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Standard C Library Functions                                getprotobyname(3C)

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

       #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);

       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(5)),  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(5) 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 mul‐
       tithreaded 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‐

       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;

       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

       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.

       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.



       See attributes(7) for descriptions of the following attributes:

       tab() box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) ATTRIBUTE  TYPEAT‐
       TRIBUTE VALUE _ MT-LevelSee NOTES below.

       netdb.h(3HEAD), nsswitch.conf(5), protocols(5), attributes(7)

       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.

       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 semantics
       of enumeration are discussed in nsswitch.conf(5).

       Only the Internet protocols are currently understood.

Oracle Solaris 11.4               19 May 2014               getprotobyname(3C)
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