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.TH GETNAMEINFO 3XNET "Nov 1, 2003"
.SH NAME
getnameinfo \- get name information
.SH SYNOPSIS
.LP
.nf
\fBcc\fR [ \fIflag\fR ... ] \fIfile\fR ... [ \fIlibrary\fR ... ]
#include <sys/socket.h>
#include <netdb.h>

\fBint\fR \fBgetnameinfo\fR(\fBconst struct sockaddr *restrict\fR \fIsa\fR, \fBsocklen_t\fR \fIsalen\fR,
     \fBchar *restrict\fR \fInode\fR, \fBsocklen_t\fR \fInodelen\fR, \fBchar *restrict\fR \fIservice\fR,
     \fBsocklen_t\fR \fIservicelen\fR, \fBunsigned\fR \fIflags\fR);
.fi

.SH DESCRIPTION
.LP
The \fBgetnameinfo()\fR function translates a socket address to a node name and
service location, all of which are defined as in \fBgetaddrinfo\fR(3XNET).
.sp
.LP
The \fIsa\fR argument points to a socket address structure to be translated. If
the socket address structure contains an IPv4-mapped IPv6 address or an
IPv4-compatible IPv6 address, the implementation extracts the embedded IPv4
address and lookup the node name for that IPv4 address.
.sp
.LP
If the \fInode\fR argument is non-\fINULL\fR and the nodelen argument is
non-zero, then the \fInode\fR argument points to a buffer able to contain up to
\fInodelen\fR characters that receives the node name as a null-terminated
string. If the \fInode\fR argument is \fINULL\fR or the \fInodelen\fR argument
is zero, the node name is not returned. If the node's name cannot be located,
the numeric form of the node's address is returned instead of its name.
.sp
.LP
If the \fIservice\fR argument is non-\fINULL\fR and the \fIservicelen\fR
argument is non-zero, then the \fIservice\fR argument points to a buffer able
to contain up to \fIservicelen\fR bytes that receives the service name as a
null-terminated string. If the \fIservice\fR argument is \fINULL\fR or the
\fIservicelen\fR argument is zero, the service name is not returned. If the
service's name cannot be located, the numeric form of the service address (for
example, its port number) is returned instead of its name.
.sp
.LP
The \fIflags\fR argument is a flag that changes the default actions of the
function. By default the fully-qualified domain name (FQDN) for the host is
returned, but:
.RS +4
.TP
.ie t \(bu
.el o
If the flag bit \fBNI_NOFQDN\fR is set, only the node name portion of the FQDN
is returned for local hosts.
.RE
.RS +4
.TP
.ie t \(bu
.el o
If the flag bit \fBNI_NUMERICHOST\fR is set, the numeric form of the host's
address is returned instead of its name, under all circumstances.
.RE
.RS +4
.TP
.ie t \(bu
.el o
If the flag bit \fBNI_NAMEREQD\fR is set, an error is returned if the host's
name cannot be located.
.RE
.RS +4
.TP
.ie t \(bu
.el o
If the flag bit \fBNI_NUMERICSERV\fR is set, the numeric form of the service
address is returned (for example, its port number) instead of its name, under
all circumstances.
.RE
.RS +4
.TP
.ie t \(bu
.el o
If the flag bit \fBNI_DGRAM\fR is set, this indicates that the service is a
datagram service (\fBSOCK_DGRAM\fR). The default behavior assumes that the
service is a stream service (\fBSOCK_STREAM\fR).
.RE
.SH RETURN VALUES
.LP
A 0 return value for \fBgetnameinfo()\fR indicates successful completion; a
non-zero return value indicates failure. The possible values for the failures
are listed in the ERRORS section.
.sp
.LP
Upon successful completion, \fBgetnameinfo()\fR returns the node and service
names, if requested, in the buffers provided. The returned names are always
null-terminated strings.
.SH ERRORS
.LP
The \fBgetnameinfo()\fR function will fail if:
.sp
.ne 2
.na
\fB\fBEAI_AGAIN\fR\fR
.ad
.RS 16n
The name could not be resolved at this time. Future attempts might succeed.
.RE

.sp
.ne 2
.na
\fB\fBEAI_BADFLAGS\fR\fR
.ad
.RS 16n
The \fIflags\fR argument had an invalid value.
.RE

.sp
.ne 2
.na
\fB\fBEAI_FAIL\fR\fR
.ad
.RS 16n
A non-recoverable error occurred.
.RE

.sp
.ne 2
.na
\fB\fBEAI_FAMILY\fR\fR
.ad
.RS 16n
The address family was not recognized or the address length was invalid for the
specified family.
.RE

.sp
.ne 2
.na
\fB\fBEAI_MEMORY\fR\fR
.ad
.RS 16n
There was a memory allocation failure.
.RE

.sp
.ne 2
.na
\fB\fBEAI_NONAME\fR\fR
.ad
.RS 16n
The name does not resolve for the supplied parameters.       \fBNI_NAMEREQD\fR
is set and the host's name cannot be located, or both \fInodename\fR and
\fIservname\fR were \fINULL\fR.
.RE

.sp
.ne 2
.na
\fB\fBEAI_SYSTEM\fR\fR
.ad
.RS 16n
A system error occurred. The error code can be found in \fBerrno\fR.
.RE

.SH USAGE
.LP
If the returned values are to be used as part of any further name resolution
(for example, passed to \fBgetaddrinfo()\fR), applications should provide
buffers large enough to store any result possible on the system.
.sp
.LP
Given the IPv4-mapped IPv6 address "::ffff:1.2.3.4", the implementation
performs a lookup as if the socket address structure contains the IPv4 address
"1.2.3.4".
.SH ATTRIBUTES
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE  ATTRIBUTE VALUE
_
Interface Stability     Standard
_
MT-Level        MT-Safe
.TE

.SH SEE ALSO
.LP
\fBsockaddr\fR(3SOCKET),
\fBgai_strerror\fR(3XNET), \fBgetaddrinfo\fR(3XNET),
\fBgetservbyname\fR(3XNET), \fBsocket\fR(3XNET), \fBattributes\fR(5),
\fBstandards\fR(5)
.SH NOTES
.LP
The IPv6 unspecified address ("::") and the IPv6 loopback address ("::1") are
not IPv4-compatible addresses. If the address is the IPv6 unspecified address
("::"), a lookup is not performed, and the \fBEAI_NONAME\fR error is returned.
.sp
.LP
The two \fBNI_NUMERIC\fR\fIxxx\fR flags are required to support the \fB-n\fR
flag that many commands provide.
.sp
.LP
The \fBNI_DGRAM\fR flag is required for the few \fBAF_INET\fR and
\fBAF_INET6\fR port numbers (for example, [512,514]) that represent different
services for UDP and TCP.