How can I make sure the result of the following command:

nc eth0 &> capture.txt

would capture the data + errors transmitted via eth0?

  • 2
    you want tcpdump not nc, and it's -i eth0 – Creek Aug 15 '14 at 17:03
  • @Creek please post that as an answer. – derobert Aug 15 '14 at 17:04
  • nc will not serve the purpose at all? what if i can not install tcpdump, am i stuck then? – Sean Aug 15 '14 at 17:10
  • 1
    @Sean not necessarily, you can create an iptables LOG rule which will log high level packet info to syslog – Creek Aug 15 '14 at 17:27

you want tcpdump not nc, and the syntax would be

tcpdump -i eth0

netcat is only for basic TCP/IP testing. tcpdump utilizes the libpcap library which allows for lowlevel interactions with packets and the likes


You should use tcpdump with the -w switch.


Replace INTERFACE with the interface you want to listen and FILENAME with the location of the file to which you need to capture the output.

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