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man pages section 3: Library Interfaces and Headers

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Updated: Thursday, June 13, 2019
 
 

netdb.h(3HEAD)

Name

netdb.h, 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.h(3HEAD).

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

char *h_name          /* official name of the host */
char **h_aliases      /* pointer to an array of pointers to 
                         alternative host names, terminated 
                         by a null pointer */
int  h_addrtype       /* address type */
int  h_length         /* length, in bytes, of the address */
char **h_addr_list    /* 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 network */
char      **n_aliases /* 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     /* pointer to an array of pointers to 
                        alternative protocol names, terminated
                        by a null pointer */
int  p_proto         /* 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     /* pointer to an array of pointers to
                        alternativeservice names, terminated by
                        a null pointer */
int  s_port          /* port number at which the service
                        resides, in network byte order */
char *s_proto        /* 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.h(3HEAD).

Attributes

See attributes(7) for descriptions of the following attributes:

ATTRIBUTE TYPE
ATTRIBUTE VALUE
Interface Stability
Committed
Standard

See Also

endhostent(3C), endhostent(3C), endnetent(3C), endnetent(3C), endprotoent(3C), endprotoent(3C), endservent(3C), endservent(3C), in.h(3HEAD), intro(3), attributes(7), standards(7)