.\" Copyright (c) 2012 YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
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-.TH IF_NAMEINDEX 3 2012-11-21 "GNU" "Linux Programmer's Manual"
+.TH IF_NAMEINDEX 3 2019-03-06 "GNU" "Linux Programmer's Manual"
.SH NAME
if_nameindex, if_freenameindex \- get network interface names and indexes
.SH SYNOPSIS
.nf
.B #include <net/if.h>
-.sp
+.PP
.BI "struct if_nameindex *if_nameindex(void);
.BI "void if_freenameindex(struct if_nameindex *" "ptr" );
.fi
.SH DESCRIPTION
The
.BR if_nameindex ()
-function returns an array of
+function returns an array of
.I if_nameindex
structures, each containing information
about one of the network interfaces on the local system.
The
.I if_nameindex
structure contains at least the following entries:
-.sp
+.PP
.in +4n
-.nf
- unsigned int if_index; /* Index of interface (1, 2, ...) */
- char *if_name; /* Null-terminated name ("eth0", etc.) */
-.fi
+.EX
+unsigned int if_index; /* Index of interface (1, 2, ...) */
+char *if_name; /* Null-terminated name ("eth0", etc.) */
+.EE
.in
.PP
The
.I if_index
field contains the interface index.
The
-.I ifa_name
+.I if_name
field points to the null-terminated interface name.
The end of the array is indicated by entry with
.I if_index
set to zero and
-.I ifa_name
+.I if_name
set to NULL.
.PP
The data structure returned by
On success,
.BR if_nameindex ()
returns pointer to the array;
-on error, a NULL pointer is returned, and
+on error, NULL is returned, and
.I errno
is set appropriately.
.SH ERRORS
if:
.TP
.B ENOBUFS
-Insufficient resources unavailable.
+Insufficient resources available.
.PP
.BR if_nameindex ()
may also fail for any of the errors specified for
The
.BR if_nameindex ()
function first appeared in glibc 2.1, but before glibc 2.3.4,
-the implementation only supported interfaces with IPv4 addresses.
-Support of interfaces that don't have IPv4 addresses is only available
+the implementation supported only interfaces with IPv4 addresses.
+Support of interfaces that don't have IPv4 addresses is available only
on kernels that support netlink.
-.SH EXAMPLE
+.SH ATTRIBUTES
+For an explanation of the terms used in this section, see
+.BR attributes (7).
+.TS
+allbox;
+lb lb lb
+l l l.
+Interface Attribute Value
+T{
+.BR if_nameindex (),
+.br
+.BR if_freenameindex ()
+T} Thread safety MT-Safe
+.TE
+.sp 1
+.SH CONFORMING TO
+POSIX.1-2001, POSIX.1-2008, RFC\ 3493.
+.PP
+This function first appeared in BSDi.
+.SH EXAMPLES
The program below demonstrates the use of the functions described
on this page.
An example of the output this program might produce is the following:
+.PP
.in +4n
-.nf
+.EX
$ \fB./a.out\fI
1: lo
2: wlan0
3: em1
-.fi
+.EE
.in
.SS Program source
-.nf
+.EX
#include <net/if.h>
#include <stdio.h>
#include <stdlib.h>
exit(EXIT_FAILURE);
}
- for (i = if_ni; ! (i\->if_index == 0 && i\->if_name == NULL); i++)
- printf("%u: %s\\n", i\->if_index, i\->if_name);
+ for (i = if_ni; ! (i\->if_index == 0 && i\->if_name == NULL); i++)
+ printf("%u: %s\en", i\->if_index, i\->if_name);
if_freenameindex(if_ni);
exit(EXIT_SUCCESS);
-}
-.fi
-.SH CONFORMING TO
-RFC\ 3493, POSIX.1-2001.
-
-This function first appeared in BSDi.
+}
+.EE
.SH SEE ALSO
.BR getsockopt (2),
.BR setsockopt (2),
.BR getifaddrs (3),
.BR if_indextoname (3),
-.BR if_nameindex (3),
.BR if_nametoindex (3),
.BR ifconfig (8)
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