gethostbyname, gethostbyname_r - Get a network host entry by name
Standard C Library (libc.so, libc.a)
struct hostent *gethostbyname(
const char *name);
[DIGITAL] The following function is supported in order to maintain backward
compatibility with previous versions of the operating system. You should not use
it in new designs.
const char *name,
struct hostent *hptr,
struct hostent_data *hdptr);
Interfaces documented on this reference page conform to industry standards as follows:
Refer to the standards(5) reference page for more information about industry standards and associated tags.
Specifies the official network name or alias. [DIGITAL] For gethostbyname_r() only, this points to the hostent structure. The netdb.h header file defines hostent structure. [DIGITAL] For gethostbyname_r() only, this is data for hosts database. The netdb.h header file defines hostent_data structure.
The gethostbyname() function returns a pointer to a structure of type hostent. Its members specify data obtained from either the local /etc/hosts file or one of the files distributed by BIND or NIS. To determine which file or files to search, and in which order, the system uses the switches in the /etc/svc.conf file. The netdb.h header file defines the hostent structure.
If using BIND, the information is obtained from a name server specified in the /etc/resolv.conf file.
If the name parameter does not contain a dot "." and you are using BIND, the gethostbyname() function checks whether the environment variable HOSTALIASES is set. If set, it first searches the file named by HOSTALIASES for an alias matching the name parameter. The alias file has the following format: name1 name2 The alias name. This name cannot include dots. The host name used by BIND to look up the host information. The hosts database must be distributed by BIND.
The gethostbyname() function returns a pointer to thread-specific data. Subsequent calls to this or a related function from the same thread overwrite this data.
[DIGITAL] The gethostbyname_r() function is an obsolete reentrant version of the gethostbyname() function. It is supported in order to maintain backward compatibility with previous versions of the operating system and should not be used in new designs. Note that you must zero-fill the hdptr structure before its first access by the gethostbyname_r() function.
Upon successful completion, the gethostbyname() function returns a pointer to a hostent structure. If it reaches the end of the network hostname database, it returns a null pointer.
[DIGITAL] Upon successful completion, the gethostbyname_r() function stores the hostent structure in the location pointed to by hptr, and returns a value of 0 (zero). Upon failure, it returns a value of -1.
If the gethostbyname() or gethostbyname_r() function call fails, h_errno is set to one of the following the values: Host is unknown. The server recognized the request and the name, but no address is available for the name. Another type of name server request may be successful. An unexpected server failure occurred. This is a nonrecoverable error. A transient error occurred, for example, the server did not respond. A retry at some later time may be successful.
[DIGITAL] If any of the following conditions occurs, the gethostbyaddr_r() function sets errno to the corresponding value: The name, hptr, or hdptr is invalid.
The DARPA 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. The resolver configuration file. The database service selection configuration file.
Functions: endhostent(3), gethostbyaddr(3), sethostent(3)
Files: hostname(5), resolv.conf(4), svc.conf(4)
Networks: bind_intro(7), nis_intro(7)
Standards: standards(5) delim off