Hi, people

I'd need your help concerning searching inside .cap files.
I have to go through a big pile of packets captured with airodump-ng and need to evaluate certain values in there. I'd like to open it and go though it with grep or something like that ... however, since airodump-ng produces a .cap-file this method does obviously not work right away. My current method is now to open it with Wireshark and go through it by hand and write the values on paper ... however, this is a very time-consuming process and since I need to go through a big pile of packets it's not practical.

Maybe I can convert the .cap file into ASCII? Or maybe a program to search inside .cap files exists already? I have gotten the advice to try it with tcpdump (since tcpdump can output to console) and then grep ... but tcpdump tells me that "wifi0 has no IPv4 address asssigned" and shuts down instantly without capturing anything...
Does anybody know help for my issue?