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NAME |LIBRARY |SYNOPSIS |DESCRIPTION |RETURN VALUE |ERRORS |ATTRIBUTES |STANDARDS |HISTORY |EXAMPLES |SEE ALSO |COLOPHON | |
if_nameindex(3) Library Functions Manualif_nameindex(3)if_nameindex, if_freenameindex - get network interface names and indexes
Standard C library (libc,-lc)
#include <net/if.h>struct if_nameindex *if_nameindex(void);void if_freenameindex(struct if_nameindex *ptr);
Theif_nameindex() function returns an array ofif_nameindex structures, each containing information about one of the network interfaces on the local system. Theif_nameindex structure contains at least the following entries: unsigned int if_index; /* Index of interface (1, 2, ...) */ char *if_name; /* Null-terminated name ("eth0", etc.) */ Theif_index field contains the interface index. Theif_name field points to the null-terminated interface name. The end of the array is indicated by entry withif_index set to zero andif_name set to NULL. The data structure returned byif_nameindex() is dynamically allocated and should be freed usingif_freenameindex() when no longer needed.On success,if_nameindex() returns pointer to the array; on error, NULL is returned, anderrno is set to indicate the error.
if_nameindex() may fail and seterrno if:ENOBUFS Insufficient resources available.if_nameindex() may also fail for any of the errors specified forsocket(2),bind(2),ioctl(2),getsockname(2),recvmsg(2),sendto(2), ormalloc(3).
For an explanation of the terms used in this section, seeattributes(7). ┌──────────────────────────────────────┬───────────────┬─────────┐ │Interface│Attribute│Value│ ├──────────────────────────────────────┼───────────────┼─────────┤ │if_nameindex(),if_freenameindex() │ Thread safety │ MT-Safe │ └──────────────────────────────────────┴───────────────┴─────────┘
POSIX.1-2008, RFC 3493.
glibc 2.1. POSIX.1-2001. BSDi. 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.
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: $./a.out; 1: lo 2: wlan0 3: em1Program source #include <net/if.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> int main(void) { 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); }getsockopt(2),setsockopt(2),getifaddrs(3),if_indextoname(3),if_nametoindex(3),ifconfig(8)
This page is part of theman-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-6.15.tar.gz fetched from ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on 2025-08-11. 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 isnot part of the original manual page), send a mail to man-pages@man7.orgLinux man-pages 6.15 2025-05-17if_nameindex(3)Pages that refer to this page:if_nametoindex(3)
HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH. | |