getprotobynumber(3) Library Functions Manual getprotobynumber(3)
NAME
getprotobynumber, getprotobynumber_r - Get a protocol entry by number
LIBRARY
Standard C Library (libc.so, libc.a)
SYNOPSIS
#include <netdb.h>
struct protoent *getprotobynumber( int num);
[Tru64 UNIX] The following obsolete function is supported in order to maintain backward compatibility with previous versions of the oper-
ating system. You should not use it in new designs. int getprotobynumber_r( int num, struct protoent *proto, struct pro-
toent_data *proto_data);
STANDARDS
Interfaces documented on this reference page conform to industry standards as follows:
getprotobyname(): XNS4.0
Refer to the standards(5) reference page for more information about industry standards and associated tags.
PARAMETERS
Specifies the protocol number.
[Tru64 UNIX] For getprotobynumber_r() only, this points to the protoent structure. The netdb.h header file defines the protoent
structure. [Tru64 UNIX] For getprotobynumber_r() only, this is data for the protocols database. The netdb.h header file defines
the protoent_data structure.
DESCRIPTION
The getprotobynumber() function returns a pointer to a structure of type protoent. Its members specify data in fields from a record line in
either the local /etc/protocols file or NIS distributed network protocols database file. 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 protoent structure.
The getprotobynumber() function searches the network protocols database file sequentially until a match with the num parameter occurs. The
num parameter must specify the official protocol number. When EOF (End-Of-File) is reached without a match, a null pointer is returned by
this function.
When using the getprotobynumber() function, use the endprotoent() function to close the protocols file.
NOTES
The getprotobynumber() function returns a pointer to thread-specific data. Subsequent calls to this or a related function from the same
thread overwrite this data.
[Tru64 UNIX] The getprotobynumber_r() function is an obsolete reentrant version of the getprotobynumber() 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 proto_data structure before its first access by either the setprotoent_r() or getprotobynumber_r() functions.
RETURN VALUES
Upon successful completion, the getprotobynumber() function returns a pointer to a protoent structure. If it fails or reaches the end of
the network protocols database file, it returns a null pointer.
[Tru64 UNIX] Upon successful completion, the getprotobynumber_r() function stores the protoent structure in the location pointed to by
proto, and returns a value of 0 (zero). Upon failure, it returns a value of -1.
ERRORS
Current industry standards do not define error values for the getprotobynumber() function.
[Tru64 UNIX] If any of the following conditions occurs, the getprotobynumber_r() function sets errno to the corresponding value:
The proto_data or proto parameter is invalid. The search failed.
In addition, if the getprotobynumber() or getprotobynumber_r() function fails to open the file, it sets errno to indicate the cause of the
failure.
FILES
The DARPA Internet network protocols name database file. Each record in the file occupies a single line and has three fields: the official
protocol name, the protocol number, and protocol aliases. The database service selection configuration file.
RELATED INFORMATION
Functions: getprotobyname(3), getprotoent(3), setprotoent(3), endprotoent(3).
Files: protocols(4), svc.conf(4).
Networks: nis_intro(7).
Standards: standards(5). delim off
getprotobynumber(3)