script: massping.sh: mass ping scanner

pretty fast
i know.. some ranges are not valid. More checking needs to be done

#!/bin/bash
#
# ./shping.sh 192.168.0.1-150

function usage() {
   echo "usage example: $0 192.168.0.1-100"
   exit 1
}

IFS='.'
iprange=($@)               # 192 168 0 1-100
IFS=$'\040\t\n'            # printf "$IFS"|hexdump -bc
srange=${iprange[3]/%-*/}  # 1
erange=${iprange[3]/#*-/}  # 100
j=0

# Do some checking
[ "$#" == "1" ]                              && # only 1 arg
   [ ${iprange[*]//[[:digit:]]/} ]           && # does it exist?
      [ ${#iprange[@]} == 4 ]                && # x.x.x.x
         [ ${iprange[*]//[[:digit:]]/} == "-" ]    ||
            usage


# values within 0.0.0.0-255.255.255.255
for i in "${iprange[@]:0:3}" "$srange" "$erange"; do
   [ $i ]               &&
      [ $i -le 255 ]    &&
         [ $i -ge 0 ]   ||
            usage
done

# change 192.168.0.10-1 to 192.168.0.1-10
if [ $srange -gt $erange ]; then
   trange=$srange
   srange=$erange
   erange=$trange
fi

# add dots & feed the array
for ((i=$srange; $erange >= i; i++)) do
   iplist[$j]="${iprange[@]:0:3}.$i"
   iplist=("${iplist[@]// /.}")
   (( j++ ))
done

# now feed ping with random ips
for i in ${iplist[@]}; do
   r=$(( RANDOM%${#iplist[@]} ))
   ping -c1 -s0 ${iplist[$r]}>/dev/null && echo ${iplist[$r]} &
   iplist[$r]=""
   iplist=(${iplist[@]})
done

exit 0;