ghostli123@ghostli123-HP-Pro-3380-MT:~/Yang/12.29/tcpdump-4.3.0$ tcpdump -r ../2012.udp.pcap port 53 -w pureDNS.pcap
reading from file ../2012.udp.pcap, link-type EN10MB (Ethernet)
tcpdump: pcap_loop: bogus savefile header
ghostli123@ghostli123-HP-Pro-3380-MT:~/Yang/12.29/tcpdump-4.3.0$ tcpdump -r pureDNS.pcap port 53 -w ../DNS.pcap
reading from file pureDNS.pcap, link-type EN10MB (Ethernet)
ghostli123@ghostli123-HP-Pro-3380-MT:~/Yang/12.29/tcpdump-4.3.0$ tcpdump -r ../DNS.pcap port 53 -tttt -n > ../DNS.txt