Shell script to scans logs for specific signatures

scan_logs.ksh

#!/bin/ksh
#
# Original author: Lance Spitzner, April 1999
#
# Shows last 10 entries of critical system logs.
# Build in some "artificial intelligence" using
# greps and sorts.  You can select a specific
# hosts logs, or you can select all hosts logs.

# Define input
if [ "$1" = "all" ]; then
        system=":"
else
        system=$1
fi

log=$2

# Define logs
inetdlog=/var/adm/inetdlog
messages=/var/adm/messages
syslog=/var/adm/syslog

# Functions
inetdlog () {
echo  "\n\t--- Last 10 entries in $inetdlog ---\n"
grep "$system" "$inetdlog" | grep -v "172.16.1." | tail -10
}

messages () {
echo  "\n\t--- Last 10 entries in $messages ---\n"
grep "$system" "$messages" | egrep -v '(named|MARK)' | tail -10
}

syslog () {
echo  "\n\t--- Last 10 entries in $syslog ---\n"
grep "$system" "$syslog" | tail -10
}

title () {
if [ "$system" = ":" ]; then
        echo  "\n### These are the log results of all systems ###"
else
        echo  "\n### These are the log results of system $system ###"
fi
}

# Actual program
case $log in
        inetdlog)
        title
        inetdlog
        ;;
        messages)
        title
        messages
        ;;
        syslog)
        title
        syslog
        ;;
        all)
        title
        inetdlog
        messages
        syslog
        ;;
        *)
        echo  "\nUsage: `basename $0` <host> <log>"
        echo
        echo "\t<host> "
        echo "\tCan either be a single source you want to grep"
        echo "\tfor in the log, or type \"all\" for all hosts in the" 
        echo "\tlog file."
        echo
        echo "\t<log>"
        echo "\tinetdlog  -> for /var/log/inetdlog"
        echo "\tmessages  -> for /var/log/messages"
        echo "\tsyslog    -> for /var/log/syslog"
        echo "\tall       -> for all three log files\n"
;;
esac

exit 0