gethostbyname()

The gethostbyname() call tries to resolve the host address to an IP address. The resolution attempted depends on how the resolver is configured and if any local host tables exist. If the symbol RESOLVE_VIA_LOOKUP is defined before including MANIFEST.H, gethostbyname() only uses local host tables and name servers are not used. See z/OS Communications Server: IP Configuration Guide for information about configuring the resolver and using local host tables.

#include <manifest.h>
#include <netdb.h>
struct hostent *gethostbyname(char *name)

Parameter: Description
name: The name of the host being queried. Any trailing blanks will be removed from the specified name prior to trying to resolve it to an IP address. The maximum host name length is 255 characters.

The gethostbyname() call returns a pointer to a hostent structure for the host name specified on the call.

The NETDB.H header file defines the hostent structure and contains the following elements:

Element: Description
h_name: The address of the official name of the host
h_aliases: A pointer to a zero-terminated list of addresses pointing to alternate names for the host
h_addrtype: The type of host address returned; currently, set to AF_INET
h_length: The length of the host address in bytes
h_addr: A pointer to the network address of the host

Return values

The return value points to static data that is overwritten by subsequent calls. A pointer to a hostent structure indicates success. A NULL pointer indicates an error or EOF. When a NULL pointer or 0 is returned, the value of errno is indeterminate, and, therefore, the output from a tcperror() call is also not valid. Global variable h_errno identifies the specific error.

h_errno Value: Description
HOST_NOT_FOUND: The name specified is unknown.
TRY_AGAIN: Temporary error; information not currently accessible.
NO_RECOVERY: Fatal error occurred.

Related calls

gethostent(), sethostent(), endhostent()