SYNOPSIS<\/a>
DESCRIPTION<\/a>
RETURN VALUE<\/a>
FILES<\/a>
VERSIONS<\/a>
ATTRIBUTES<\/a>
CONFORMING TO<\/a>
NOTES<\/a>
EXAMPLES<\/a>
SEE ALSO<\/a>
COLOPHON<\/a> <\/p>\n
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NAME <\/a> <\/h2>\ngetnameinfo \u2212 address-to-name translation in protocol-independent manner<\/p>\n
SYNOPSIS <\/a> <\/h2>\n#include
#include <\/b><\/p>\nint getnameinfo(const struct sockaddr *<\/b>addr<\/i>, socklen_t<\/b> addrlen<\/i>,
char *<\/b>host<\/i>, socklen_t<\/b> hostlen<\/i>,
char *<\/b>serv<\/i>, socklen_t<\/b> servlen<\/i>, int<\/b> flags<\/i>);<\/b><\/p>\n
Feature Test Macro Requirements for glibc (see feature_test_macros<\/b>(7)):<\/p>\n
getnameinfo<\/b>():
Since glibc 2.22: _POSIX_C_SOURCE >= 200112L
Glibc 2.21 and earlier: _POSIX_C_SOURCE<\/p>\nDESCRIPTION <\/a> <\/h2>\nThe getnameinfo<\/b>() function is the inverse of getaddrinfo<\/b>(3): it converts a socket address to a corresponding host and service, in a protocol-independent manner. It combines the functionality of gethostbyaddr<\/b>(3) and getservbyport<\/b>(3), but unlike those functions, getnameinfo<\/b>() is reentrant and allows programs to eliminate IPv4-versus-IPv6 dependencies.<\/p>\n
The addr<\/i> argument is a pointer to a generic socket address structure (of type sockaddr_in<\/i> or sockaddr_in6<\/i>) of size addrlen<\/i> that holds the input IP address and port number. The arguments host<\/i> and serv<\/i> are pointers to caller-allocated buffers (of size hostlen<\/i> and servlen<\/i> respectively) into which getnameinfo<\/b>() places null-terminated strings containing the host and service names respectively.<\/p>\n
The caller can specify that no hostname (or no service name) is required by providing a NULL host<\/i> (or serv<\/i>) argument or a zero hostlen<\/i> (or servlen<\/i>) argument. However, at least one of hostname or service name must be requested.<\/p>\n
The flags<\/i> argument modifies the behavior of getnameinfo<\/b>() as follows:
NI_NAMEREQD<\/b><\/p>\n
If set, then an error is returned if the hostname cannot be determined.<\/p>\n
NI_DGRAM<\/b><\/p>\n
If set, then the service is datagram (UDP) based rather than stream (TCP) based. This is required for the few ports (512\u2013514) that have different services for UDP and TCP.<\/p>\n
NI_NOFQDN<\/b><\/p>\n
If set, return only the hostname part of the fully qualified domain name for local hosts.<\/p>\n
NI_NUMERICHOST<\/b><\/p>\n
If set, then the numeric form of the hostname is returned. (When not set, this will still happen in case the node\u2019s name cannot be determined.)<\/p>\n
NI_NUMERICSERV<\/b><\/p>\n
If set, then the numeric form of the service address is returned. (When not set, this will still happen in case the service\u2019s name cannot be determined.)<\/p>\n
Extensions to getnameinfo() for Internationalized Domain Names<\/b>
Starting with glibc 2.3.4, getnameinfo<\/b>() has been extended to selectively allow hostnames to be transparently converted to and from the Internationalized Domain Name (IDN) format (see RFC 3490, Internationalizing Domain Names in Applications (IDNA)<\/i>). Three new flags are defined:<\/p>\n
#include int getnameinfo(const struct sockaddr *<\/b>addr<\/i>, socklen_t<\/b> addrlen<\/i>, Feature Test Macro Requirements for glibc (see feature_test_macros<\/b>(7)):<\/p>\n getnameinfo<\/b>(): The getnameinfo<\/b>() function is the inverse of getaddrinfo<\/b>(3): it converts a socket address to a corresponding host and service, in a protocol-independent manner. It combines the functionality of gethostbyaddr<\/b>(3) and getservbyport<\/b>(3), but unlike those functions, getnameinfo<\/b>() is reentrant and allows programs to eliminate IPv4-versus-IPv6 dependencies.<\/p>\n The addr<\/i> argument is a pointer to a generic socket address structure (of type sockaddr_in<\/i> or sockaddr_in6<\/i>) of size addrlen<\/i> that holds the input IP address and port number. The arguments host<\/i> and serv<\/i> are pointers to caller-allocated buffers (of size hostlen<\/i> and servlen<\/i> respectively) into which getnameinfo<\/b>() places null-terminated strings containing the host and service names respectively.<\/p>\n The caller can specify that no hostname (or no service name) is required by providing a NULL host<\/i> (or serv<\/i>) argument or a zero hostlen<\/i> (or servlen<\/i>) argument. However, at least one of hostname or service name must be requested.<\/p>\n The flags<\/i> argument modifies the behavior of getnameinfo<\/b>() as follows: If set, then an error is returned if the hostname cannot be determined.<\/p>\n NI_DGRAM<\/b><\/p>\n If set, then the service is datagram (UDP) based rather than stream (TCP) based. This is required for the few ports (512\u2013514) that have different services for UDP and TCP.<\/p>\n NI_NOFQDN<\/b><\/p>\n If set, return only the hostname part of the fully qualified domain name for local hosts.<\/p>\n NI_NUMERICHOST<\/b><\/p>\n If set, then the numeric form of the hostname is returned. (When not set, this will still happen in case the node\u2019s name cannot be determined.)<\/p>\n NI_NUMERICSERV<\/b><\/p>\n If set, then the numeric form of the service address is returned. (When not set, this will still happen in case the service\u2019s name cannot be determined.)<\/p>\n Extensions to getnameinfo() for Internationalized Domain Names<\/b>
#include
char *<\/b>host<\/i>, socklen_t<\/b> hostlen<\/i>,
char *<\/b>serv<\/i>, socklen_t<\/b> servlen<\/i>, int<\/b> flags<\/i>);<\/b><\/p>\n
Since glibc 2.22: _POSIX_C_SOURCE >= 200112L
Glibc 2.21 and earlier: _POSIX_C_SOURCE<\/p>\nDESCRIPTION <\/a> <\/h2>\n
NI_NAMEREQD<\/b><\/p>\n
Starting with glibc 2.3.4, getnameinfo<\/b>() has been extended to selectively allow hostnames to be transparently converted to and from the Internationalized Domain Name (IDN) format (see RFC 3490, Internationalizing Domain Names in Applications (IDNA)<\/i>). Three new flags are defined:<\/p>\n
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