version 2, including all changes.
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GETHOSTBYNAME |
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!!!GETHOSTBYNAME |
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NAME |
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SYNOPSIS |
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DESCRIPTION |
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RETURN VALUE |
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ERRORS |
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FILES |
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CONFORMING TO |
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NOTES |
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SEE ALSO |
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---- |
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!!NAME |
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gethostbyname, gethostbyaddr, sethostent, endhostent, herror, hstrerror - get network host entry |
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!!SYNOPSIS |
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__#include |
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__''name''__); |
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struct hostent *gethostbyname2(const char *__''name''__, int__ ''af''__); |
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#include |
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__''addr''__, |
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int__ ''len''__, int__ ''type''__); |
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void sethostent(int__ ''stayopen''__); |
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void endhostent(void); |
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void herror(const char *__''s''__); |
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const char * hstrerror(int__ ''err''__); |
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__ |
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!!DESCRIPTION |
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The __gethostbyname()__ function returns a structure of |
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type ''hostent'' for the given host ''name''. Here |
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''name'' is either a host name, or an IPv4 address in |
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standard dot notation, or an IPv6 address in colon (and |
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possibly dot) notation. (See RFC 1884 for the description of |
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IPv6 addresses.) If ''name'' is an IPv4 or IPv6 address, |
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no lookup is performed and __gethostbyname__() simply |
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copies ''name'' into the ''h_name'' field and its |
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''struct in_addr'' equivalent into the |
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''h_addr_list[[0]'' field of the returned ''hostent'' |
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structure. If ''name'' doesn't end in a dot and the |
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environment variable __HOSTALIASES__ is set, the alias |
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file pointed to by __HOSTALIASES__ will first be searched |
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for ''name'' (see hostname(7) for the file |
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format). The current domain and its parents are searched |
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unless ''name'' ends in a dot. |
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The __gethostbyaddr()__ function returns a structure of |
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type ''hostent'' for the given host address ''addr'' |
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of length ''len'' and address type ''type''. The only |
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valid address type is currently __AF_INET__. |
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The __sethostent()__ function specifies, if |
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''stayopen'' is true (1), that a connected TCP socket |
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should be used for the name server queries and that the |
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connection should remain open during successive queries. |
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Otherwise, name server queries will use UDP |
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datagrams. |
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The __endhostent()__ function ends the use of a TCP |
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connection for name server queries. |
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The (obsolete) __herror()__ function prints the error |
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message associated with the current value of ''h_errno'' |
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on stderr. |
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The (obsolete) __hstrerror()__ function takes an error |
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number (typically ''h_errno'') and returns the |
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corresponding message string. |
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The domain name queries carried out by |
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__gethostbyname()__ and __gethostbyaddr()__ use a |
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combination of any or all of the name server |
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named(8), a broken out line from ''/etc/hosts'', |
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and the Network Information Service (NIS or YP), depending |
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upon the contents of the ''order'' line in |
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''/etc/host.conf''. (See resolv+(8)). The default |
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action is to query named(8), followed by |
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''/etc/hosts''. |
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The ''hostent'' structure is defined in |
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'''' as follows: |
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struct hostent { |
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char *h_name; /* official name of host */ |
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char **h_aliases; /* alias list */ |
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int h_addrtype; /* host address type */ |
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int h_length; /* length of address */ |
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char **h_addr_list; /* list of addresses */ |
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} |
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#define h_addr h_addr_list[[0] /* for backward compatibility */ |
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The members of the ''hostent'' structure |
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are: |
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''h_name'' |
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The official name of the host. |
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''h_aliases'' |
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A zero-terminated array of alternative names for the |
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host. |
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''h_addrtype'' |
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The type of address; always __AF_INET__ at |
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present. |
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''h_length'' |
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The length of the address in bytes. |
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''h_addr_list'' |
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A zero-terminated array of network addresses for the host in |
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network byte order. |
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''h_addr'' |
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The first address in ''h_addr_list'' for backward |
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compatibility. |
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!!RETURN VALUE |
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The __gethostbyname()__ and __gethostbyaddr()__ |
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functions return the ''hostent'' structure or a NULL |
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pointer if an error occurs. On error, the ''h_errno'' |
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variable holds an error number. |
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!!ERRORS |
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The variable ''h_errno'' can have the following |
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values: |
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__HOST_NOT_FOUND__ |
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The specified host is unknown. |
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__NO_ADDRESS__ or __NO_DATA__ |
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The requested name is valid but does not have an IP |
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address. |
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__NO_RECOVERY__ |
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A non-recoverable name server error occurred. |
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__TRY_AGAIN__ |
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A temporary error occurred on an authoritative name server. |
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Try again later. |
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!!FILES |
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''/etc/host.conf'' |
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resolver configuration file |
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''/etc/hosts'' |
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host database file |
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!!CONFORMING TO |
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BSD 4.3. |
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!!NOTES |
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The functions __gethostbyname__() and |
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__gethostbyaddr__() may return pointers to static data, |
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which may be overwritten by later calls. Copying the |
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''struct hostent'' does not suffice, since it contains |
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pointers - a deep copy is required. |
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The SUS-v2 standard is buggy and declares the ''len'' |
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parameter to be of type ''size_t''. (That is wrong, |
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because it has to be ''int'', and ''size_t'' is not. |
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The Austin draft makes it ''socklen_t'', which is |
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OK.) |
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Glibc2 also has a |
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__struct hostent *gethostbyname2(const char *__''name''__, int__ ''af''__); |
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__that works like __gethostbyname()__, but permits to specify the address family to which the address must belong. |
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The Austin draft marks __gethostbyaddr()__ and |
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__gethostbyname()__ legacy, and introduces |
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__struct hostent *getipnodebyaddr (const void *restrict__ ''addr''__, |
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socklen_t__ ''len''__, int__ ''type''__, int *restrict__ ''error_num''__); |
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struct hostent *getipnodebyname (const char *__''name''__, |
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int__ ''type''__, int__ ''flags''__, int *__''error_num''__); |
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__ |
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!!SEE ALSO |
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238 |
resolver(3), hosts(5), hostname(7), |
2 |
perry |
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resolv+(8), named(8) |
1 |
perry |
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---- |