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getprotobyname(3SOCKET)	   Sockets Library Functions   getprotobyname(3SOCKET)

NAME
       getprotobyname, getprotobyname_r, getprotobynumber, getprotobynumber_r,
       getprotoent, getprotoent_r, setprotoent,	endprotoent - get protocol en-
       try

SYNOPSIS
       cc [ flag ... ] file ...	-lsocket -lnsl [ library ... ]
       #include	<netdb.h>

       struct protoent *getprotobyname(const char *name);

       struct  protoent	 *getprotobyname_r(const  char	*name, struct protoent
       *result,	char *buffer, int buflen);

       struct protoent *getprotobynumber(int proto);

       struct protoent *getprotobynumber_r(int proto, struct protoent *result,
       char *buffer, int buflen);

       struct protoent *getprotoent(void);

       struct  protoent	 *getprotoent_r(struct protoent	*result, char *buffer,
       int buflen);

       int setprotoent(int stayopen);

       int endprotoent(void);

DESCRIPTION
       These functions return a	protocol entry.	Two types  of  interfaces  are
       supported:  reentrant  (getprotobyname_r(),  getprotobynumber_r(),  and
       getprotoent_r())	and  non-reentrant  (getprotobyname(),	getprotobynum-
       ber(),  and getprotoent()). The reentrant functions can be used in sin-
       gle-threaded applications and are safe for multithreaded	 applications,
       making them the preferred interfaces.

       The  reentrant routines require additional parameters which are used to
       return results data. result is a	pointer	to a struct protoent structure
       and  will  be where the returned	results	will be	stored.	buffer is used
       as storage space	for elements of	the returned results.  buflen  is  the
       size of buffer and should be large enough to contain all	returned data.
       buflen must be at least 1024 bytes.

       getprotobyname_r(), getprotobynumber_r(), and getprotoent_r() each  re-
       turn a protocol entry.

       The  entry  may	come  from one of the following	sources: the protocols
       file (see protocols(4)),	the NIS	maps ``protocols.byname'' and ``proto-
       cols.bynumber'',	 and  the  NIS+	 table	``protocols''. The sources and
       their lookup order are specified	in the	/etc/nsswitch.conf  file  (see
       nsswitch.conf(4)	 for details). Some name services such as NIS will re-
       turn only one name for a	host, whereas others such as NIS+ or DNS  will
       return all aliases.

       The  getprotobyname_r() and getprotobynumber_r()	functions sequentially
       search from the beginning of the	file until a matching protocol name or
       protocol	number is found, or until an EOF is encountered.

       getprotobyname()	 and getprotobynumber()	have the same functionality as
       getprotobyname_r() and getprotobynumber_r() except that a static	buffer
       is  used	 to  store  returned results.  These functions are Unsafe in a
       multithreaded application.

       getprotoent_r() enumerates protocol entries: successive calls  to  get-
       protoent_r()  will  return  either successive protocol entries or NULL.
       Enumeration might not be	supported by some sources. If multiple threads
       call getprotoent_r(), each will retrieve	a subset of the	protocol data-
       base.

       getprotent() has	the same functionality as getprotent_r() except	that a
       static  buffer  is used to store	returned results.  This	routine	is un-
       safe in a multithreaded application.

       setprotoent() "rewinds" to the beginning	of the enumeration of protocol
       entries.	 If the	stayopen flag is non-zero, resources such as open file
       descriptors are not deallocated after each call to getprotobynumber_r()
       and  getprotobyname_r().	 Calls to getprotobyname_r() , The getprotoby-
       name(), getprotobynumber_r(), and  getprotobynumber()  functions	 might
       leave  the  enumeration	in  an	indeterminate  state, so setprotoent()
       should be called	before the first call to  getprotoent_r()  or  getpro-
       toent().	  The  setprotoent()  function	has  process-wide  scope,  and
       ``rewinds'' the	protocol  entries  for	all  threads  calling  getpro-
       toent_r() as well as main-thread	calls to getprotoent().

       The endprotoent() function can be called	to indicate that protocol pro-
       cessing is complete; the	system may then	close any open protocols file,
       deallocate  storage, and	so forth.  It is legitimate, but possibly less
       efficient, to call more protocol	functions after	endprotoent().

       The internal representation of a	protocol entry is a protoent structure
       defined in <netdb.h> with the following members:

       char  *p_name;
       char  **p_aliases;
       int   p_proto;

RETURN VALUES
       The  getprotobyname_r(),	 getprotobyname(),  getprotobynumber_r(),  and
       getprotobynumber() functions return a pointer to	a struct  protoent  if
       they  successfully  locate  the	requested entry; otherwise they	return
       NULL.

       The getprotoent_r() and getprotoent() functions return a	pointer	 to  a
       struct protoent if they successfully enumerate an entry;	otherwise they
       return NULL, indicating the end of the enumeration.

ERRORS
       The getprotobyname_r(), getprotobynumber_r(), and getprotoent_r() func-
       tions will fail if:

       ERANGE	       The  length of the buffer supplied by the caller	is not
		       large enough to store the result.

FILES
       /etc/protocols

       /etc/nsswitch.conf

ATTRIBUTES
       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE	TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |See NOTES	below.		   |
       +-----------------------------+-----------------------------+

SEE ALSO
       intro(3), nsswitch.conf(4), protocols(4), attributes(5),	netdb.h(3HEAD)

NOTES
       Although	getprotobyname_r(), getprotobynumber_r(), and  getprotoent_r()
       are not mentioned by POSIX 1003.1:2001, they were added to complete the
       functionality provided by similar thread-safe functions.

       When compiling multithreaded applications, see  intro(3), Notes On Mul-
       tithread	 Applications, for information about the use of	the _REENTRANT
       flag.

       The getprotobyname_r(), getprotobynumber_r(), and getprotoent_r() func-
       tions  are reentrant and	multithread safe. The reentrant	interfaces can
       be used in single-threaded as well as  multithreaded  applications  and
       are therefore the preferred interfaces.

       The getprotobyname(), getprotobyaddr(), and getprotoent() functions use
       static storage, so returned data	must be	copied if it is	to  be	saved.
       Because	of  their use of static	storage	for returned data, these func-
       tions are not safe for multithreaded applications.

       The setprotoent() and endprotoent() functions have process-wide	scope,
       and are therefore not safe in multi-threaded applications.

       Use of getprotoent_r() and getprotoent()	is discouraged;	enumeration is
       well-defined for	the protocols file and is  supported  (albeit  ineffi-
       ciently)	for NIS	and NIS+, but in general may not be well-defined.  The
       semantics of enumeration	are discussed in nsswitch.conf(4).

BUGS
       Only the	Internet protocols are currently understood.

SunOS 5.10			  5 Apr	2004	       getprotobyname(3SOCKET)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | FILES | ATTRIBUTES | SEE ALSO | NOTES | BUGS

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