ifconfig | awk '/inet/{print $2}' | awk -F: '{print $2}' 

CheckIPAddress()        {         echo $1 > /tmp/tmpserverip         echo $1 |grep "^[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}$" > /dev/null         if [ $? = 1 ];    then                 return 1         else                 a=$(cut -d. -f1 /tmp/tmpserverip)                 b=$(cut -d. -f2 /tmp/tmpserverip)                 c=$(cut -d. -f3 /tmp/tmpserverip)                 d=$(cut -d. -f4 /tmp/tmpserverip)                     for loop in $a $b $c $d                 do                         if [ $loop -ge 255 ] || [ $loop -le 0 ]; then                                 return 2                         fi                 done         fi                     return 0 }

grep "^([01]?\d\d?|2[0-4]\d|25[0-5])\.([01]?\d\d?|2[0-4]\d|25[0-5])\.([01]?\d\d?|2[0-4]\d|25[0-5])\.([01]?\d\d?|2[0-4]\d|25[0-5])\.$"

echo -n 'Enter the Server-ip:'         read BISSip         echo $BISSip > /tmp/tmpserverip         echo $BISSip|grep "^[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}$" > /dev/null         num=$?         if [ $num = 1 ]         then                 echo error ip,please enter correct                else   {         a=$(cut -d. -f1 /tmp/tmpserverip)         b=$(cut -d. -f2 /tmp/tmpserverip)         c=$(cut -d. -f3 /tmp/tmpserverip)         d=$(cut -d. -f4 /tmp/tmpserverip)            {                 if [ $a -ge 255 ]||[ $a -le 0 ]                 then                         echo a:error ip                 else                         echo 1 > /tmp/jack                  fi         }            {                 if [ $b -ge 255 ]||[ $b -lt 0 ]                 then                         echo b:error ip         else                         echo 1 >>/tmp/jack         fi            }             { if [ $c -ge 255 ]||[ $c -lt 0 ]                  then                          echo c:error ip                 else                         echo 1 >>/tmp/jack                     fi          }             { if [ $d -ge 255 ]||[ $d -le 0 ]                 then                         echo d:error ip                 else                         echo 1 >> /tmp/jack                 fi          }