if_nametoindex(3)

1if_nametoindex(3)          Library Functions Manual          if_nametoindex(3)
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NAME

6       if_nametoindex,  if_indextoname  -  mappings  between network interface
7       names and indexes
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LIBRARY

10       Standard C library (libc, -lc)
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SYNOPSIS

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

19       The if_nametoindex() function returns the index of the  network  inter‐
20       face corresponding to the name ifname.
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22       The if_indextoname() function returns the name of the network interface
23       corresponding to the interface index ifindex.  The name  is  placed  in
24       the buffer pointed to by ifname.  The buffer must allow for the storage
25       of at least IF_NAMESIZE bytes.
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RETURN VALUE

28       On success, if_nametoindex() returns the index number  of  the  network
29       interface; on error, 0 is returned and errno is set to indicate the er‐
30       ror.
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32       On success, if_indextoname() returns ifname; on error, NULL is returned
33       and errno is set to indicate the error.
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ERRORS

36       if_nametoindex() may fail and set errno if:
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38       ENODEV No interface found with given name.
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40       if_indextoname() may fail and set errno if:
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42       ENXIO  No interface found for the index.
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44       if_nametoindex()  and if_indextoname() may also fail for any of the er‐
45       rors specified for socket(2) or ioctl(2).
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ATTRIBUTES

48       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
49       tributes(7).
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51       ┌────────────────────────────────────────────┬───────────────┬─────────┐
52       │Interface                                   │ Attribute     │ Value   │
53       ├────────────────────────────────────────────┼───────────────┼─────────┤
54       │if_nametoindex(), if_indextoname()          │ Thread safety │ MT-Safe │
55       └────────────────────────────────────────────┴───────────────┴─────────┘
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STANDARDS

58       POSIX.1-2008, RFC 3493.
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HISTORY

61       POSIX.1-2001.  BSDi.
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