Tcpdump little book

    1. ......
    2.         /*
    3.          * We're doing a live capture.
    4.          */
    5.         if (device == NULL) {
    6.             /*
    7.              * No interface was specified.  Pick one.
    8.              */
    9. #ifdef HAVE_PCAP_FINDALLDEVS
    10.              * Find the list of interfaces, and pick
    11.              * the first interface.
    12.              */
    13.             if (pcap_findalldevs(&devlist, ebuf) == -1)
    14.                 error("%s", ebuf);
    15.             if (devlist == NULL)
    16.                 error("no interfaces available for capture");
    17.             device = strdup(devlist->name);
    18.             pcap_freealldevs(devlist);
    19.             /*
    21.              * chooses.
    22.              */
    23.             device = pcap_lookupdev(ebuf);
    24.             if (device == NULL)
    25.                 error("%s", ebuf);
    26. #endif
    27.         }