A while back I tidied my dotfiles into a single repo, managed by chezmoi and added a few new functions which I decided are worth sharing. These functions are designed to make some information gathering tasks easier, so if you're the type of person who runs dig, whois or curl a lot, then read on.

Dotfiles

I've mentioned dotfiles a couple of times before, but in case you've not heard of them, dotfiles are configuration files, so called because they often start with a dot, which hides them from standard invocations of unix utilities like ls. [dotfiles] repos became popular not long after GitHub appeared on the scene, they're a great way to move your settings between machines and browsing other peoples’ files is a fun way of learning about software.

At first, everyone invented their own ways to manage their dotfiles. For example, I had a simple Rakefile which linked files from the checked out repo into my home directory. As you might expect though, in the last decade a lot has changed, and there are now loads of ways to manage your dotfiles. A few projects are listed here, but the one I've chosen to use (chezmoi isn't, so make sure you look around if you're on the market.

Using a proper full-fledged open-source project beats custom scripts by miles, there's more functionality and fewer bugs (probably!). chezmoi's cool features include secret storage and templating, so you can automatically update files on different systems. The files can still live in git, so you can easily keep them on github, or in keybase.

I won't go into any more detail here but if you work on multiple systems and aren't using a system like chezmoi already then do. It's worth the effort to set up!

Network functions: extracting URLs

I frequently have to run various networking utilities against IP addresses and DNS names, and modern browsers make it a faff to copy only the bit you need to perform your lookup on. For example, if I copy the contents of my browser's address bar right now, I get:

https://github.com/mattfoster/dotfiles/blob/master/dot_zsh/network.zsh

and if I decide I want to get the IP address from that, I can't just use the URL as an argument to dig:

$ dig https://github.com/mattfoster/dotfiles/blob/master/dot_zsh/network.zsh

; <<>> DiG 9.10.6 <<>> https://github.com/mattfoster/dotfiles/blob/master/dot_zsh/network.zsh
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 24396
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;https://github.com/mattfoster/dotfiles/blob/master/dot_zsh/network.zsh.	IN A

;; Query time: 28 msec
;; SERVER: 10.0.1.1#53(10.0.1.1)
;; WHEN: Sun Dec 29 17:38:41 GMT 2019
;; MSG SIZE  rcvd: 88

The same will happen with just about any other utility you can think of (host, nslookup, ping, whois).

So, to save a little time, I have a collection of shell functions which extract DNS names from URLs and pass them through to the utility I want to run.

% dig https://github.com/mattfoster/dotfiles/blob/master/dot_zsh/network.zsh

; <<>> DiG 9.10.6 <<>> github.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 58832
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;github.com.			IN	A

;; ANSWER SECTION:
github.com.		59	IN	A	140.82.118.3

;; Query time: 36 msec
;; SERVER: 10.0.1.1#53(10.0.1.1)
;; WHEN: Sun Dec 29 17:40:55 GMT 2019
;; MSG SIZE  rcvd: 44

This isn't particularly complex, but it saves a lot of time if you do this often. The file at network.zsh wraps:

• dig • nslookup • host • whois • ping

and I update it relatively frequently. The file should work in bash as well as zsh.

Network functions: other bits

In addition to the utilities above, I have a fews of other handy functions:

  • headers runs curl -I -X GET on a URL, this makes a GET request but then only displays the headers, not the body. This is better than making a HEAD request with just curl -I, as in my experience they often return different content.
  • ipwhois resolves a supplied DNS name or URL to an IP address (chopping out a protocol and any path parts if needed) and runs whois on the result. If the result is already an IP address it uses that. This currently only supports IPv4, but I'll update it soon.
  • pcurl sets proxy environment variables and runs curl. This is a fast way to get a URL into an intercepting proxy like Burp Suite.
  • ipsort sorts lists of IPv4 addresses.

As I said above, you can find this at network.zsh. I also plan to add some more IPv6 support in the near future.