getprotobyname Subroutine

Purpose

Gets protocol entry from the /etc/protocols file by protocol name.

Library

Standard C Library (libc.a)

Syntax

#include <netdb.h>

Description

The getprotobyname subroutine is threadsafe. However, the return value points to static data that is overwritten by subsequent calls. This data must be copied to be saved for use by subsequent calls.

The getprotobyname subroutine retrieves protocol information from the /etc/protocols file by protocol name. An application program can use the getprotobyname subroutine to access a protocol name, its aliases, and protocol number.

The getprotobyname subroutine searches the protocols file sequentially from the start of the file until it finds a matching protocol name or until it reaches the end of the file. The subroutine returns a pointer to a protoent structure, which contains fields for a line of information in the /etc/protocols file. The netdb.h file defines the protoent structure.

Use the endprotoent subroutine to close the /etc/protocols file.

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

Parameters

Return Values

Upon successful completion, the getprotobyname subroutine returns a pointer to a protoent structure.

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