GETHOSTBYNAME

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#include <netdb.h>
extern int h_errno;

struct hostent *gethostbyname(const char *name);

#include <sys/socket.h>        /* for AF_INET */
struct hostent *gethostbyaddr(const char *addr,
  int len, int type);

void sethostent(int stayopen);

void endhostent(void);

void herror(const char *s);

const char * hstrerror(int err);

ÀâÌÀ

gethostbyaddr() ´Ø¿ô¤ÏÍ¿¤¨¤é¤ì¤¿¥Û¥¹¥È¥¢¥É¥ì¥¹ addr (Ťµ len¡¢ ¥¿¥¤¥× type) ¤ËÂбþ¤¹¤ë¹½Â¤ÂÎ hostent ¤òÊÖ¤¹¡£¸½ºßÍѤ¤¤ë¤³¤È¤Î¤Ç¤­¤ë¥¿¥¤¥×¤Ï AF_INET ¤Î¤ß¤Ç¤¢¤ë¡£

sethostent() ´Ø¿ô¤Ï¡¢¥Í¡¼¥à¥µ¡¼¥Ð¡¼¤Ø¤ÎÀܳÍͼ°¤ò»ØÄꤹ¤ë¡£ stayopen ¤¬¿¿ (1) ¤Ê¤é¤Ð¡¢¥Í¡¼¥à¥µ¡¼¥Ð¡¼¤Ø¤ÎÌ䤤¹ç¤ï¤»¤Ë¤Ï¡¢Àܳ¤µ¤ì¤¿ TCP ¥½¥±¥Ã ¥È¤òÍѤ¤¡¢Ï¢Â³¤·¤¿Ì䤤¹ç¤ï¤»¤Î´Ö¤ËÀܳ¤ò°Ý»ý¤¹¤ë¡£µ¶¤Ê¤é¤Ð¥Í¡¼¥à¥µ¡¼¥Ð¡¼ ¤Ø¤ÎÌ䤤¹ç¤ï¤»¤Ë UDP ¥Ç¡¼¥¿¥°¥é¥à¤òÍѤ¤¤ë¡£

endhostent() ´Ø¿ô¤Ï¥Í¡¼¥à¥µ¡¼¥Ð¡¼¤Ø¤ÎÌ䤤¹ç¤ï¤»¤ËÍѤ¤¤¿ TCP Àܳ¤ÎÍøÍѤò½ªÎ»¤¹¤ë¡£

herror() ´Ø¿ô (¤â¤¦¸Å¤¤) ¤Ï¸½ºß¤Î h_errno ¤ËÂбþ¤¹¤ë¥¨¥é¡¼¥á¥Ã¥»¡¼¥¸¤ò stderr ¤Ë½ÐÎϤ¹¤ë¡£

hsterror() ´Ø¿ô (¤â¤¦¸Å¤¤) ¤Ï¥¨¥é¡¼ÈÖ¹æ (ŵ·¿Åª¤Ë¤Ï h_errno) ¤ò °ú¿ô¤Ë¼è¤ê¡¢Âбþ¤¹¤ë¥¨¥é¡¼¥á¥Ã¥»¡¼¥¸Ê¸»úÎó¤òÊÖ¤¹¡£

gethostbyname() ¤È gethostbyaddr() ¤Ë¤è¤Ã¤Æ¼Â¹Ô¤µ¤ì¤ë¥É¥á¥¤¥ó̾¤ÎÌ䤤¹ç¤ï¤»¤Ç¤Ï¡¢¥Í¡¼¥à¥µ¡¼¥Ð¡¼ named(8)¡¢ /etc/hosts ¤Î¥Ç¡¼¥¿¹Ô¡¢¤ª¤è¤Ó Network Information Service (NIS ¤Þ¤¿¤Ï YP) ¤Î¤¤¤º¤ì¤«¡¢¤¢¤ë¤¤¤Ï¤¹¤Ù¤Æ¤¬ÍѤ¤¤é¤ì¤ë¡£¤³¤ì¤Ï /etc/host.conf ¤Î order ¹Ô¤ÎÆâÍƤ˰͸¤¹¤ë (¾Ü¤·¤¯¤Ï resolv+(8) ¤ò¸«¤è)¡£ ¥Ç¥Õ¥©¥ë¥È¤Ç¤Ï¤Þ¤º named (8) ¤ËÌ䤤¹ç¤ï¤»¡¢¼¡¤¤¤Ç /etc/hosts ¤ò±ÜÍ÷¤¹¤ë¡£

hostent ¹½Â¤ÂÎ¤Ï <netdb.h> Ãæ¤Ç°Ê²¼¤Î¤è¤¦¤ËÄêµÁ¤µ¤ì¤Æ¤¤¤ë:

struct hostent {
        char    *h_name;        /* official name of host */
        char    **h_aliases;    /* alias list */
        int     h_addrtype;     /* host address type */
        int     h_length;       /* length of address */
        char    **h_addr_list;  /* list of addresses */
}
#define h_addr  h_addr_list[0]  /* for backward compatibility */

hostent ¹½Â¤ÂΤΥá¥ó¥Ð¤Ï°Ê²¼¤ÎÄ̤ꡣ

h_name

¥Û¥¹¥È¤ÎÀµ¼°Ì¾ (official name)¡£

h_aliases

¥Û¥¹¥È¤ÎÊÌ̾¤«¤é¤Ê¤ëÇÛÎó¡£ 0 ¤Ç½ªÃ¼¤¹¤ë¡£

h_addrtype

¥¢¥É¥ì¥¹¤Î¥¿¥¤¥×¡£¸½ºß¤Ï¤¹¤Ù¤Æ AF_INET ¤Ç¤¢¤ë¡£

h_length

¥Ð¥¤¥Èñ°Ì¤Çɽ¤·¤¿¥¢¥É¥ì¥¹¤ÎŤµ¡£

h_addr_list

¥Û¥¹¥È¤Î¥Í¥Ã¥È¥ï¡¼¥¯¥¢¥É¥ì¥¹¤ò¥Í¥Ã¥È¥ï¡¼¥¯¥Ð¥¤¥È¥ª¡¼¥À¡¼¤Çɽ¤·¤¿ÇÛÎó¡£ 0 ¤Ç½ªÃ¼¤¹¤ë¡£

h_addr

h_addr_list ¤ÎºÇ½é¤Î¥¢¥É¥ì¥¹¡£²áµî¤È¤Î¸ß´¹À­¤òÊݤĤ¿¤á¤Î¤â¤Î¤Ç¤¢¤ë¡£

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HOST_NOT_FOUND

»ØÄꤷ¤¿¥Û¥¹¥È¤¬¸«¤Ä¤«¤é¤Ê¤¤¡£

NO_ADDRESS ¤Þ¤¿¤Ï NO_DATA

»ØÄꤷ¤¿Ì¾Á°¤ÏÍ­¸ú¤À¤¬ IP ¥¢¥É¥ì¥¹¤ò»ý¤Ã¤Æ¤¤¤Ê¤¤¡£

NO_RECOVERY

¥Í¡¼¥à¥µ¡¼¥Ð¡¼¤ÎÉüµìÉÔǽ¤Ê¥¨¥é¡¼¤¬µ¯¤³¤Ã¤¿¡£

TRY_AGAIN

aurhoritative ¤Ê¥Í¡¼¥à¥µ¡¼¥Ð¡¼¤Ç°ì»þŪ¤Ê¥¨¥é¡¼¤¬µ¯¤³¤Ã¤¿¡£»þ´Ö¤ò¤ª¤¤¤Æ ¤â¤¦°ìÅٻ¤³¤È¡£

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/etc/host.conf

̾Á°²ò·è¤ÎÀßÄê¥Õ¥¡¥¤¥ë

/etc/hosts

¥Û¥¹¥È¤Î¥Ç¡¼¥¿¥Ù¡¼¥¹¥Õ¥¡¥¤¥ë

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SUS-v2 ¤Ï¥Ð¥°¤¬Â¿¤¯¡¢ len ¥Ñ¥é¥á¡¼¥¿¤ò size_t ·¿¤È¤·¤ÆÀë¸À¤·¤Æ¤¤¤ë¡£ (¤³¤ì¤Ï¸í¤ê¤Ç¡¢ size_t ·¿¤Ç¤Ï¤Ê¤¯ int ·¿¤Ç¤Ê¤±¤ì¤Ð¤Ê¤é¤Ê¤¤¡£ Austin ¥É¥é¥Õ¥È¤Ç¤Ï¤³¤ì¤ò socklen_t ¤È¤·¤Æ¤¤¤ë¤¬¡¢¤³¤ì¤Ï OK¡£)

glibc2 ¤Ë¤Ï

struct hostent *gethostbyname2(const char *name, int af);

¤â¤¢¤ê¡¢ gethostbyname() ¤ÈƱ¤¸¤è¤¦¤ËÆ°ºî¤¹¤ë¤¬¡¢ ¤³¤Á¤é¤Ï¥¢¥É¥ì¥¹¤¬Â°¤¹¤ë¥¢¥É¥ì¥¹¥Õ¥¡¥ß¥ê¡¼¤ò»ØÄꤹ¤ë¤³¤È¤¬¤Ç¤­¤ë¡£

Austin ¥É¥é¥Õ¥È¤Ï gethostbyaddr() ¤ª¤è¤Ó gethostbyname() ¤ò²áµî¤Î¤â¤Î¤È¤·¡¢

struct hostent *getipnodebyaddr (const void *restrict addr,
  socklen_t len, int type, int *restrict error_num);

struct hostent *getipnodebyname (const char *name,
  int type, int flags, int *error_num);

¤òƳÆþ¤·¤Æ¤¤¤ë¡£

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