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Manual page for netdb(5)

netdb - definitions for network database operations

SYNOPSIS

#include <netdb.h>

DESCRIPTION

The <netdb.h> header defines the type in_port_t and the type in_addr_t as described in in.5

The <netdb.h> header defines the hostent structure that includes the following members:

char   *h_name         Official name of the net.
char   **h_aliases     A pointer to an array of pointers to alternative host names,
                       terminated by a null pointer.
int    h_addrtype      Address type.
int    h_length        The length, in bytes, of the address.
char   **h_addr_list   A pointer to an array of pointers to network addresses (in
                       network byte order) for the host, terminated by a null pointer.

The <netdb.h> header defines the netent structure that includes the following members:

char        *n_name       Official, fully-qualified (including the domain) name of the host.
char        **n_aliases   A pointer to an array of pointers to alternative network names,
                          terminated by a null pointer.
int         n_addrtype    The address type of the network.
in_addr_t   n_net         The network number, in host byte order.

The <netdb.h> header defines the protoent structure that includes the following members:

char   *p_name       Official name of the protocol.
char   **p_aliases   A pointer to an array of pointers to alternative protocol names,
                     terminated by a null pointer.
int    p_proto       The protocol number.

The <netdb.h> header defines the servent structure that includes the following members:

char   *s_name       Official name of the service.
char   **s_aliases   A pointer to an array of pointers to alternative service names,
                     terminated by a null pointer.
int    s_port        The port number at which the service resides, in network byte order.
char   *s_proto      The name of the protocol to use when contacting the service.

The <netdb.h> header defines the macro IPPORT_RESERVED with the value of the highest reserved Internet port number.

The <netdb.h> header provides a declaration for h_errno:

: extern int h_errno;

The <netdb.h> header defines the following macros for use as error values for gethostbyaddr() and gethostbyname():

HOST_NOT_FOUND   NO_DATA
NO_RECOVERY      TRY_AGAIN

Inclusion of the <netdb.h> header may also make visible all symbols from in.5

Default

For applications that do not require standard-conforming behavior (those that use the socket interfaces described in section 3N of the reference manual; see Intro.3 and standards.5 the following are declared as functions, and may also be defined as macros:

int               endhostent(void);
int               endnetent(void);
int               endprotoent(void);
int               endservent(void);
struct hostent    *gethostbyaddr(const void *addr, int len, int type);
struct hostent    *gethostbyname(const char *name);
struct hostent    *gethostent(void);
struct netent     *getnetbyaddr(long net, int type);
struct netent     *getnetbyname(const char *name);
struct netent     *getnetent(void);
struct protoent   *getprotobyname(const char *name);
struct protoent   *getprotobynumber(int proto);
struct protoent   *getprotoent(void);
struct servent    *getservbyname(const char *name, const char *proto);
struct servent    *getservbyport(int port, const char *proto);
struct servent    *getservent(void);
int               sethostent(int stayopen);
int               setnetent(int stayopen);
int               setprotoent(int stayopen);
int               setservent(int stayopen);

Standard-conforming

For applications that require standard-conforming behavior (those that use the socket interfaces described in section 3XN of the reference manual; see Intro.3 and standards.5 the following are declared as functions, and may also be defined as macros:

void              endhostent(void);
void              endnetent(void);
void              endprotoent(void);
void              endservent(void);
struct hostent    *gethostbyaddr(const void *addr, size_t len, int type);
struct hostent    *gethostbyname(const char *name);
struct hostent    *gethostent(void);
struct netent     *getnetbyaddr(in_addr_t net, int type);
struct netent     *getnetbyname(const char *name);
struct netent     *getnetent(void);
struct protoent   *getprotobyname(const char *name);
struct protoent   *getprotobynumber(int proto);
struct protoent   *getprotoent(void);
struct servent    *getservbyname(const char *name, const char *proto);
struct servent    *getservbyport(int port, const char *proto);
struct servent    *getservent(void);
void              sethostent(int stayopen);
void              setnetent(int stayopen);
void              setprotoent(int stayopen);
void              setservent(int stayopen);

netdb - definitions for network database operations

SYNOPSIS

DESCRIPTION

Default

Standard-conforming

SEE ALSO