Ping IPs by subnet and show simple up/down status

sping.sh

#!/bin/bash

# [user@server ~]$ sping.sh 70.120.121.0/29
# 70.120.121.1 down
# 70.120.121.2 up
# 70.120.121.3 up
# 70.120.121.4 up
# 70.120.121.5 up
# 70.120.121.6 up

# configuration variables

# absolute path to directory containing sping.sh, without trailing /
DIR="/usr/local/bin"

# maximum number of concurrent pings
MAX_WORKERS=50

# support programs

declare -A hosts

hosts[30]=1
hosts[29]=5
hosts[28]=13
hosts[27]=29
hosts[26]=61
hosts[25]=125
hosts[24]=253
hosts[23]=509
hosts[22]=1021
hosts[21]=2045
hosts[20]=4093
hosts[19]=8189
hosts[18]=16381
hosts[17]=32765
hosts[16]=65533
hosts[15]=131069
hosts[14]=262141
hosts[13]=524285
hosts[12]=1048573
hosts[11]=2097149
hosts[10]=4194301
hosts[9]=8388605
hosts[8]=16777213

function show_help()
{
    echo "usage: sping.sh 192.168.0.0/24"
}

function ip2int()
{
    int=0

    for octet in ${1//./ }
    do
        int=$((256*$int+$octet))
    done

    echo $int
}

function int2ip()
{
    echo "$(($1 / 16777216)).$(($(($1 % 16777216)) / 65536)).$(($(($1 % 65536)) / 256)).$(($1 % 256))"
}

function ping_host()
{
    ping -c3 -i.2 -W1 -q "$1" 2> /dev/null | grep rtt &> /dev/null

    if [ $? -eq 0 ]
    then
        echo "$1 up"
    else
        echo "$1 down"
    fi
}

function build_list()
{
    list=""
    start=$(($(ip2int $1)+1))
    stop=$(($start+${hosts[$2]}))

    for ip in $(seq "$start" "$stop")
    do
        list+="$(int2ip $ip)\n"
    done

    echo "$list"
}

# main program

if [ "$1" = "worker" ]
then
    result=$(ping_host $2)
    echo "$result"
else
    IFS='/'

    read -a INPUT <<< "$1"

    unset IFS

    if [ "${#INPUT[@]}" -ne 2 ]
    then
        show_help
        exit 1
    elif [ "${INPUT[1]}" = "-h" -o "${INPUT[1]}" = "--help" ]
    then
        show_help
        exit 0
    elif [ "${INPUT[1]}" -lt 8 -o "${INPUT[1]}" -gt 30 ]
    then
        echo "invalid subnet mask"
        exit 1
    fi

    list=$(build_list ${INPUT[0]} ${INPUT[1]})

    echo -e "$list" | xargs -n 1 -I ^ -P "$MAX_WORKERS" $DIR/sping.sh worker ^ | sort -t . -k 3,3n -k 4,4n
fi