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


#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);  


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:


The official name of the network.


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


The type of the network number; always AF_INET.


The network number in host byte order.


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.



networks database file


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.


POSIX.1-2001, POSIX.1-2008, 4.3BSD.


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


getnetent_r(3), getprotoent(3), getservent(3)

RFC 1101


This page is part of release 5.11 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−pages/.

  Copyright 1993 David Metcalfe (

Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a
permission notice identical to this one.

Since the Linux kernel and libraries are constantly changing, this
manual page may be incorrect or out-of-date.  The author(s) assume no
responsibility for errors or omissions, or for damages resulting from
the use of the information contained herein.  The author(s) may not
have taken the same level of care in the production of this manual,
which is licensed free of charge, as they might when working

Formatted or processed versions of this manual, if unaccompanied by
the source, must acknowledge the copyright and authors of this work.

References consulted:
    Linux libc source code
    Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
    386BSD man pages
Modified Sat Jul 24 21:48:06 1993 by Rik Faith (