pcap_lookupdev.3pcap - Man Page
find the default device on which to capture
#include <pcap/pcap.h> char errbuf[PCAP_ERRBUF_SIZE]; [DEPRECATED] char *pcap_lookupdev(char *errbuf);
This interface is obsoleted by pcap_findalldevs(3PCAP). To find a default device on which to capture, call pcap_findalldevs() and, if the list it returns is not empty, use the first device in the list. (If the list is empty, there are no devices on which capture is possible.)
If pcap_init(3PCAP) has been called, this interface always returns NULL.
pcap_lookupdev() returns a pointer to a string giving the name of a network device suitable for use with pcap_create(3PCAP) and pcap_activate(3PCAP), or with pcap_open_live(3PCAP), and with pcap_lookupnet(3PCAP). If there is an error, or if pcap_init(3PCAP) has been called, NULL is returned and errbuf is filled in with an appropriate error message. errbuf is assumed to be able to hold at least PCAP_ERRBUF_SIZE chars.
The pointer returned by pcap_lookupdev() points to a static buffer; subsequent calls to pcap_lookupdev() in the same thread, or calls to pcap_lookupdev() in another thread, may overwrite that buffer.
In WinPcap and Npcap, this function may return a UTF-16 string rather than an ASCII or UTF-8 string.