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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); [Digital] 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); PARAMETERS Specifies the protocol number. [Digital] For getprotobynumber_r() only, this points to the protoent structure. The netdb.h header file defines the pro- toent structure. [Digital] For getprotobynumber_r() only, this is data for the protocols database. The netdb.h header file de- fines 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. [Digital] 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 oper- ating 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. [Digital] Upon successful completion, the getprotobynumber_r() func- tion 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. [Digital] 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 DARPA Internet network protocols name database file. Each record in the file occupies a single line and has three fields: the official pro- tocol name, the protocol number, and protocol aliases. The database service selection configuration file. RELATED INFORMATION Functions: getprotobyname(3), getprotoent(3), setprotoent(3), endpro- toent(3). Files: protocols(4), svc.conf(4). Networks: nis_intro(7). Standards: standards(5). delim off getprotobynumber(3)