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  20 .TH PCAP_LOOKUPDEV 3PCAP "30 November 2023"
  21 .SH NAME
  22 pcap_lookupdev \- find the default device on which to capture
  23 .SH SYNOPSIS
  24 .nf
  25 .ft B
  26 #include <pcap/pcap.h>
  27 .ft
  28 .LP
  29 .nf
  30 .ft B
  31 char errbuf[PCAP_ERRBUF_SIZE];
  32 .ft
  33 .LP
  34 .ft B
  35 [DEPRECATED] char *pcap_lookupdev(char *errbuf);
  36 .ft
  37 .fi
  38 .SH DESCRIPTION
  39 .B This interface is obsoleted by
  40 .BR pcap_findalldevs (3PCAP).
  41 To find a default device on which to capture, call
  42 .BR pcap_findalldevs ()
  43 and, if the list it returns is not empty, use the first device in the
  44 list.  (If the list is empty, there are no devices on which capture is
  45 possible.)
  46 .I errbuf
  47 is a buffer large enough to hold at least
  48 .B PCAP_ERRBUF_SIZE
  49 chars.
  50 .LP
  51 .B If
  52 .BR pcap_init (3PCAP)
  53 .B has been called, this interface always returns
  54 .BR NULL .
  55 .LP
  56 .BR pcap_lookupdev ()
  57 returns a pointer to a string giving the name of a network device
  58 suitable for use with
  59 .BR pcap_create (3PCAP)
  60 and
  61 .BR \%pcap_activate (3PCAP),
  62 or with
  63 .BR pcap_open_live (3PCAP),
  64 and with
  65 .BR pcap_lookupnet (3PCAP).
  66 If there is an error,
  67 or if
  68 .BR pcap_init (3PCAP)
  69 has been called,
  70 .B NULL
  71 is returned and
  72 .I errbuf
  73 is filled in with an appropriate error message.
  74 .SH SEE ALSO
  75 .BR pcap (3PCAP)
  76 .SH BUGS
  77 The pointer returned by
  78 .BR pcap_lookupdev ()
  79 points to a static buffer; subsequent calls to
  80 .BR pcap_lookupdev ()
  81 in the same thread, or calls to
  82 .BR pcap_lookupdev ()
  83 in another thread, may overwrite that buffer.
  84 .LP
  85 In WinPcap and Npcap, this function may return a UTF-16 string rather
  86 than an ASCII or UTF-8 string.