gethostbyname

SYNOPSIS

#include <netdb.h>

struct hostent *gethostbyname(const char *name);

Data Structure

http://www.cnblogs.com/LubinLew/p/POSIX-DataStructure.html#struct_hostent 

Description

gethostbyname 是不可重入函数,在多线程编程时需要注意, linux中有可重入版本 gethostbyname_r,

POSIX标准里面使用getaddrinfo和getnameinfo来替换gethostbyname系列函数了，这些函数已经已经被废弃了。 

Parameter

参数 name 既可以是一个主机名(例如"www.163.com"),也可以是IPv4地址(点分十进制形式,例如"111.202.60.48")或者IPv6地址(冒号分隔16进制地址.例如"2000::1:2345:6789:abcd").

如果参数是IPv4或者IPv6地址,那么函数不会执行查询操作,返回的结构体中 h_name 就是该参数的拷贝, h_addr_list[0]就是该参数对应的的整型网络字节(相当于inet_pton(AF_INET*, name, dst)).

 If name doesn’t end in a dot and the environment variable HOSTALIASES is set, the alias file pointed to by HOSTALIASES will first be searched for name (see hostname(7) for the file format).

The current domain and its parents are searched unless name ends in a dot.

Example

#include <stdio.h>
#include <netdb.h>
#include <arpa/inet.h>

int main(void)
{
    int i = 0;
    char str[32] = {0};
     struct hostent* phost = NULL;
 
    phost = gethostbyname("www.163.com");
    if (NULL == phost)
    {
        return -1;    
    }
    
    printf("---Offical name:
	%s
", phost->h_name);

    printf("---Alias name:
");    
    for (i = 0;  phost->h_aliases[i]; i++)
    {
        printf("	%s
", phost->h_aliases[i]);
    }

    printf("---Address list:
");
    for (i = 0; phost->h_addr_list[i]; i++)
    {
        printf("	%s
", inet_ntop(phost->h_addrtype,  phost->h_addr_list[i], str, sizeof(str)-1));
    }

    return 0;
} 

运行结果

---Offical name:
	163.xdwscache.glb0.lxdns.com
---Alias name:
	www.163.com
	www.163.com.lxdns.com
---Address list:
	111.202.60.48
	111.202.60.47