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GETPROTOBYNAME(3SOCKET)				       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)), 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
       return  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
       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 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.

				  Apr 5, 2004	       GETPROTOBYNAME(3SOCKET)
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