用C以点分十进制形式获取我机器的IP地址？

Question

I'm trying to get a string with the ip address in dotted decimal of my machine. What I do is trying to get the string from INADDR_LOOPBACK with the following code.

char addr[INET_ADDRSTRLEN];
struct in_addr *in_addr1 = malloc(sizeof(struct in_addr));
in_addr1->s_addr = INADDR_LOOPBACK;
inet_ntop(AF_INET, in_addr1, addr, INET_ADDRSTRLEN);
printf("addr: %s\n", addr);

Here's what I get from the printf :

1.0.0.127

1. Why is it the localhost address reverse? Should it print 127.0.0.1 ?
2. Honestly I was expecting to get the ip I would get calling for example $ ifconfig ... not the localhost! Did I misunderstand what INADDR_LOOBACK does?

Answer 1

INADDR_LOOPBACK is in host byte order , ie 0x7f000001 . It is, incidentally, the IPv4 address 127.0.0.1 .

in_addr1->s_addr must be in network byte order .

Your computer is a little-endian computer where the host byte order doesn't match the network byte order. You must use htonl to convert the loopback address to network byte order.