:
##########################################################################
# Title      :	collectethers - create database of ethernet addresses
# Author     :	Heiner Steven <heiner.steven@odn.de>
# Date       :	1998-11-25
# Requires   :	arp
# Category   :	System Administration
# SCCS-Id.   :	@(#) collectethers	1.4 04/02/18
##########################################################################
# Description
#
##########################################################################

PN=`basename "$0"`			# Program name
VER='1.4'

# Search PATH for a new AWK (or GNU AWK)
for path in `echo "$PATH" | sed 's/^:/.:/;s/:$/:./;s/:/ /g'`
do
    [ -x "$path/gawk" ] && : ${NAWK=$path/gawk}
    [ -x "$path/nawk" ] && : ${NAWK=$path/nawk}
done
: ${NAWK=awk}

ARP="arp -a"

PrettyPrint=no
Interval=60
HostPattern=
Ethers=ethers.list

Usage () {
    echo >&2 "$PN - collect ethernet addresses, $VER
usage: $PN [-i interval] [-m hostmatch] [filename]
   or: $PN -p [filename ...]
    -i: update interval (default is $Interval, 0 means \"run once\")
    -m: string to match hostname part of \"$ARP\" output (default: domainname)

The first usage periodically calls the command "$ARP", and collects
ethernet addresses in a file (the default is \"$Ethers\").

The second usage pretty prints ethernet addresses."
    exit 1
}

Msg () {
    for MsgLine
    do echo "$PN: $MsgLine" >&2
    done
}

Fatal () { Msg "$@"; exit 1; }

Tmp=${TMPDIR:=/tmp}/$PN.$$

set -- `getopt hi:p "$@"`
[ $# -lt 1 ] && Usage			# "getopt" detected an error

while [ $# -gt 0 ]
do
    case "$1" in
    	-m)	HostPattern="$2"; shift;;
	-i)	Interval="$2"; shift;;
	-p)	PrettyPrint=yes;;
	--)	shift; break;;
	-h)	Usage;;
	-*)	Usage;;
	*)	break;;			# First file name
    esac
    shift
done

if [ $PrettyPrint = yes ]
then
    # Input example:
    : '
    00:60:08:22:e9:d9 host.dev.null.de
    8:0:20:95:eb:78 lorenz
    '
    exec $NAWK '
	{
	    for ( i=1; i<=NF; ++i ) {
	    	if ( $i ~ /^[0-9a-fA-F][0-9a-fA-F]*:/ ) {
		    addr = $i
		    k = split (addr, a, ":")
		    newaddr = ""
		    for ( j=1; j<=k; ++j ) {
			if ( newaddr != "" ) newaddr = newaddr ":"
			part = a [j]
			if ( length (part) == 1 ) {
			    newaddr = newaddr "0" part
			} else {
			    newaddr = newaddr part
			}
		    }
		    $i = newaddr
		}
	    }
	    print
	}
    ' "$@"
    # NOT REACHED
fi

[ $# -lt 1 ] && set -- "$Ethers"
[ $# -ne 1 ] && Fatal "please specify excactly one file name"

Ethers="$1"

# Ethers database must already exist
[ -f "$Ethers" ] || > "$Ethers" || exit 1

: ${HostPattern:=224.0.0.0}
: ${HostPattern:=`domainname`}
[ -z "$HostPattern" ] && Fatal "please specify host string"

# Determine the columns in the "arp" output for hostname
# and ethernet address
eval `$ARP |
    $NAWK '
    BEGIN { namecol=0; addrcol=0; }
    {
        for ( i=1; i<=NF; ++i ) {
	    field = $i
	    if ( !namecol && field ~ /'"$HostPattern"'/ ) namecol = i
	    if ( !addrcol && field ~ /^[0-9a-fA-F][0-9a-fA-F]*:/ ) addrcol = i
	    if ( namecol && addrcol ) exit (0)
	}
    }
    END {
        print "namecol=" namecol
	print "addrcol=" addrcol
    }
    '`

: ${namecol:=2}
: ${addrcol:=4}

trap 'rm -f "$Tmp" >/dev/null 2>&1' 0
trap "exit 2" 1 2 3 13 15

while :
do
    $ARP |
    	$NAWK '
	    BEGIN {
	    	Ethers = "'"$Ethers"'"
		while ( getline < Ethers ) {
		    nameof [$1] = $2
		}
		close (Ethers)
	    }

	    $addrcol ~ /^[0-9a-fA-F][0-9a-fA-F]*:/ {
	    	addr = $addrcol
		name = $namecol
		if ( nameof [addr] != "" ) {
		    if ( nameof [addr] != name ) {
		    	print "WARNING: IP address for mac address " addr \
				" changed from " name " to " nameof [addr] \
				| "cat >&2"
		    }
		}
		nameof [addr] = name
	    }
	    END {
	    	for ( addr in nameof ) {
		    print addr, nameof [addr]
		}
	    }
	' namecol=$namecol addrcol=$addrcol > "$Tmp" && mv "$Tmp" "$Ethers" ||
		exit

    [ "$Interval" = "0" ] && exit 0
    sleep $Interval || exit
done