if_nametoindex - Online Linux Manual PageSection : 3
Updated : 2022-12-15
Source : Linux man-pages 6.03

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NAMEif_nametoindex, if_indextoname − mappings between network interface names and indexes

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LIBRARYStandard C library (libc, −lc)

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SYNOPSIS#include <net/if.h>unsigned int if_nametoindex(const char *ifname); char *if_indextoname(unsigned int ifindex, char *ifname);

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DESCRIPTIONThe if_nametoindex() function returns the index of the network interface corresponding to the name ifname. The if_indextoname() function returns the name of the network interface corresponding to the interface index ifindex. The name is placed in the buffer pointed to by ifname. The buffer must allow for the storage of at least IF_NAMESIZE bytes.

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RETURN VALUEOn success, if_nametoindex() returns the index number of the network interface; on error, 0 is returned and errno is set to indicate the error. On success, if_indextoname() returns ifname; on error, NULL is returned and errno is set to indicate the error.

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ERRORSif_nametoindex() may fail and set errno if: ENODEV  No interface found with given name. if_indextoname() may fail and set errno if: ENXIO  No interface found for the index. if_nametoindex() and if_indextoname() may also fail for any of the errors specified for socket(2) or ioctl(2).

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ATTRIBUTESFor an explanation of the terms used in this section, see attributes(7). InterfaceAttributeValue if_nametoindex(), if_indextoname() Thread safetyMT-Safe

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STANDARDSPOSIX.1-2001, POSIX.1-2008, RFC 3493. This function first appeared in BSDi.

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SEE ALSOgetifaddrs(3), if_nameindex(3), ifconfig(8) 0

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