用ping檢測網段ip的佔用情況

寫法一：
#!/bin/sh
addr="192.168.10"
for ip in $( seq 1 100 )
do
ping -c 1 -w 1 ${addr}.${ip} &> /dev/null && num=1 ||num=0
if [ "$num" -eq 0 ] ; then
     echo "${addr}.${ip} is down"
fi
done

寫法二：
for i in $(seq 1 254) ; do ping -w 1 -c 1 192.168.10.${i} &>/dev/null  || echo "192.168.10.${i} is up" ; done