getprotoent(3)                                        Library Functions Manual                                       getprotoent(3)

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

LIBRARY
       Standard C library (libc, -lc)

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 struc‐
       ture 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 num‐
       ber 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(), 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  end‐
       protoent() are used in parallel in different threads of a program, then data races could occur.

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

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

Linux man-pages 6.03                                         2022-12-15                                              getprotoent(3)