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 er‐
       ror 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(), endprotoent() │ Thread safety │ MT-Unsafe race:protoent 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  dif‐
       ferent 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)

GNU                                                                            2021-03-22                                                                 GETPROTOENT(3)