getprotobynumber(3)

NAME

   getprotoent, getprotobyname, getprotobynumber, setprotoent, endprotoent
   - get protocol entry

SYNOPSIS

   #include <netdb.h>

   struct protoent *getprotoent(void);

   struct protoent *getprotobyname(const char *name);

   struct protoent *getprotobynumber(int proto);

   void setprotoent(int stayopen);

   void endprotoent(void);

DESCRIPTION

   The getprotoent() function reads the  next  entry  from  the  protocols
   database (see protocols(5)) and returns a protoent structure containing
   the broken-out fields from the entry.  A connection is  opened  to  the
   database if necessary.

   The  getprotobyname()  function  returns  a  protoent structure for the
   entry from the  database  that  matches  the  protocol  name  name.   A
   connection is opened to the database if necessary.

   The  getprotobynumber()  function  returns a protoent structure for the
   entry from the database that matches the  protocol  number  number.   A
   connection is opened to the database if necessary.

   The setprotoent() function opens a connection to the database, and sets
   the next entry to the first entry.  If stayopen is  nonzero,  then  the
   connection  to  the database will not be closed between calls to one of
   the getproto*() functions.

   The endprotoent() function closes the connection to the database.

   The protoent structure is defined in <netdb.h> as follows:

       struct protoent {
           char  *p_name;       /* official protocol name */
           char **p_aliases;    /* alias list */
           int    p_proto;      /* protocol number */
       }

   The members of the protoent structure are:

   p_name The official name of the protocol.

   p_aliases
          A NULL-terminated list of alternative names for the protocol.

   p_proto
          The protocol number.

RETURN VALUE

   The getprotoent(), getprotobyname()  and  getprotobynumber()  functions
   return  a  pointer  to  a statically allocated protoent structure, or a
   null pointer if an error occurs or the end of the file is reached.

FILES

   /etc/protocols
          protocol database file

ATTRIBUTES

   For  an  explanation  of  the  terms  used   in   this   section,   see
   attributes(7).

   ┌───────────────────┬───────────────┬──────────────────────────────┐
   │Interface          │ Attribute     │ Value                        │
   ├───────────────────┼───────────────┼──────────────────────────────┤
   │getprotoent()      │ Thread safety │ MT-Unsafe race:protoent      │
   │                   │               │ race:protoentbuf locale      │
   ├───────────────────┼───────────────┼──────────────────────────────┤
   │getprotobyname()   │ Thread safety │ MT-Unsafe race:protobyname   │
   │                   │               │ locale                       │
   ├───────────────────┼───────────────┼──────────────────────────────┤
   │getprotobynumber() │ Thread safety │ MT-Unsafe race:protobynumber │
   │                   │               │ locale                       │
   ├───────────────────┼───────────────┼──────────────────────────────┤
   │setprotoent(),     │ Thread safety │ MT-Unsafe race:protoent      │
   │endprotoent()      │               │ locale                       │
   └───────────────────┴───────────────┴──────────────────────────────┘
   In  the above table, protoent in race:protoent signifies that if any of
   the functions setprotoent(), getprotoent(), or endprotoent()  are  used
   in  parallel  in  different threads of a program, then data races could
   occur.

CONFORMING TO

   POSIX.1-2001, POSIX.1-2008, 4.3BSD.

SEE ALSO

   getnetent(3), getprotoent_r(3), getservent(3), protocols(5)

COLOPHON

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   description  of  the project, information about reporting bugs, and the
   latest    version    of    this    page,    can     be     found     at
   https://www.kernel.org/doc/man-pages/.

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