Posts tagged How to validate an IP address in string format

The library function inet_aton can be used to extract IP address from a string format (eg: “123.23.42.76″). This function returns non-zero value if the IP address is valid and zero if it is an invalid IP address. The following example shows how to use this library function.

#include <stdio.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

char *ips[] = {
   "12.34.56.7",
   "123.123.123.123",
   "255.255.255.255",
   "345.123.23.54",
   NULL
};

int main(int argc, char *argv[])
{
   int i;
   struct in_addr ia;

   i = 0;
   while(ips[i]) {
   if(inet_aton(ips[i],&ia) == 0) {
     printf("%s is an INVALID ip address\n", ips[i]);
   } else {
     printf("%s is a VALID ip address. 0x%lx\n", More >