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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 connec-
       tion 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/.
GNU                               2017-09-15                    GETPROTOENT(3)