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

       This  page  is  part of release 4.15 of the Linux man-pages project.  A 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/.