getnetent(3) — Linux manual page


getnetent(3)            Library Functions Manual            getnetent(3)

NAME         top

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

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #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         top

       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

       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.

              A NULL-terminated list of alternative names for the

              The type of the network number; always AF_INET.

       n_net  The network number in host byte order.

RETURN VALUE         top

       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

FILES         top

              networks database file

ATTRIBUTES         top

       For an explanation of the terms used in this section, see
       │ 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.

STANDARDS         top


HISTORY         top

       POSIX.1-2001, 4.3BSD.

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

SEE ALSO         top

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

COLOPHON         top

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Linux man-pages 6.9.1          2024-05-02                   getnetent(3)

Pages that refer to this page: getent(1)getnetent_r(3)getprotoent(3)getservent(3)inet(3)networks(5)nsswitch.conf(5)