gethostent.3n (2010 09)

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gethostent(3N) gethostent(3N)

NAME

gethostent(), gethostbyaddr(), gethostbyname(), sethostent(), endhostent() - get, set, or end network host

entry

SYNOPSIS

#include <sys/socket.h>

#include <netinet/in.h>

#include <netdb.h>

struct hostent *gethostent(void);

struct hostent *gethostbyname(const char *name);

struct hostent *gethostbyaddr(const char *addr,

int len,

int type);

_XOPEN_SOURCE_EXTENDED only

struct hostent *gethostbyaddr(const void *addr,

size_t len,

int type);

int sethostent(int stayopen);

int endhostent(void);

_XOPEN_SOURCE_EXTENDED only

void sethostent(int stayopen);

void endhostent(void);

DESCRIPTION

The gethostent(), gethostbyname()

, and gethostbyaddr() functions 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.

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 net-

work address per host.

Name Service Switch-Based Operation

These host entry library routines internally call the name service switch to access the "hosts" database

lookup policy conﬁgured in the

/etc/nsswitch.conf ﬁle (see nsswitch.conf(4)). The lookup policy

deﬁnes the order and the criteria of the supported name services used to resolve host names and Internet

addresses. The operations of these name services: Domain Name Server, NIS, and nonserver mode (e.g.,

ﬁles) are listed below.

Domain Name Server Operation

If the local system is conﬁgured to use the

named name server (see named(1M) and resolver (4)) for name

or address resolution, then the function:

HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

Summary of content (6 pages)

PAGE 1
gethostent(3N) gethostent(3N) NAME gethostent(), gethostbyaddr(), gethostbyname(), sethostent(), endhostent() - get, set, or end network host entry SYNOPSIS #include #include #include
PAGE 2
gethostent(3N) gethostent(3N) 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() gethostbyaddr() Each retrieves host information from the name server. Names are matched without respect to uppercase or lowercase. For example, berkeley.
PAGE 3
gethostent(3N) gethostent(3N) byteorder (3N)) and the header file ). 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 structure. gethostbyname() and gethostbyaddr() return NULL if their host or addr parameters, respectively, cannot be found in the database.
PAGE 4
gethostent(3N) gethostent(3N) hp=gethostbyaddr((char *) &addr, sizeof (addr), AF_INET); if (hp == NULL) { (void) printf("host information for %s no found \n", argv[1]); exit (3); } for (p = hp->h_addr_list; *p!=0;p++){ struct in_addr in; char **q; (void)memcpy(&in.s_addr, *p, sizeof(in.
PAGE 5
gethostent(3N) gethostent(3N) STANDARDS CONFORMANCE gethostent(): XPG4 A HP-UX 11i Version 3: September 2010 −5− Hewlett-Packard Company 5 gA
PAGE 6
(Notes) A (Notes) gA 6 Hewlett-Packard Company −1− HP-UX 11i Version 3: September 2010