEGIN {
        if( !snarf )                # not in check all mode, must find last data
        {
            getline < lastf;
            last_data = $0;
            close( lastf );
        }
    }

    snarf {                         # need all, or found the last line from prev run
        if( match( $0, pat ) )      # if it contains the pattern, print it to stdout
            print;
        new_last = $0;              # save the last line we saw
        next;                       # go to next input line (skip remaining awk code)
    }

    {       # not snarfing yet, check to see if this is the last line we saw before
        snarf = $0 == last_data;    # start snarfing if it matches
        # tricky way of saying:
        # if( $0 == last_data)
        #     snarf = 1;
    }

    END {
        if( new_last )
            printf( "%s\n", new_last) >lastf;   # save our last observed line in the data file.
    }
' <$logf

exit $?           # return the exit code that awk returned with

The one thing this script doesn't do is to deal with the case where the log file has been rolled off. In this case the data file would be non-empty, but we'd need to start checking for the pattern at the start of the log rather than after the previous marker is encountered.

The easy solution to this is to remove the last data file when the log is rolled. If that's not possible, then additional code will be needed to detect this condition; beyond my few minutes to spend answering questions tonight -- sorry.

If you need some info about awk, this is a decent set of doc:
Awk - A Tutorial and Introduction - by Bruce Barnett
and there are other posts on this forum that link other sites.

Hope this helps.

agama

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LEARN ABOUT SUSE

scanlogs

SCANLOGS(8)						    InterNetNews Documentation						       SCANLOGS(8)

NAME

       scanlogs - Summarize and rotate INN log files

SYNOPSIS

       scanlogs [norotate]

DESCRIPTION

       scanlogs summarizes the information recorded in the INN log files which reside in the pathlog directory set in inn.conf (see newslog(5) for
       further details about these log files).	It is normally invoked by the news.daily(8) script which performs daily server maintenance tasks.

       It invokes "ctlinnd flushlogs" to close the news and error log files, rename them to add ".old" to the file names and open fresh news and
       error logs; the active file is also flushed to disk, along with the history database.

       By default, scanlogs rotates and cleans out the logs.  It keeps up to logcycles old compressed log files in pathlog/OLD (the logcycles
       parameter can be set in inn.conf).   scanlogs also keeps archives of the active file in this directory.

       It invokes tally.control if newgroup.log or rmgroup.log exists in pathlog (see the control.log entry of newslog(5) for more information
       about that).

       scanlogs displays the contents of errlog and news.crit, if non-empty, and runs innreport to summarize the contents of news and news.notice,
       and to update the unwanted.log file amongst other things (see more information about that in innreport(8)).

OPTIONS

       Only one option is currently accepted:

       norotate
	   Using this option disables the rotating and cleaning aspect of the log processing:  the logs files are only scanned for information and
	   no contents are altered.  If scanlogs is invoked more than once a day, the norotate option should be used to prevent premature log
	   cleaning.

FILES

       See newslog(5) for the list of log files processed by scanlogs.

HISTORY

       Written by Landon Curt Noll <chongo@toad.com> and Rich $alz <rsalz@uunet.uu.net> for InterNetNews.  Converted to POD by Julien Elie.

       $Id: scanlogs.pod 8357 2009-02-27 17:56:00Z iulius $

SEE ALSO

       inn.conf(5), innreport(8), news.daily(8), newslog(5), shlock(1), tally.control(8).

INN 2.5.2							    2009-05-21							       SCANLOGS(8)

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