getprotobynumber

GETPROTOENT(3)             Linux Programmer's Manual            GETPROTOENT(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
       This page is part of release 5.04 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/.




GNU                               2017-09-15                    GETPROTOENT(3)