Mercurial > ecos-v3_0-branch
diff packages/net/tcpip/current/doc/gethost.html @ 97:ced4577552cd ecos-sw-2000-06-06
Merge from eCos master repository on 2000-06-06-08:44:00-BST
| author | jlarmour |
|---|---|
| date | Tue, 06 Jun 2000 08:39:36 +0000 |
| parents | |
| children |
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new file mode 100644 --- /dev/null +++ b/packages/net/tcpip/current/doc/gethost.html @@ -0,0 +1,110 @@ +<html> +<body> +<pre> +NAME + gethostbyname, gethostbyaddr, herror, hstrerror - get network host entry + +SYNOPSIS + #include <network.h> + + struct hostent *gethostbyname(const char *name); + + struct hostent *gethostbyaddr(const char *addr, int len, int type); + + void herror(const char *s); + + const char * hstrerror(int err); + +DESCRIPTION + The gethostbyname() function returns a structure of type + hostent for the given host name. Here name is either a + host name, or an IPv4 address in standard dot notation, or + an IPv6 address in colon (and possibly dot) notation. (See + RFC 1884 for the description of IPv6 addresses.) If name + is an IPv4 or IPv6 address, no lookup is performed and + gethostbyname() simply copies name into the h_name field + and its struct in_addr equivalent into the h_addr_list[0] + field of the returned hostent structure. 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 for + mat.) The current domain and its parents are searched + unless name ends in a dot. + + The gethostbyaddr() function returns a structure of type + hostent for the given host address addr of length len and + address type type. The only valid address type is cur + rently AF_INET. + + The (obsolete) herror() function prints the error message + associated with the current value of h_errno on stderr. + + The (obsolete) hstrerror() function takes an error number + (typically h_errno) and returns the corresponding message + string. + + The domain name queries carried out by gethostbyname() and + gethostbyaddr() use a combination of any or all of the + name server named(8), a broken out line from /etc/hosts, + and the Network Information Service (NIS or YP), depending + upon the contents of the order line in /etc/host.conf. + (See resolv+(8)). The default action is to query + named(8), followed by /etc/hosts. + + The hostent structure is defined in <netdb.h> as follows: + + 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 */ + + The members of the hostent structure are: + + h_name The official name of the host. + + h_aliases + A zero-terminated array of alternative names for + the host. + + h_addrtype + The type of address; always AF_INET at present. + + h_length + The length of the address in bytes. + + h_addr_list + A zero-terminated array of network addresses for + the host in network byte order. + + h_addr The first address in h_addr_list for backward com + patibility. + +RETURN VALUE + The gethostbyname() and gethostbyaddr() functions return + the hostent structure or a NULL pointer if an error + occurs. On error, the h_errno variable holds an error + number. + +ERRORS + The variable h_errno can have the following values: + + HOST_NOT_FOUND + The specified host is unknown. + + NO_ADDRESS or NO_DATA + The requested name is valid but does not have an IP + address. + + NO_RECOVERY + A non-recoverable name server error occurred. + + TRY_AGAIN + A temporary error occurred on an authoritative name + server. Try again later. +</pre> +</body> +</html>