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

NAME
       getnetent, getnetbyname, getnetbyaddr, setnetent, endnetent - get network 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 database and returns a netent structure containing the broken-out fields from the entry.  A con‐
       nection 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.

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

GNU                                                                            2021-03-22                                                                   GETNETENT(3)