Creating a temporary SMTP server to 'catch' domain validation emails

One problem that has come up a time or two is dealing with email-based domain validation (specifically in this case for the issuance of TLS certificates) on domains that aren’t actually configured to receive email. Yes, in a perfect world, it would be easier to switch to DNS-based validation (since we have to have control of the DNS for the domain, we need it later), but let’s just assume that’s not an option. So, how do we ‘catch’ the activation email so we can prove we can receive email on that domain?


Making Fish Shell Smile

When working in a shell, from time to time, I need to know if a command succeeded or failed. Sometimes, it’s easy:

$ make noise

make: *** No rule to make target `noise'.  Stop.

Sometimes, less so:

$ grep frog podcasts.json > podcasts-about-frogs.txt

Since, alas, I don’t have any podcasts about frogs, that command would fail silently. But that’s fixable!

$ grep frog podcasts.json > podcasts-about-frogs.txt

$ # Bash/Zsh
$ echo $?

$ # Fish
$ echo $status


SSH Config ProxyCommand Tricks

Working in security/operations in the tech industry, I use SSH a lot. To various different machines (some with hostnames, some without), using various different users and keys, and often (as was the case in my previous post) via a bastion host. Over the years, I’ve collected a number of SSH tricks that make my life easier.


Dynamic Automatic Proxies

On of the advantages of working in computer programming is that I can work from anywhere I have a computer and an internet connection. One of the disadvantages is that many of the resources that I need to do my job are locked to only be accessible within a specific network (albeit with a bastion host).

I long ago set up my SSH config to create an SSH tunnel and I can proxy many applications through that just by setting the HTTP_PROXY and/or HTTPS_PROXY environment variables. The downside of this though is that if I’m actually on a ‘safe’ network, there’s no reason to use the bastion host and I would actually be putting extra load on it.

My goal: write something that would let me automatically proxy applications when I need to but not when I don’t.


AoC 2017: Library Functions

As mentioned in the main post, I’m structuring my solutions a bit differently this year. Rather than repeating the same relatively lengthy header in each function, we’re going to have a few shared files that can be imported or used for every problem.


Command line unicode search

Similar to Monday’s post about command line emoji search, I often find myself wanting to look up Unicode characters. I have a custom search engine / bookmark set up in Chrome / Firefox (uni %s maps to That actually works great, but given how relatively much of my day I spend on the command line, I thought it would be interesting to do something there:

$ uni delta
⍋	apl functional symbol delta stile
⍙	apl functional symbol delta underbar
⍍	apl functional symbol quad delta
≜	delta equal to
Δ	greek capital letter delta
δ	greek small letter delta
ẟ	latin small letter delta
ƍ	latin small letter turned delta
𝚫	mathematical bold capital delta
𝜟	mathematical bold italic capital delta
𝜹	mathematical bold italic small delta
𝛅	mathematical bold small delta
𝛥	mathematical italic capital delta
𝛿	mathematical italic small delta
𝝙	mathematical sans-serif bold capital delta
𝞓	mathematical sans-serif bold italic capital delta
𝞭	mathematical sans-serif bold italic small delta
𝝳	mathematical sans-serif bold small delta
ᵟ	modifier letter small delta


Command line emoji search

Sometimes, I find myself wanting to communicate in emoji.


How about this:

$ emoji chicken

$ emoji "which came first, the 🐔 or the 🥚"
which came first, the 🐔 or the 🍳