判断字符串是否是正确的IP格式的C语言函数

来自：http://blog.csdn.net/shanzhizi

一个用于识别字符串是否是IPV4的C语言函数，保留下来供大家参考使用：

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

int if_a_string_is_a_valid_ipv4_address(const char *str)
{
    struct in_addr addr;
    int ret;
    volatile int local_errno;

    errno = 0;
    ret = inet_pton(AF_INET, str, &addr);
    local_errno = errno;
    if (ret > 0)
        fprintf(stderr, "\"%s\" is a valid IPv4 address\n", str);
    else if (ret < 0)
        fprintf(stderr, "EAFNOSUPPORT: %s\n", strerror(local_errno));
    else 
        fprintf(stderr, "\"%s\" is not a valid IPv4 address\n", str);

    return ret;
}

int main()
{
	char *pIP = "192.168.0.22";
	char *pNotIP ="192.168.0.256";
	
	if_a_string_is_a_valid_ipv4_address(pIP);
	if_a_string_is_a_valid_ipv4_address(pNotIP);
	
	return 0;
}