Save and restore settings on /from SD card

Using Arduino Programming Questions
1

Hello all!
The main idea is to have web interface to configure LAN settings.
i have to write LNA settings to SD card in text file(mac,ip) it's work ok.
i need to read these settings and put it in Ethernet.begin(mac, ip);
i read from text file ip address {192,168,100,155} but it text. in function Ethernet.begin(mac, ip); it use byte variables. the problem is how to convert string {192,168,100,155} to byte value that will work function Ethernet.begin(mac, ip);

can you help me? thank you in advance.

2

the problem is how to convert string {192,168,100,155} to byte value that will work function Ethernet.begin(mac, ip);

If you really have a string (not a String), strtok() and atoi() will be useful functions. If you have a String, don't.

3

it finally i have like in this sample
String str="";
byte ip;
str="{192,168,100,155}";

now i need to convert str to ip.
how it can be done?

4

how it can be done?

The String class is fairly well documented. Look at the documentation your self.

Or, get smarter:

byte ipAdd[4];
char *ipStr = "192,168,100,155";
char *pToken = strtok(ipStr, ",");
if(pToken)
{
   ipAdd[0] = atoi(pToken);
   pToken = strtok(NULL, ","); // Keep parsing same string
   if(pToken)
   {
      ipAdd[1] = atoi(pToken);
      pToken = strtok(NULL, ","); // Keep parsing same string
      if(pToken)
      {
         ipAdd[2] = atoi(pToken);
         pToken = strtok(NULL, ","); // Keep parsing same string
         if(pToken)
         {
            ipAdd[3] = atoi(pToken);
         }
      }
   }
}
5

thank you!