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| .TH IF_NAMEINDEX 3 2015-08-08 "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 |
| .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 |
| .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 |
| .in +4n |
| .nf |
| unsigned int if_index; /* Index of interface (1, 2, ...) */ |
| char *if_name; /* Null-terminated name ("eth0", etc.) */ |
| .fi |
| .in |
| .PP |
| The |
| .I if_index |
| field contains the interface index. |
| The |
| .I ifa_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 |
| set to NULL. |
| .PP |
| The data structure returned by |
| .BR if_nameindex () |
| is dynamically allocated and should be freed using |
| .BR if_freenameindex () |
| when no longer needed. |
| .SH RETURN VALUE |
| On success, |
| .BR if_nameindex () |
| returns pointer to the array; |
| on error, NULL is returned, and |
| .I errno |
| is set appropriately. |
| .SH ERRORS |
| .BR if_nameindex () |
| may fail and set |
| .I errno |
| if: |
| .TP |
| .B ENOBUFS |
| Insufficient resources available. |
| .PP |
| .BR if_nameindex () |
| may also fail for any of the errors specified for |
| .BR socket (2), |
| .BR bind (2), |
| .BR ioctl (2), |
| .BR getsockname (2), |
| .BR recvmsg (2), |
| .BR sendto (2), |
| or |
| .BR malloc (3). |
| .SH VERSIONS |
| The |
| .BR if_nameindex () |
| function first appeared in glibc 2.1, but before glibc 2.3.4, |
| 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 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 |
| |
| .SH CONFORMING TO |
| POSIX.1-2001, POSIX.1-2008, RFC\ 3493. |
| |
| This function first appeared in BSDi. |
| .SH EXAMPLE |
| 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: |
| |
| .in +4n |
| .nf |
| $ \fB./a.out\fI |
| 1: lo |
| 2: wlan0 |
| 3: em1 |
| .fi |
| .in |
| .SS Program source |
| .nf |
| #include <net/if.h> |
| #include <stdio.h> |
| #include <stdlib.h> |
| #include <unistd.h> |
| |
| int |
| main(int argc, char *argv[]) |
| { |
| struct if_nameindex *if_ni, *i; |
| |
| if_ni = if_nameindex(); |
| if (if_ni == NULL) { |
| perror("if_nameindex"); |
| 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); |
| |
| if_freenameindex(if_ni); |
| |
| exit(EXIT_SUCCESS); |
| } |
| .fi |
| .SH SEE ALSO |
| .BR getsockopt (2), |
| .BR setsockopt (2), |
| .BR getifaddrs (3), |
| .BR if_indextoname (3), |
| .BR if_nametoindex (3), |
| .BR ifconfig (8) |