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Technical Reference: Communications, Volume 2

getnetbyaddr Subroutine


Gets network entry by address.


Standard C Library (libc.a)


#include <netdb.h>

struct netent *getnetbyaddr ( Network, Type)
long Network;
int Type;


Attention: Do not use the getnetbyaddr subroutine in a multithreaded environment.

The getnetbyaddr subroutine retrieves information from the /etc/networks file using the network address as a search key. The getnetbyaddr subroutine searches the file sequentially from the start of the file until it encounters a matching net number and type or until it reaches the end of the file.

The getnetbyaddr subroutine returns a pointer to a netent structure, which contains the equivalent fields for a network description line in the /etc/networks file. The netent structure is defined in the netdb.h file.

Use the endnetent subroutine to close the /etc/networks file.


Network Specifies the number of the network to be located.
Type Specifies the address family for the network. The only supported value is AF_INET.

Return Values

Upon successful completion, the getnetbyaddr subroutine returns a pointer to a netent structure.

Note: The return value points to static data that is overwritten by subsequent calls.

If an error occurs or the end of the file is reached, the getnetbyaddr subroutine returns a null pointer.

Implementation Specifics

The getnetbyaddr subroutine is part of Base Operating System (BOS) Runtime.

All applications containing the getnetbyaddr subroutine must be compiled with _BSD set to a specific value. Acceptable values are 43 and 44. In addition, all socket applications must include the BSD libbsd.a library.


                          Contains official network names.

Related Information

The endnetent subroutine, getnetbyname subroutine, getnetent subroutine, setnetent subroutine.

Sockets Overview in AIX 5L Version 5.1 General Programming Concepts: Writing and Debugging Programs.

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