gethostbyname_r()

Get a network host entry, given a name

Synopsis:

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>

struct hostent * gethostbyname_r( const char * name,
                                  struct hostent * result,
                                  char * buffer,
                                  int bufflen,
                                  int * h_errnop );

Description:

The gethostbyname_r() function is a thread-safe version of gethostbyname(). This function gets the network host entry for the host specified by name.

The host entry is returned in the struct hostent pointed to by result. During the operation, buffer (and char buffer of at least buflen bytes) is used to store host database entries; buffer should be large enough to hold all of the data associated with the host entry. A 2K buffer is usually more than enough; a 256 byte buffer is safe in most cases.

The int pointed to by h_errnop is set to an herrno value if an error occurs.

Returns:

A pointer to result, or NULL if an error occurs.

Errors:

If an error occurs, the int pointed to by h_errnop is set to:

ERANGE: The supplied buffer isn't large enough to store the result.
HOST_NOT_FOUND: Authoritative answer: Unknown host.
NO_ADDRESS: No address associated with name; look for an MX record.
NO_DATA: Valid name, but no data record of the requested type. The name is known to the name server, but has no IP address associated with it-this isn't a temporary error. Another type of request to the name server using this domain name will result in an answer (e.g. a mail-forwarder may be registered for this domain).
NO_RECOVERY: Unknown server error. An unexpected server failure was encountered. This is a nonrecoverable network error.
TRY_AGAIN: Nonauthoritative answer: Host name lookup failure. This is usually a temporary error and means that the local server didn't receive a response from an authoritative server. A retry at some later time may succeed.

Files:

/etc/hosts: Local host database file.
/etc/resolv.conf: Resolver configuration file.

Classification:

Unix

Safety:
Interrupt handler	No
Signal handler	No
Thread	Yes