HPUX gethostent[3n]
gethostent(3N) gethostent(3N)
NAME
gethostent(), gethostbyaddr(), gethostbyname(), sethostent(),
endhostent() - get network host entry
SYNOPSIS
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
extern int h_errno;
struct hostent *gethostent(void);
struct hostent *gethostbyname(const char *name);
struct hostent *gethostbyaddr(
const char *addr,
int len,
int type);
int sethostent(int stayopen);
int endhostent(void);
DESCRIPTION
gethostent(), gethostbyname(), and gethostbyaddr() each return a
pointer to a structure of type hostent, defined as follows in
<netdb.h>:
struct hostent {
char *h_name;
char **h_aliases;
int h_addrtype;
int h_length;
char **h_addr_list;
};
#define h_addr h_addr_list[0]
The members of this structure are:
h_name The official name of the host.
h_aliases A null-terminated array of alternate names
for the host.
h_addrtype The type of address being returned; always
AF_INET.
h_length The length, in bytes, of the address.
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gethostent(3N) gethostent(3N)
h_addr_list A null-terminated array of network addresses
for the host.
h_addr The first address in h_addr_list; this is for
compatibility with previous HP-UX
implementations where a struct hostent
contains only one network address per host.
Name Server Operation
If the local system is configured to use the named name server (see
named(1M)):
gethostent() Always returns a NULL pointer.
sethostent(), Requests the use of a connected stream
socket for queries to the name server if
the stayopen flag is non-zero. The
connection is retained after each call to
gethostbyname() or gethostbyaddr().
endhostent() Closes the stream socket connection.
gethostbyname() Each retrieves host information from the
gethostbyaddr() name server. Names are matched without
respect to uppercase or lowercase. For
example, berkeley.edu, Berkeley.EDU , and
BERKELEY.EDU all match the entry for
berkeley.edu.
NIS Server Operation
If the local system is not configured to use the name server, but is
running ypserv, the Network Information Service server:
gethostent() Returns the next entry in the NIS
database.
sethostent() Initializes an internal key for the NIS
database. If the stayopen flag is non-
zero, the internal key is not cleared
after calls to endhostent().
endhostent() Clears the internal NIS database key.
gethostbyname() Each retrieves host information from the
gethostbyaddr() NIS database. Names are matched without
respect to uppercase or lowercase. For
example, berkeley.edu, Berkeley.EDU , and
BERKELEY.EDU all match the entry for
berkeley.edu.
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gethostent(3N) gethostent(3N)
Non-Server Operation
If the local system is using neither the local name server nor the
Network Information Service server:
gethostent() Reads the next line of /etc/hosts, opening
the file if necessary.
sethostent() opens and rewinds the file. If the
stayopen flag is non-zero, the host data
base is not closed after each call to
gethostent() (either directly or
indirectly through one of the other
gethost calls).
endhostent() Closes the file.
gethostbyname() Sequentially searches from the beginning
of the file until a host name (among
either the official names or the aliases)
matching its name parameter is found, or
until EOF is encountered. Names are
matched without respect to uppercase or
lowercase, as described above in the name
server case.
gethostbyaddr() Sequentially searches from the beginning
of the file until an Internet address
matching its addr parameter is found, or
until EOF is encountered.
In calls to gethostbyaddr(), the parameter addr must point to an
Internet address in network order (see byteorder(3N)). The parameter
len must be the number of bytes in an Internet address; that is,
sizeof (struct in_addr). The parameter type must be the constant
AF_INET.
RETURN VALUE
If successful, gethostbyname(), gethostbyaddr() and gethostent()
return a pointer to the requested hostent struct. gethostbyname() and
gethostbyaddr() return NULL if their host or addr parameters,
respectively, cannot be found in the database. If /etc/hosts is being
used, they also return NULL if they are unable to open /etc/hosts.
gethostbyaddr() also returns NULL if either its addr or len parameter
is invalid. gethostent() always returns NULL if the name server is
being used.
ERRORS
If the name server is being used and gethostbyname() or
gethostbyaddr() returns a NULL pointer, the external integer h_errno
contains one of the following values:
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gethostent(3N) gethostent(3N)
HOST_NOT_FOUND No such host is known.
TRY_AGAIN This is usually a temporary error. The
local server did not receive a response
from an authoritative server. A retry at
some later time may succeed.
NO_RECOVERY This is a non-recoverable error.
NO_ADDRESS The requested name is valid but does not
have an IP address; this is not a
temporary error. This means another type
of request to the name server will result
in an answer.
If the name server is not being used, the value of h_errno may not be
meaningful.
WARNINGS
All information is contained in a static area so it must be copied if
it is to be saved.
AUTHOR
gethostent() was developed by the University of California, Berkeley.
FILES
/etc/hosts
SEE ALSO
named(1M), ypserv(1M), resolver(3N), ypclnt(3C), hosts(4), ypfiles(4).
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