captop v1.17 (libpcap version 1.8.1)
usage: captop [OPTIONS] [BPF expression]
Pcap options:
  -B --buffer SIZE             Set the operating system capture buffer size.
  -c count                     Exit after receiving count packets.
  -s --snaplen VALUE           Specify the capture length of packets in bytes.
  -t --timeout NUM             Specify the timeout in msec.
  -O --no-optimize             Do not run the packet-matching code optimizer.
     --next                    Use pcap_next instead of pcap_loop.
Range Filters:
  -F --filter [RANGES]         Range filters: e.g. -F 1-100,1024,8000-8010
Generator:
  -R --rand-ip                 Randomize IPs addresses.
  -g --genlen  VALUE           Specify the length of injected packets.
Interface:
  -i --interface IFNAME        Listen on interface.
  -o --output IFNAME           Inject packets into interface.
Handler:
  -H --handler source.c        Dynamically load the pcap handler.
Thread:
     --thread INT              Launch multiple capture threads.
     --fanout GROUP STRING     Enable fanout!
File:
  -r --read  FILE              Read packets from file.
  -w --write FILE              Write packets to file.
Miscellaneous:
     --version                 Print the version strings and exit.
  -? --help                    Print this help.