Shell Programming and Scripting

subnet () 
{  
   clear         
   while true         
   do                 
      echo "\n "                 
      echo "Please enter the subnet to be changed: \c"                 
      read sub                 
      grep -w "$sub" subnet                 
      if [[ $? -eq 0 ]]                 
      then                         
           print "Matched"                         
           break;                 
      else 
           echo "\n\n\tNot a valid subnet - please try again.";                 
      fi         
   done 
}

grep -i "$ip" file

# cat subnet
111.222.333.0
222.111.333.0
333.222.111.0

# grep -w "111" subnet
111.222.333.0
222.111.333.0
333.222.111.0
# grep -w "^111" subnet
111.222.333.0