hostlist - lists all live hosts in local network

#!/bin/bash
#
# hostlist - Scans LAN and lists hostnames from live hosts, saving to file
#
#    Copyright (C) 2011 Rodrigo Silva (MestreLion) <[email protected]>
#
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation, either version 3 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License
#    along with this program.  If not, see <http://www.gnu.org/licenses/gpl.html>.
#
# Quick-and-dirty script to feed bash completion for known hosts, using the
# currently-unused-and-soon-to-be-deprecated ~/ssh/known_hosts2 file. It uses
# smbtree, avahi-browse and ping to generate the list of live hosts

exec 3> /dev/null
self="${0##*/}"

# default settings
config="${HOME}/ssh/known_hosts2"

usage()
{
cat <<- USAGE
    Usage: $self [--verbose] [--purge] [--config FILE]
USAGE
if [[ "$1" ]] ; then
    cat <<- USAGE
        Try '$self --help' for more information.
    USAGE
    exit 1
fi
cat <<-USAGE
    Generates a list of live hostnames on LAN, adding new results to a file

    Options:
    -v|--verbose     - print more details about what is being done
    -p|--purge       - deletes all entries and re-creates the list with current scan results
    -c|--config FILE - use FILE for storing results instead of the default file
                       NOTE: -cFILE or --config=FILE syntax is NOT supported

    If used without any options, default behavior is to add new hostnames to
    $config . Only the first "hosts" entry (if any) is read and changed.
    All other settings in the file are ignored.
USAGE
exit 0
}
invalid()
{
    echo "$self: unrecognized option '$1'"
    usage 1
}

while [[ $# -gt 0 ]]; do
    arg="$1"; shift
    case "$arg" in
    -h|--help   ) usage               ;;
    -v|--verbose) verbose=1           ;;
    -p|--purge  ) purge=1             ;;
    -c|--config ) config="$1" ; shift ;;
    *           ) invalid "$arg"      ;;
    esac
done

myip=$(ifconfig eth0 | grep 'inet addr:' | cut -d: -f2 | cut -d' ' -f1)
subnet=${myip%.*}

hosts=$(
    {
        for ip in {1..254} ; do
            { ping -n -c 1 -W 1 "${subnet}.${ip}" >&3 && { getent hosts "${subnet}.${ip}" | awk '{print $2}' ; } ; } &
        done
        smbtree -NS | awk -F '\t' '$2{ gsub(/^\\\\| +/,"",$2); print tolower($2) }'
        avahi-browse --terminate --parsable --no-db-lookup --resolve _workstation._tcp | awk -F ';' '$1=="="{ print $(NF-3) }'
    } | sort -u | awk '$0 != prev".local" { print ; prev=$0 }'
)

echo "$hosts"

# References
#avahi-browse --terminate --parsable --no-db-lookup _workstation._tcp | awk -F ';' '$3=="IPv4"{ gsub(/\\.*/,"",$4) ; print $4"."$(NF) }'
#perl -ne 'print "$1 " if /^Host (.+)$/' ~/.ssh/config ; complete -W "$(_ssh_completion)" ssh
#complete -W "$(echo `cat ~/.ssh/known_hosts | cut -f 1 -d ' ' | sed -e s/,.*//g | uniq | grep -v "\["`;)" ssh
#complete -W "$(echo $(grep '^ssh ' .bash_history | sort -u | sed 's/^ssh //'))" ssh
#reverse netbios: nmblookup
#reverse avahi: avahi-resolve -a ipaddress

#desktop
#helena
#vb-debian604.local
#vb-fedora16.local
#vb-lfs-build
#vb-xp
#vb-win7