GETNETENT(3)           FreeBSD Library Functions Manual           GETNETENT(3)

NAME

     getnetent, getnetbyaddr, getnetbyname, 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);

     int
     getnetent_r(struct netent *ne, char *buffer, size_t buflen,
         struct netent **result, int *h_errnop);

     int
     getnetbyaddr_r(uint32_t net, int type, struct netent *ne, char *buffer,
         size_t buflen, struct netent **result, int, *h_errorp");

     int
     getnetbyname_r(const char *name, struct netent *ne, char *buffer,
         size_t buflen, struct netent **result, int *h_errorp);

DESCRIPTION

     The getnetent(), getnetbyname(), and getnetbyaddr() functions each return
     a pointer to an object with the following structure describing an
     internet network.  This structure contains either the information
     obtained from the nameserver, broken-out fields of a line in the network
     data base /etc/networks, or entries supplied by the yp(8) system.  The
     order of the lookups is controlled by the `networks' entry in
     nsswitch.conf(5).

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

     The members of this structure are:

     n_name      The official name of the network.

     n_aliases   A zero terminated list of alternate names for the network.

     n_addrtype  The type of the network number returned; currently only
                 AF_INET.

     n_net       The network number.  Network numbers are returned in machine
                 byte order.

     The getnetent() function reads the next line of the file, opening the
     file if necessary.

     The setnetent() function opens and rewinds the file.  If the stayopen
     flag is non-zero, the net data base will not be closed after each call to
     getnetbyname() or getnetbyaddr().

     The endnetent() function closes the file.

     The getnetbyname() function and getnetbyaddr() sequentially search from
     the beginning of the file until a matching net name or net address and
     type is found, or until EOF is encountered.  The type argument must be
     AF_INET.  Network numbers are supplied in host order.

     Functions with the _r suffix provide reentrant versions of their
     respective counterparts.  The caller must supply five additional
     parameters: a struct netent variable to be filled on success, a buffer of
     buflen bytes in size, a struct netent result variable that will point to
     the result on success or be set to NULL on failure or if the name is not
     found.  The h_errnop variable will be filled with the error code if any.
     All these functions return 0 on success.

FILES

     /etc/networks
     /etc/nsswitch.conf
     /etc/resolv.conf

DIAGNOSTICS

     Null pointer returned on EOF or error.

SEE ALSO

     networks(5)

     RFC 1101

HISTORY

     The getnetent(), getnetbyaddr(), getnetbyname(), setnetent(), and
     endnetent() functions appeared in 4.2BSD.

BUGS

     The data space used by these functions is thread-specific; if future use
     requires the data, it should be copied before any subsequent calls to
     these functions overwrite it.  Only Internet network numbers are
     currently understood.  Expecting network numbers to fit in no more than
     32 bits is probably naive.

FreeBSD 15.1-STABLE-HBSD         June 27, 2022                    GETNETENT(3)