getprotobynumber(3)getprotobynumber(3)NAME
getprotobynumber, getprotobynumber_r - Get a protocol entry by number
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 operating
system. You should not use it in new designs. int getprotobynumber_r(
int num,
struct protoent *proto,
struct protoent_data *proto_data );
LIBRARY
Standard C Library (libc)
STANDARDS
Interfaces documented on this reference page conform to industry stan‐
dards as follows:
getprotobyname(): XNS4.0, XNS5.0
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 proto‐
cols 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() func‐
tion 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 reen‐
trant 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 getproto‐
bynumber() function.
[Tru64 UNIX] If any of the following conditions occurs, the getproto‐
bynumber_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 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.
SEE ALSO
Functions: getprotobyname(3), getprotoent(3), setprotoent(3), endpro‐
toent(3).
Files: protocols(4), svc.conf(4).
Networks: nis_intro(7).
Standards: standards(5).
Network Programmer's Guide
getprotobynumber(3)