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相关函数原型及参数类型：
函数原型：
int inet_aton(const char *cp, struct in_addr *inp); in_addr_t inet_addr(const char *cp); in_addr_t inet_network(const char *cp); char *inet_ntoa(struct in_addr in); struct in_addr inet_makeaddr(int net, int host); in_addr_t inet_lnaof(struct in_addr in); in_addr_t inet_netof(struct in_addr in);
int inet_pton(int af, const char *src, void *dst);
inet_pton() returns 1 on success (network address was successfully converted). 0 is returned if src does not contain a character string representing a valid network address in the specified
address family. If af does not contain a valid address family, -1 is returned and errno is set to EAFNOSUPPORT.
参数类型：
/* Internet address. */
typedef uint32_t in_addr_t;
struct in_addr
{
in_addr_t s_addr;
};
inet_addr函数：将IPv4的点分十进制地址转换为网络字节序
#include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <arpa/inet.h> int main(int argc, char *argv[])
{
struct in_addr addr;
if (argc != 2) {
fprintf(stderr, "%s <dotted-address>\n", argv[0]);
exit(EXIT_FAILURE);
}
if (inet_aton(argv[1], &addr) == 0) {
perror("inet_aton");
exit(EXIT_FAILURE);
}
printf("addr = 0x%-10x\n", addr.s_addr);
printf("%s\n", inet_ntoa(addr));
exit(EXIT_SUCCESS);
}
yinguicai@Cpl-IBP-Product:~/tmp/network$ ./a.out 127.0.0.1
addr = 0x100007f
127.0.0.1
char *inet_ntoa(struct in_addr in) { static char buf[INET_NTOA_MAX_LEN]; return inet_ntoa_r(in, buf); }
注意：
1、inet_ntoa的返回值是一个static类型的char *指针，所以使用的时候需要注意(不可重入,可以使用线程安全的inet_ntoa_r函数代替)
2、The inet_addr() function converts the Internet host address cp from IPv4 numbers-and-dots notation into binary data in network byte order. If the input is invalid, INADDR_NONE (usually -1) is
returned. Use of this function is problematic(有问题的) because -1 is a valid address (255.255.255.255). Avoid its use in favor of inet_aton(), inet_pton(3), or getaddrinfo(3) which provide a cleaner
way to indicate error return.(因为其返回值为in_addr_t，当返回-1时，有二义性->表示两个含义)
3、inet_aton() returns nonzero if the address is valid, zero if not.
4、inet_aton/inet_addr/inet_ntoa仅适用于ipv4地址
5、inet_pton/inet_ntop对于v4和v6地址均适用
网络地址转换相关函数使用(inet_addr,inet_ntoa,inet_addr)
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原文地址：http://www.cnblogs.com/jingzhishen/p/5605033.html
