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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | FILES | ATTRIBUTES | STANDARDS | HISTORY | SEE ALSO | COLOPHON |
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getnetent(3) Library Functions Manual getnetent(3)
getnetent, getnetbyname, getnetbyaddr, setnetent, endnetent - get
network entry
Standard C library (libc, -lc)
#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:
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.
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.
/etc/networks
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(), │ 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.
POSIX.1-2008.
POSIX.1-2001, 4.3BSD.
Before glibc 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 the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.9.1.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2024-06-26. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
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)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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