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Hello! I’ve been thinking about the terminal a lot and yesterday I got curious about all these “control codes”, like Ctrl-A, Ctrl-C, Ctrl-W, etc. What’s the deal with all of them? a table of ASCII control characters Here’s a table of all 33 ASCII control characters, and what they do on my machine (on Mac OS), more or less. There are about a million caveats, but I’ll talk about what it means and al

Yesterday I was thinking about how long it took me to get a colorscheme in my terminal that I was mostly happy with (SO MANY YEARS), and it made me wonder what about terminal colours made it so hard. So I asked people on Mastodon what problems they’ve run into with colours in the terminal, and I got a ton of interesting responses! Let’s talk about some of the problems and a few possible ways to fi

I wrote about how much I love fish in this blog post from 2017 and, 7 years of using it every day later, I’ve found even more reasons to love it. So I thought I’d write a new post with both the old reasons I loved it and some reasons. This came up today because I was trying to figure out why my terminal doesn’t break anymore when I cat a binary to my terminal, the answer was “fish fixes the termin

The other day I asked what folks on Mastodon find confusing about working in the terminal, and one thing that stood out to me was “editing a command you already typed in”. This really resonated with me: even though entering some text and editing it is a very “basic” task, it took me maybe 15 years of using the terminal every single day to get used to using Ctrl+A to go to the beginning of the line

Hello! The other day I ran a Mastodon poll asking people how confident they were that they understood how HEAD works in Git. The results (out of 1700 votes) were a little surprising to me: 10% “100%” 36% “pretty confident” 39% “somewhat confident?” 15% “literally no idea” I was surprised that people were so unconfident about their understanding – I’d been thinking of HEAD as a pretty straightforwa

Hello! I always wish that command line tools came with data about how popular their various options are, like: “basically nobody uses this one” “80% of people use this, probably take a look” “this one has 6 possible values but people only really use these 2 in practice” So I asked about people’s favourite git config options on Mastodon: what are your favourite git config options to set? Right now

Hello! I posted a comic on Mastodon this week about what’s in the .git directory and someone requested a text version, so here it is. I added some extra notes too. First, here’s the image. It’s a ~15 word explanation of each part of your .git directory. You can git clone https://github.com/jvns/inside-git if you want to run all these examples yourself. Here’s a table of contents: HEAD: .git/head b

Hello! I’ve been working on writing a zine about git so I’ve been thinking about git branches a lot. I keep hearing from people that they find the way git branches work to be counterintuitive. It got me thinking: what might an “intuitive” notion of a branch be, and how is it different from how git actually works? So in this post I want to briefly talk about an intuitive mental model I think many p

Hello! I’m slowly working on explaining git. One of my biggest problems is that after almost 15 years of using git, I’ve become very used to git’s idiosyncracies and it’s easy for me to forget what’s confusing about it. So I asked people on Mastodon: what git jargon do you find confusing? thinking of writing a blog post that explains some of git’s weirder terminology: “detached HEAD state”, “fast-

I write a lot about technologies that I found hard to learn about. A while back my friend Sumana asked me an interesting question – why are these things so hard to learn about? Why do they seem so mysterious? For example, take DNS. We’ve been using DNS since the 80s (for more than 35 years!). It’s used in every website on the internet. And it’s pretty stable – in a lot of ways, it works the exact

A few years ago I gave a short talk (slides) about myths that discourage people from blogging. I was chatting with a friend about blogging the other day and it made me want to write up that talk as a blog post. here are the myths: myth: you need to be original myth: you need to be an expert myth: posts need to be 100% correct myth: writing boring posts is bad myth: you need to explain every concep

Hello! I’m excited to announce a project I’ve been working on for a long time: a free guide to implementing your own DNS resolver in a weekend. The whole thing is about 200 lines of Python, including implementing all of the binary DNS parsing from scratch. Here’s the link: This project is a fun way to learn: How to parse a binary network protocol like DNS How DNS works behind the scenes (what’s ac

I really like using (and making!) programming playgrounds, and I got thinking the other day about how I didn’t have a great list of playgrounds to refer to. So I asked on Mastodon for links to cool playgrounds. Here’s what I came up with. I’d love to know what I missed. Compilers: godbolt compiler explorer by Matt Godbolt Shaders: shadertoy by Inigo Quilez and Pol Jeremias Arduino / IoT: wokwi fro

Hello! I’ve been writing some Javascript this week, and as always when I start a new frontend project, I was faced with the question: should I use a build system? I want to talk about what’s appealing to me about build systems, why I (usually) still don’t use them, and why I find it frustrating that some frontend Javascript libraries require that you use a build system. I’m writing this because mo

Hello! I was trying to write about floating point yesterday, and I found myself wondering about this calculation, with 64-bit floats: >>> 0.1 + 0.2 0.30000000000000004 I realized that I didn’t understand exactly how it worked. I mean, I know floating point calculations are inexact, and I know that you can’t exactly represent 0.1 in binary, but: there’s a floating point number that’s closer to 0.3

Hello! I’ve been thinking about writing a zine about how things are represented on computers in bytes, so I was thinking about floating point. I’ve heard a million times about the dangers of floating point arithmetic, like: addition isn’t associative (x + (y + z) is different from (x + y) + z) if you add very big values to very small values, you can get inaccurate results (the small numbers get lo

Hello! On Monday, we released a new zine: The Pocket Guide to Debugging! It has 47 of my favourite strategies for solving your sneakiest bugs. You can get it for $12 here: https://wizardzines.com/zines/debugging-guide, or get an 12-pack of all my zines here. Here’s the cover: the table of contents Here’s the table of contents! A few people mentioned that they were printing it out, so I made a PDF

Hello! A while back I wrote a post about how to write a toy DNS resolver in Go. In that post I left out “how to generate and parse DNS queries” because I thought it was boring, but a few people pointed out that they did not know how to parse and generate DNS queries and they were interested in how to do it. This made me curious – how much work is it do the DNS parsing? It turns out we can do it in

Hello! Today I asked on twitter about newer command line tools, like ripgrep and fd and fzf and exa and bat. I got a bunch of replies with tools I hadn’t heard of, so I thought I’d make a list here. A lot of people also pointed at the modern-unix list. replacements for standard tools ripgrep, ag, ack (grep) exa, lsd (ls) mosh (ssh) bat (cat) delta (a pager for git) fd (find) drill, dog (dig) duf (

I was talking to a friend last summer about what resources might be helpful for folks learning to program. My friend said they thought some people might benefit from a list of small and fun programming projects – the kind of thing you can do in an evening or weekend. So let’s talk about that! I like to write small programs that have some marginal utility in my life. Kind of like this: ah! A minor

Hello! I wrote a comic last week called “life of a DNS query” that explains how DNS resolvers work. In this post, I want to explain how DNS resolvers work in a different way – with a short Go program that does the same thing described in the comic. The main function (resolve) is actually just 20 lines, including comments. I usually find it easier to understand things work when they come in the for

Hello! Yesterday I tweeted this: I feel like the term "DNS propagation" is misleading, like you're not actually waiting for DNS records to "propagate", you're waiting for cached records to expire — 🔎Julia Evans🔍 (@b0rk) December 5, 2021 and I want to talk about it a little more. This came up because I was showing a friend a demo of how DNS caching works last week, and he realized that what was h

Hello! I talked to a couple of friends recently who mentioned they wished they knew how to use dig to make DNS queries, so here’s a quick blog post about it. When I first started using dig I found it a bit intimidating – there are so many options! I’m going to leave out most of dig’s options in this post and just talk about the ones I actually use. Also I learned recently that you can set up a .di

Hello! Recently I’ve been thinking about why I explain things the way I do. The usual way I write is: Try to learn a topic Read a bunch of explanations that I find confusing Eventually understand the topic Write an explanation that makes sense to me, to help others So why do I find all these explanations so confusing? I decided to try and find out! I came up with a list of 13 patterns that make ex

Yesterday I asked on Twitter about what problems people are solving with strace and as usual everyone really delivered! I got 200 answers and then spent a bunch of time manually categorizing them into 9 categories of problems. All of the problems are about either finding files a program depends on, figuring out why a program is stuck or slow, or finding out why a program is failing. These generall

Hello! Over the last few days I made a little tool called dnspeep that lets you see what DNS queries your computer is making, and what responses it’s getting. It’s about 250 lines of Rust right now. I’ll talk about how you can try it, what it’s for, why I made it, and some problems I ran into while writing it. how to try it I built some binaries so you can quickly try it out. For Linux (x86): wget

While editing the capabilities page of the how containers work zine, I found myself trying to explain why strace doesn’t work in a Docker container. The problem here is – if I run strace in a Docker container on my laptop, this happens: $ docker run -it ubuntu:18.04 /bin/bash $ # ... install strace ... root@e27f594da870:/# strace ls strace: ptrace(PTRACE_TRACEME, ...): Operation not permitted stra