Gets a protocol entry from the /etc/protocols file by number.
#include <netdb.h>
struct protoent *getprotobynumber ( Protocol)
int Protocol;
Attention: Do not use the getprotobynumber subroutine in a multithreaded environment.
The getprotobynumber subroutine retrieves protocol information from the /etc/protocols file using a specified protocol number as a search key. An application program can use the getprotobynumber subroutine to access a protocol name, its aliases, and protocol number.
The getprotobynumber subroutine searches the /etc/protocols file sequentially from the start of the file until it finds a matching protocol name or protocol number, 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.
| Protocol | Specifies the protocol number. |
Upon successful completion, the getprotobynumber subroutine, returns a pointer to a protoent 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 getprotobynumber subroutine returns a null pointer.
The getprotobynumber subroutine is part of Base Operating System (BOS) Runtime.
All applications containing the getprotobynumber 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.
| /etc/protocols | |
| Contains protocol information. | |
The endprotoent subroutine, getprotobyname subroutine, getprotoent subroutine, setprotoent subroutine.
Sockets Overview in AIX 5L Version 5.1 Communications Programming Concepts.