NAME

       getnetent, getnetbyname, getnetbyaddr, setnetent, endnetent - get network entry

LIBRARY

       Standard C library (libc, -lc)

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 database 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(), endnetent() │ Thread safety │ MT-Unsafe race:netent env 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.

STANDARDS

       POSIX.1-2008.

HISTORY

       POSIX.1-2001, 4.3BSD.

       Before glibc 2.2, the net argument of getnetbyaddr() was of type long.

SEE ALSO

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