getnetbyaddr(3)



GETNETENT(3)               Linux Programmer's Manual              GETNETENT(3)

NAME
       getnetent,  getnetbyname, getnetbyaddr, setnetent, endnetent - get net-
       work entry

SYNOPSIS
       #include <netdb.h>

       struct netent *getnetent(void);

       struct netent *getnetbyname(const char *name);

       struct netent *getnetbyaddr(uint32_t net, int type);

       void setnetent(int stayopen);

       void endnetent(void);

DESCRIPTION
       The getnetent() function reads the next entry from the  networks  data-
       base  and  returns  a netent structure containing the broken-out fields
       from the entry.  A connection is opened to the database if necessary.

       The getnetbyname() function returns a netent structure  for  the  entry
       from the database that matches the network name.

       The  getnetbyaddr()  function  returns a netent structure for the entry
       from the database that matches the network number  net  of  type  type.
       The net argument must be in host byte order.

       The  setnetent()  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 getnet*() functions.

       The endnetent() function closes the connection to the database.

       The netent structure is defined in <netdb.h> as follows:

           struct netent {
               char      *n_name;     /* official network name */
               char     **n_aliases;  /* alias list */
               int        n_addrtype; /* net address type */
               uint32_t   n_net;      /* network number */
           }

       The members of the netent structure are:

       n_name The official name of the network.

       n_aliases
              A NULL-terminated list of alternative names for the network.

       n_addrtype
              The type of the network number; always AF_INET.

       n_net  The network number in host byte order.

RETURN VALUE
       The getnetent(), getnetbyname() and getnetbyaddr() functions  return  a
       pointer  to  a statically allocated netent structure, or a null pointer
       if an error occurs or the end of the file is reached.

FILES
       /etc/networks
              networks database file

ATTRIBUTES
       For  an  explanation  of  the  terms  used   in   this   section,   see
       attributes(7).

       +---------------+---------------+---------------------------+
       |Interface      | Attribute     | Value                     |
       +---------------+---------------+---------------------------+
       |getnetent()    | Thread safety | MT-Unsafe race:netent     |
       |               |               | race:netentbuf env locale |
       +---------------+---------------+---------------------------+
       |getnetbyname() | Thread safety | MT-Unsafe race:netbyname  |
       |               |               | env locale                |
       +---------------+---------------+---------------------------+
       |getnetbyaddr() | Thread safety | MT-Unsafe race:netbyaddr  |
       |               |               | locale                    |
       +---------------+---------------+---------------------------+
       |setnetent(),   | Thread safety | MT-Unsafe race:netent env |
       |endnetent()    |               | locale                    |
       +---------------+---------------+---------------------------+
       In  the above table, netent in race:netent signifies that if any of the
       functions setnetent(), getnetent(), or endnetent() 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.

NOTES
       In glibc versions before 2.2, the net argument of getnetbyaddr() was of
       type long.

SEE ALSO
       getnetent_r(3), getprotoent(3), getservent(3)
       RFC 1101

COLOPHON
       This page is part of release 4.16 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                      GETNETENT(3)

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