pwru VS jq

if you have a recent enough kernel, this change https://github.com/cilium/pwru/pull/148 means that it will print the reason the packet was dropped in the output - see https://lwn.net/Articles/885729/

There's a whole heap of reasons a packet can be dropped:

[pwru](https://github.com/cilium/pwru) is a fun new tool from the Cilium folks for tracing network packets in the kernel. Like tcpdump but it shows you the full path including kernel syscalls. Lets you debug much deeper than "when the packet gets to this port it gets dropped".

I recently came across another useful utility for debugging unexpected packet drops - PWRU[0] (Packet, Where Are You) by Cilium.

It uses eBPF to try to trace the path of the packet through the kernel. Haven't needed to use it yet, but it could have saved me a lot of trouble in the past.

[0]: https://github.com/cilium/pwru

That should recursively list directories, counting only the files within each, and output² jsonl that can be further mangled within the shell². You could just as easily populate an associative array for further work, or $whatever. Unlike bash, zsh has reasonable behaviour around quoting and whitespace too.

¹ https://zsh.sourceforge.io/Doc/Release/User-Contributions.ht...

² https://github.com/jpmens/jo

³ https://github.com/stedolan/jq

What I miss from jq and what is implemented but unreleased is platform independent line delimiters.

jq on Windows produces \r\n terminated lines which can be annoying when used with Cygwin / MSYS2 / WSL. The '--binary' option to not convert line delimiters is one of those pending improvements.

https://github.com/stedolan/jq/commit/0dab2b18d73e561f511801...

If you have jq installed you can use it to make the output look nicer.

It requires jq for JSON processing and GNU parallel for concurrent searches in the notebooks.

jq is your friend.

The jq command (https://stedolan.github.io/jq/) is useful pulling that information out.