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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
       entry

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
       return a protocol entry.

       The entry may come from one of the  following  sources:	the  protocols
       file  (see  protocols(4)),  and	the  NIS maps ``protocols.byname'' and
       ``protocols.bynumber''. The sources and their lookup order  are	speci‐
       fied in the /etc/nsswitch.conf file (see nsswitch.conf(4) for details).
       Some name services such as NIS will return only one name	 for  a	 host,
       whereas others such as 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
       unsafe 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, but in general may not be well-defined.  The seman‐
       tics of enumeration are discussed in nsswitch.conf(4).

BUGS
       Only the Internet protocols are currently understood.

SunOS 5.11			  10 Dec 2009	       getprotobyname(3SOCKET)
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