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getnameinfo(3)
NAME
  getnameinfo - Get a node name and service name for an address and port
  number

LIBRARY
  Standard C Library (libc.so, libc.a)

SYNOPSIS
  #include <netdb.h>

  int getnameinfo(
	  const struct sockaddr *sa,
	  socklen_t salen,
	  char *host,
	  size_t *hostlen,
	  char *serv,
	  size_t servlen,
	  int flags);

PARAMETERS
  sa	    Points either to a sockaddr_in structure (for IPv4) or to a
	    sockaddr_in6 structure (for IPv6) that holds the IP address and
	    port number.

  salen	    Specifies the length of either the sockaddr_in structure or the
	    sockaddr_in6 structure.

  host	    Points to a buffer in which to receive the null-terminated
	    network node name or alias corresponding to the address contained
	    in sa.

  hostlen   Specifies the length of the host buffer.  A value of zero
	    instructs the routine not to return a host name.

  serv	    Points to a buffer in which to receive the null-terminated
	    network service name associated with the port number contained in
	    sa.

  servlen   Specifies the length of the serv buffer.  A value of zero
	    instructs the routine not to return a service name.

  flags	    Specifies to change the routine's the default actions.  By
	    default, the routine searches for the fully-qualified domain name
	    of the node in the hosts database and returns it.  See the
	    "Description" section for additional flags.




DESCRIPTION
  The getnameinfo() routine looks up an IP address and port number in a
  sockaddr structure specified by sa and returns node name and service name
  text strings in the buffers pointed to by the host and serv parameters,
  respectively.

  The application must provide buffers large enough to hold the fully-
  qualified domain name and the service name, including the terminating null
  characters.  To assist in initializing the buffers, the following constants
  are defined in <netdb.h>:

       #define NI_MAXHOST  1025
       #define NI_MAXSERV    32

  Flag Bits


  The following flag bits are defined:

  NI_NOFQDN
      If set, the getnameinfo routine returns the node name portion of the
      fully-qualified domain name for local hosts.

  NI_NUMERICHOST
      If set, or if the host's name cannot be located in the hosts database,
      the routine returns the numeric form of the host's address is instead
      of its name.  For example, by calling inet_ntop() instead of
      gethostbyaddr().

  NI_NAMEREQD
      If set, the routine returns an error if the host's name cannot be
      located in the hosts database.

  NI_NUMERICSERV
      If set, the routine returns the numeric form (port number) of the
      service address instead of its name.

  NI_DGRAM
      If set, specifies that the service is a datagram service.	 The
      getnameinfo routine calls getservbyport() with the proto parameter set
      to udp instead of tcp (the default).  This is required for the few
      ports (512-514) that have different services for UDP and TCP.

  The two NI_NUMERIC* flags are required to support the -n flag that many
  commands provide.  All flags are defined in <netdb.h> header file.

RETURN VALUES
  Upon successful completion, the getnameinfo() function returns 0 (zero).
  Upon failure, it returns a non-zero value.

FILES
  /etc/hosts
	    The Internet network hostname database. Each record in the file
	    occupies a single line and has three fields consisting of the
	    host address, official hostname, and aliases.

  /etc/resolv.conf
	    The resolver configuration file.

  /etc/svc.conf
	    The database service selection configuration file.


RELATED INFORMATION
  Functions: endhostent(3), freeaddrinfo(3), gai_strerror(3), getaddrinfo(3),
  gethostbyaddr(3), sethostent(3).


  Files: hostname(5), resolv.conf(4), svc.conf(4).

  Networks: bind_intro(7), nis_intro(7).

Index for Section 3

Alphabetical listing for G

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