Here they are:

• the dig man page (now with examples)
• the tcpdump man page examples (this one is an update to the previous examples)

the goal: include the most basic examples

The goal here was really just to give the absolute most basic examples of how to use the tool, for people who use tcpdump or dig infrequently (or have never used it before!) and don’t remember how it works.

So far saying “hey, I want to write an examples section for beginners and infrequent users of this tools” has been working really well. It’s easy to explain, I think it makes sense from everything I’ve heard from users about what they want from a man page, and maintainers seem to find it compelling.

Thanks to Denis Ovsienko, Guy Harris, Ondřej Surý, and everyone else who reviewed the docs changes, it was a good experience and left me motivated to do a little more work on man pages.

why improve the man pages?

I’m interested in working on tools’ official documentation right now because:

• Man pages can actually have close to 100% accurate information! Going through a review process to make sure that the information is actually true has a lot of value.
• Even with basic questions “what are the most commonly used tcpdump flags”, often maintainers are aware of useful features that I’m not! For example I learned by working on these tcpdump examples that if you’re saving packets to a file with tcpdump -w out.pcap, it’s useful to pass -v to print a live summary of how many packets have been captured so far. That’s really useful, I didn’t know it, and I don’t think I ever would have noticed it on my own.

It’s kind of a weird place for me to be because honestly I always kind of assume documentation is going to be hard to read, and I usually just skip it and read a blog post or Stack Overflow comment or ask a friend instead. But right now I’m feeling optimistic, like maybe the documentation doesn’t have to be bad? Maybe it could be just as good as reading a really great blog post, but with the benefit of also being actually correct? I’ve been using the Django documentation recently, and it’s really good! We’ll see.

on avoiding writing the man page language

The tcpdump project tool’s man page is written in the roff language, which is kind of hard to use and that I really did not feel like learning it.

I handled this by writing a very basic markdown-to-roff script to convert Markdown to roff, using similar conventions to what the man page was already using. I could maybe have just used pandoc, but the output pandoc produced seemed pretty different, so I thought it might be better to write my own script instead. Who knows.

I did think it was cool to be able to just use an existing Markdown library’s ability to parse the Markdown AST and then implement my own code-emitting methods to format things in a way that seemed to make sense in this context.

man pages are complicated

I went on a whole rabbit hole learning about the history of roff, how it’s evolved since the 70s, and who’s working on it today, inspired by learning about the mandoc project that BSD systems (and some Linux systems, and I think Mac OS) use for formatting man pages. I won’t say more about that today though, maybe another time.

In general it seems like there’s a technical and cultural divide in how documentation works on BSD and on Linux that I still haven’t really understood, but I have been feeling curious about what’s going on in the BSD world.

The comments section is here.

I’ve spent a lot of time writing cheat sheets for tools (tcpdump, git, dig, etc) which have a man page as their primary documentation. This is because I often find the man pages hard to navigate to get the information I want.

Lately I’ve wondering – could the man page itself have an amazing cheat sheet in it? What might make a man page easier to use? I’m still very early in thinking about this but I wanted to write down some quick notes.

I asked some people on Mastodon for their favourite man pages, and here are some examples of interesting things I saw on those man pages.

an OPTIONS SUMMARY

If you’ve read a lot of man pages you’ve probably seen something like this in the SYNOPSIS: once you’re listing almost the entire alphabet, it’s hard

ls [-@ABCFGHILOPRSTUWabcdefghiklmnopqrstuvwxy1%,]

grep [-abcdDEFGHhIiJLlMmnOopqRSsUVvwXxZz]

The rsync man page has a solution I’ve never seen before: it keeps its SYNOPSIS very terse, like this:

 Local:
     rsync [OPTION...] SRC... [DEST]

and then has an “OPTIONS SUMMARY” section with a 1-line summary of each option, like this:

--verbose, -v            increase verbosity
--info=FLAGS             fine-grained informational verbosity
--debug=FLAGS            fine-grained debug verbosity
--stderr=e|a|c           change stderr output mode (default: errors)
--quiet, -q              suppress non-error messages
--no-motd                suppress daemon-mode MOTD

Then later there’s the usual OPTIONS section with a full description of each option.

an OPTIONS section organized by category

The strace man page organizes its options by category (like “General”, “Startup”, “Tracing”, and “Filtering”, “Output Format”) instead of alphabetically.

As an experiment I tried to take the grep man page and make an “OPTIONS SUMMARY” section grouped by category, you can see the results here. I’m not sure what I think of the results but it was a fun exercise. When I was writing that I was thinking about how I can never remember the name of the -l grep option. It always takes me what feels like forever to find it in the man page and I was trying to think of what structure would make it easier for me to find. Maybe categories?

a cheat sheet

A couple of people pointed me to the suite of Perl man pages (perlfunc, perlre, etc), and one thing I noticed was man perlcheat, which has cheat sheet sections like this:

 SYNTAX
 foreach (LIST) { }     for (a;b;c) { }
 while   (e) { }        until (e)   { }
 if      (e) { } elsif (e) { } else { }
 unless  (e) { } elsif (e) { } else { }
 given   (e) { when (e) {} default {} }

I think this is so cool and it makes me wonder if there are other ways to write condensed ASCII 80-character-wide cheat sheets for use in man pages.

examples are very popular

A common comment was something to the effect of “I like any man page that has examples”. Someone mentioned the OpenBSD man pages, and the openbsd tail man page has examples of the exact 2 ways I use tail at the end.

I think I’ve most often seen the EXAMPLES section at the end of the man page, but some man pages (like the rsync man page from earlier) start with the examples. When I was working on the git-add and git rebase man pages I put a short example at the beginning.

a table of contents, and links between sections

This isn’t a property of the man page itself, but one issue with man pages in the terminal is it’s hard to know what sections the man page has.

When working on the Git man pages, one thing Marie and I did was to add a table of contents to the sidebar of the HTML versions of the man pages hosted on the Git site.

I’d also like to add more hyperlinks to the HTML versions of the Git man pages at some point, so that you can click on “INCOMPATIBLE OPTIONS” to get to that section. It’s very easy to add links like this in the Git project since Git’s man pages are generated with AsciiDoc.

I think adding a table of contents and adding internal hyperlinks is kind of a nice middle ground where we can make some improvements to the man page format (in the HTML version of the man page at least) without maintaining a totally different form of documentation. Though for this to work you do need to set up a toolchain like Git’s AsciiDoc system.

It would be amazing if there were some kind of universal system to make it easy to look up a specific option in a man page (“what does -a do?”). The best trick I know is use the man pager to search for something like ^ *-a but I never remember to do it and instead just end up going through every instance of -a in the man page until I find what I’m looking for.

examples for every option

The curl man page has examples for every option, and there’s also a table of contents on the HTML version so you can more easily jump to the option you’re interested in.

For instance the example for --cert makes it easy to see that you likely also want to pass the --key option, like this:

  curl --cert certfile --key keyfile https://example.com

The way they implement this is that there’s [one file for each option](https://github.com/curl/curl/blob/dc08922a61efe546b318daf964514ffbf41583 25/docs/cmdline-opts/append.md) and there’s an “Example” field in that file.

formatting data in a table

Quite a few people said that man ascii was their favourite man page, which looks like this:

 Oct   Dec   Hex   Char                     
 ───────────────────────────────────────────
 000   0     00    NUL '\0' (null character)
 001   1     01    SOH (start of heading)   
 002   2     02    STX (start of text)      
 003   3     03    ETX (end of text)        
 004   4     04    EOT (end of transmission)
 005   5     05    ENQ (enquiry)            
 006   6     06    ACK (acknowledge)        
 007   7     07    BEL '\a' (bell)          
 010   8     08    BS  '\b' (backspace)     
 011   9     09    HT  '\t' (horizontal tab)
 012   10    0A    LF  '\n' (new line)      

Obviously man ascii is an unusual man page but I think what’s cool about this man page (other than the fact that it’s always useful to have an ASCII reference) is it’s very easy to scan to find the information you need because of the table format. It makes me wonder if there are more opportunities to display information in a “table” in a man page to make it easier to scan.

the GNU approach

When I talk about man pages it often comes up that the GNU coreutils man pages (for example man tail) don’t have examples, unlike the OpenBSD man pages, which do have examples.

I’m not going to get into this too much because it seems like a fairly political topic and I definitely can’t do it justice here, but here are some things I believe to be true:

• The GNU project prefers to maintain documentation in “info” manuals instead of man pages. This page says “the man pages are no longer being maintained”.
• There are 3 ways to read “info” manuals: their HTML version, in Emacs, or with a standalone info tool. I’ve heard from some Emacs users that they like the Emacs info browser. I don’t think I’ve ever talked to anyone who uses the standalone info tool.
• The info manual entry for tail is linked at the bottom of the man page, and it does have examples
• The FSF used to sell print books of the GNU software manuals (and maybe they still do sometimes?)

After a certain level of complexity a man page gets really hard to navigate: while I’ve never used the coreutils info manual and probably won’t, I would almost certainly prefer to use the GNU Bash reference manual or the The GNU C Library Reference Manual via their HTML documentation rather than through a man page.

a few more man-page-adjacent things

Here are some tools I think are interesting:

• The fish shell comes with a Python script to automatically generate tab completions from man pages
• tldr.sh is a community maintained database of examples, for example you can run it as tldr grep. Lots of people have told me they find it useful.
• the Dash Mac docs browser has a nice man page viewer in it. I still use the terminal man page viewer but I like that it includes a table of contents, it looks like this:

it’s interesting to think about a constrained format

Man pages are such a constrained format and it’s fun to think about what you can do with such limited formatting options.

Even though I’m very into writing I’ve always had a bad habit of never reading documentation and so it’s a little bit hard for me to think about what I actually find useful in man pages, I’m not sure whether I think most of the things in this post would improve my experience or not. (Except for examples, I LOVE examples)

So I’d be interested to hear about other man pages that you think are well designed and what you like about them, the comments section is here.

I’ve thought it would be cool to learn a popular web framework like Rails or Django or Laravel for a long time, but I’d never really managed to make it happen. But I started learning Django to make a website a few months back, I’ve been liking it so far, and here are a few quick notes!

less magic than Rails

I spent some time trying to learn Rails in 2020, and while it was cool and I really wanted to like Rails (the Ruby community is great!), I found that if I left my Rails project alone for months, when I came back to it it was hard for me to remember how to get anything done because (for example) if it says resources :topics in your routes.rb, on its own that doesn’t tell you where the topics routes are configured, you need to remember or look up the convention.

Being able to abandon a project for months or years and then come back to it is really important to me (that’s how all my projects work!), and Django feels easier to me because things are more explicit.

In my small Django project it feels like I just have 5 main files (other than the settings files): urls.py, models.py, views.py, admin.py, and tests.py, and if I want to know where something else is (like an HTML template) is then it’s usually explicitly referenced from one of those files.

a built-in admin

For this project I wanted to have an admin interface to manually edit or view some of the data in the database. Django has a really nice built-in admin interface, and I can customize it with just a little bit of code.

For example, here’s part of one of my admin classes, which sets up which fields to display in the “list” view, which field to search on, and how to order them by default.

@admin.register(Zine)
class ZineAdmin(admin.ModelAdmin):
    list_display = ["name", "publication_date", "free", "slug", "image_preview"]
    search_fields = ["name", "slug"]
    readonly_fields = ["image_preview"]
    ordering = ["-publication_date"]

it’s fun to have an ORM

In the past my attitude has been “ORMs? Who needs them? I can just write my own SQL queries!”. I’ve been enjoying Django’s ORM so far though, and I think it’s cool how Django uses __ to represent a JOIN, like this:

Zine.objects
    .exclude(product__order__email_hash=email_hash)

This query involves 5 tables: zines, zine_products, products, order_products, and orders. To make this work I just had to tell Django that there’s a ManyToManyField relating “orders” and “products”, and another ManyToManyField relating “zines”, and “products”, so that it knows how to connect zines, orders, products.

I definitely could write that query, but writing product__order__email_hash is a lot less typing, it feels a lot easier to read, and honestly I think it would take me a little while to figure out how to construct the query (which needs to do a few other things than just those joins).

I have zero concern about the performance of my ORM-generated queries so I’m pretty excited about ORMs for now, though I’m sure I’ll find things to be frustrated with eventually.

automatic migrations!

The other great thing about the ORM is migrations!

If I add, delete, or change a field in models.py, Django will automatically generate a migration script like migrations/0006_delete_imageblob.py.

I assume that I could edit those scripts if I wanted, but so far I’ve just been running the generated scripts with no change and it’s been going great. It really feels like magic.

I’m realizing that being able to do migrations easily is important for me right now because I’m changing my data model fairly often as I figure out how I want it to work.

I like the docs

I had a bad habit of never reading the documentation but I’ve been really enjoying the parts of Django’s docs that I’ve read so far. This isn’t by accident: Jacob Kaplan-Moss has a talk from PyCon 2011 on Django’s documentation culture.

For example the intro to models lists the most important common fields you might want to set when using the ORM.

using sqlite

After having a bad experience trying to operate Postgres and not being able to understand what was going on, I decided to run all of my small websites with SQLite instead. It’s been going way better, and I love being able to backup by just doing a VACUUM INTO and then copying the resulting single file.

I’ve been following these instructions for using SQLite with Django in production.

I think it should be fine because I’m expecting the site to have a few hundred writes per day at most, much less than Mess with DNS which has a lot more of writes and has been working well (though the writes are split across 3 different SQLite databases).

built in email (and more)

Django seems to be very “batteries-included”, which I love – if I want CSRF protection, or a Content-Security-Policy, or I want to send email, it’s all in there!

For example, I wanted to save the emails Django sends to a file in dev mode (so that it didn’t send real email to real people), which was just a little bit of configuration.

I just put this settings/dev.py:

EMAIL_BACKEND = "django.core.mail.backends.filebased.EmailBackend"
EMAIL_FILE_PATH = BASE_DIR / "emails"

and then set up the production email like this in settings/production.py

EMAIL_BACKEND = "django.core.mail.backends.smtp.EmailBackend"
EMAIL_HOST = "smtp.whatever.com"
EMAIL_PORT = 587
EMAIL_USE_TLS = True
EMAIL_HOST_USER = "xxxx"
EMAIL_HOST_PASSWORD = os.getenv('EMAIL_API_KEY')

That made me feel like if I want some other basic website feature, there’s likely to be an easy way to do it built into Django already.

the settings file still feels like a lot

I’m still a bit intimidated by the settings.py file: Django’s settings system works by setting a bunch of global variables in a file, and I feel a bit stressed about… what if I make a typo in the name of one of those variables? How will I know? What if I type WSGI_APPLICATOIN = "config.wsgi.application" instead of WSGI_APPLICATION?

I guess I’ve gotten used to having a Python language server tell me when I’ve made a typo and so now it feels a bit disorienting when I can’t rely on the language server support.

that’s all for now!

I haven’t really successfully used an actual web framework for a project before (right now almost all of my websites are either a single Go binary or static sites), so I’m interested in seeing how it goes!

There’s still lots for me to learn about, I still haven’t really gotten into Django’s form validation tooling or authentication systems.

Thanks to Marco Rogers for convincing me to give ORMs a chance.

(we’re still experimenting with the comments-on-Mastodon system! Here are the comments on Mastodon! tell me your favourite Django feature!)

So Marie and I made a few changes to the Git documentation!

a data model for Git

After a while working on the documentation, we noticed that Git uses the terms “object”, “reference”, or “index” in its documentation a lot, but that it didn’t have a great explanation of what those terms mean or how they relate to other core concepts like “commit” and “branch”. So we wrote a new “data model” document!

You can read the data model here for now. I assume at some point (after the next release?) it’ll also be on the Git website.

I’m excited about this because understanding how Git organizes its commit and branch data has really helped me reason about how Git works over the years, and I think it’s important to have a short (1600 words!) version of the data model that’s accurate.

The “accurate” part turned out to not be that easy: I knew the basics of how Git’s data model worked, but during the review process I learned some new details and had to make quite a few changes (for example how merge conflicts are stored in the staging area).

updates to git push, git pull, and more

I also worked on updating the introduction to some of Git’s core man pages. I quickly realized that “just try to improve it according to my best judgement” was not going to work: why should the maintainers believe me that my version is better?

I’ve seen a problem a lot when discussing open source documentation changes where 2 expert users of the software argue about whether an explanation is clear or not (“I think X would be a good way to explain it! Well, I think Y would be better!”)

I don’t think this is very productive (expert users of a piece of software are notoriously bad at being able to tell if an explanation will be clear to non-experts), so I needed to find a way to identify problems with the man pages that was a little more evidence-based.

getting test readers to identify problems

I asked for test readers on Mastodon to read the current version of documentation and tell me what they find confusing or what questions they have. About 80 test readers left comments, and I learned so much!

People left a huge amount of great feedback, for example:

• terminology they didn’t understand (what’s a pathspec? what does “reference” mean? does “upstream” have a specific meaning in Git?)
• specific confusing sentences
• suggestions of things things to add (“I do X all the time, I think it should be included here”)
• inconsistencies (“here it implies X is the default, but elsewhere it implies Y is the default”)

Most of the test readers had been using Git for at least 5-10 years, which I think worked well – if a group of test readers who have been using Git regularly for 5+ years find a sentence or term impossible to understand, it makes it easy to argue that the documentation should be updated to make it clearer.

I thought this “get users of the software to comment on the existing documentation and then fix the problems they find” pattern worked really well and I’m excited about potentially trying it again in the future.

the man page changes

We ended updating these 4 man pages:

• git add (before, after)
• git checkout (before, after)
• git push (before, after)
• git pull (before, after)

The git push and git pull changes were the most interesting to me: in addition to updating the intro to those pages, we also ended up writing:

• a section describing what the term “upstream branch” means (which previously wasn’t really explained)
• a cleaned-up description of what a “push refspec” is

Making those changes really gave me an appreciation for how much work it is to maintain open source documentation: it’s not easy to write things that are both clear and true, and sometimes we had to make compromises, for example the sentence “git push may fail if you haven’t set an upstream for the current branch, depending on what push.default is set to.” is a little vague, but the exact details of what “depending” means are really complicated and untangling that is a big project.

on the process for contributing to Git

It took me a while to understand Git’s development process. I’m not going to try to describe it here (that could be a whole other post!), but a few quick notes:

• Git has a Discord server with a “my first contribution” channel for help with getting started contributing. I found people to be very welcoming on the Discord.
• I used GitGitGadget to make all of my contributions. This meant that I could make a GitHub pull request (a workflow I’m comfortable with) and GitGitGadget would convert my PRs into the system the Git developers use (emails with patches attached). GitGitGadget worked great and I was very grateful to not have to learn how to send patches by email with Git.
• Otherwise I used my normal email client (Fastmail’s web interface) to reply to emails, wrapping my text to 80 character lines since that’s the mailing list norm.

I also found the mailing list archives on lore.kernel.org hard to navigate, so I hacked together my own git list viewer to make it easier to read the long mailing list threads.

Many people helped me navigate the contribution process and review the changes: thanks to Emily Shaffer, Johannes Schindelin (the author of GitGitGadget), Patrick Steinhardt, Ben Knoble, Junio Hamano, and more.

(I’m experimenting with comments on Mastodon, you can see the comments here)

I’ve been using it for 3 months now and here are a few notes.

why helix: language servers

I think what motivated me to try Helix is that I’ve been trying to get a working language server setup (so I can do things like “go to definition”) and getting a setup that feels good in Vim or Neovim just felt like too much work.

After using Vim/Neovim for 20 years, I’ve tried both “build my own custom configuration from scratch” and “use someone else’s pre-buld configuration system” and even though I love Vim I was excited about having things just work without having to work on my configuration at all.

Helix comes with built in language server support, and it feels nice to be able to do things like “rename this symbol” in any language.

the search is great

One of my favourite things about Helix is the search! If I’m searching all the files in my repository for a string, it lets me scroll through the potential matching files and see the full context of the match, like this:

For comparison, here’s what the vim ripgrep plugin I’ve been using looks like:

There’s no context for what else is around that line.

the quick reference is nice

One thing I like about Helix is that when I press g, I get a little help popup telling me places I can go. I really appreciate this because I don’t often use the “go to definition” or “go to reference” feature and I often forget the keyboard shortcut.

some vim -> helix translations

• Helix doesn’t have marks like ma, 'a, instead I’ve been using Ctrl+O and Ctrl+I to go back (or forward) to the last cursor location
• I think Helix does have macros, but I’ve been using multiple cursors in every case that I would have previously used a macro. I like multiple cursors a lot more than writing macros all the time. If I want to batch change something in the document, my workflow is to press % (to highlight everything), then s to select (with a regex) the things I want to change, then I can just edit all of them as needed.
• Helix doesn’t have neovim-style tabs, instead it has a nice buffer switcher (<space>b) I can use to switch to the buffer I want. There’s a pull request here to implement neovim-style tabs. There’s also a setting bufferline="multiple" which can act a bit like tabs with gp, gn for prev/next “tab” and :bc to close a “tab”.

some helix annoyances

Here’s everything that’s annoyed me about Helix so far.

• I like the way Helix’s :reflow works much less than how vim reflows text with gq. It doesn’t work as well with lists. (github issue)
• If I’m making a Markdown list, pressing “enter” at the end of a list item won’t continue the list. There’s a partial workaround for bulleted lists but I don’t know one for numbered lists.
• No persistent undo yet: in vim I could use an undofile so that I could undo changes even after quitting. Helix doesn’t have that feature yet. (github PR)
• Helix doesn’t autoreload files after they change on disk, I have to run :reload-all (:ra<tab>) to manually reload them. Not a big deal.
• Sometimes it crashes, maybe every week or so. I think it might be this issue.

The “markdown list” and reflowing issues come up a lot for me because I spend a lot of time editing Markdown lists, but I keep using Helix anyway so I guess they can’t be making me that mad.

switching was easier than I thought

I was worried that relearning 20 years of Vim muscle memory would be really hard.

It turned out to be easier than I expected, I started using Helix on a vacation for a little low-stakes coding project I was doing on the side and after a week or two it didn’t feel so disorienting anymore. I think it might be hard to switch back and forth between Vim and Helix, but I haven’t needed to use Vim recently so I don’t know if that’ll ever become an issue for me.

The first time I tried Helix I tried to force it to use keybindings that were more similar to Vim and that did not work for me. Just learning the “Helix way” was a lot easier.

There are still some things that throw me off: for example w in vim and w in Helix don’t have the same idea of what a “word” is (the Helix one includes the space after the word, the Vim one doesn’t).

using a terminal-based text editor

For many years I’d mostly been using a GUI version of vim/neovim, so switching to actually using an editor in the terminal was a bit of an adjustment.

I ended up deciding on:

1. Every project gets its own terminal window, and all of the tabs in that window (mostly) have the same working directory
2. I make my Helix tab the first tab in the terminal window

It works pretty well, I might actually like it better than my previous workflow.

my configuration

I appreciate that my configuration is really simple, compared to my neovim configuration which is hundreds of lines. It’s mostly just 4 keyboard shortcuts.

theme = "solarized_light"
[editor]
# Sync clipboard with system clipboard
default-yank-register = "+"

[keys.normal]
# I didn't like that Ctrl+C was the default "toggle comments" shortcut
"#" = "toggle_comments"

# I didn't feel like learning a different way
# to go to the beginning/end of a line so
# I remapped ^ and $
"^" = "goto_first_nonwhitespace"
"$" = "goto_line_end"

[keys.select]
"^" = "goto_first_nonwhitespace"
"$" = "goto_line_end"

[keys.normal.space]
# I write a lot of text so I need to constantly reflow,
# and missed vim's `gq` shortcut
l = ":reflow"

There’s a separate languages.toml configuration where I set some language preferences, like turning off autoformatting. For example, here’s my Python configuration:

[[language]]
name = "python"
formatter = { command = "black", args = ["--stdin-filename", "%{buffer_name}", "-"] }
language-servers = ["pyright"]
auto-format = false

we’ll see how it goes

Three months is not that long, and it’s possible that I’ll decide to go back to Vim at some point. For example, I wrote a post about switching to nix a while back but after maybe 8 months I switched back to Homebrew (though I’m still using NixOS to manage one little server, and I’m still satisfied with that).

You can get it for $12 here: https://wizardzines.com/zines/terminal, or get an 15-pack of all my zines here.

Here’s the cover:

the table of contents

Here’s the table of contents:

why the terminal?

I’ve been using the terminal every day for 20 years but even though I’m very confident in the terminal, I’ve always had a bit of an uneasy feeling about it. Usually things work fine, but sometimes something goes wrong and it just feels like investigating it is impossible, or at least like it would open up a huge can of worms.

So I started trying to write down a list of weird problems I’ve run into in terminal and I realized that the terminal has a lot of tiny inconsistencies like:

• sometimes you can use the arrow keys to move around, but sometimes pressing the arrow keys just prints ^[[D
• sometimes you can use the mouse to select text, but sometimes you can’t
• sometimes your commands get saved to a history when you run them, and sometimes they don’t
• some shells let you use the up arrow to see the previous command, and some don’t

If you use the terminal daily for 10 or 20 years, even if you don’t understand exactly why these things happen, you’ll probably build an intuition for them.

But having an intuition for them isn’t the same as understanding why they happen. When writing this zine I actually had to do a lot of work to figure out exactly what was happening in the terminal to be able to talk about how to reason about it.

the rules aren’t written down anywhere

It turns out that the “rules” for how the terminal works (how do you edit a command you type in? how do you quit a program? how do you fix your colours?) are extremely hard to fully understand, because “the terminal” is actually made of many different pieces of software (your terminal emulator, your operating system, your shell, the core utilities like grep, and every other random terminal program you’ve installed) which are written by different people with different ideas about how things should work.

So I wanted to write something that would explain:

• how the 4 pieces of the terminal (your shell, terminal emulator, programs, and TTY driver) fit together to make everything work
• some of the core conventions for how you can expect things in your terminal to work
• lots of tips and tricks for how to use terminal programs

this zine explains the most useful parts of terminal internals

Terminal internals are a mess. A lot of it is just the way it is because someone made a decision in the 80s and now it’s impossible to change, and honestly I don’t think learning everything about terminal internals is worth it.

But some parts are not that hard to understand and can really make your experience in the terminal better, like:

• if you understand what your shell is responsible for, you can configure your shell (or use a different one!) to access your history more easily, get great tab completion, and so much more
• if you understand escape codes, it’s much less scary when cating a binary to stdout messes up your terminal, you can just type reset and move on
• if you understand how colour works, you can get rid of bad colour contrast in your terminal so you can actually read the text

I learned a surprising amount writing this zine

When I wrote How Git Works, I thought I knew how Git worked, and I was right. But the terminal is different. Even though I feel totally confident in the terminal and even though I’ve used it every day for 20 years, I had a lot of misunderstandings about how the terminal works and (unless you’re the author of tmux or something) I think there’s a good chance you do too.

A few things I learned that are actually useful to me:

• I understand the structure of the terminal better and so I feel more confident debugging weird terminal stuff that happens to me (I was even able to suggest a small improvement to fish!). Identifying exactly which piece of software is causing a weird thing to happen in my terminal still isn’t easy but I’m a lot better at it now.
• you can write a shell script to copy to your clipboard over SSH
• how reset works under the hood (it does the equivalent of stty sane; sleep 1; tput reset) – basically I learned that I don’t ever need to worry about remembering stty sane or tput reset and I can just run reset instead
• how to look at the invisible escape codes that a program is printing out (run unbuffer program > out; less out)
• why the builtin REPLs on my Mac like sqlite3 are so annoying to use (they use libedit instead of readline)

blog posts I wrote along the way

As usual these days I wrote a bunch of blog posts about various side quests:

• How to add a directory to your PATH
• “rules” that terminal problems follow
• why pipes sometimes get “stuck”: buffering
• some terminal frustrations
• ASCII control characters in my terminal on “what’s the deal with Ctrl+A, Ctrl+B, Ctrl+C, etc?”
• entering text in the terminal is complicated
• what’s involved in getting a “modern” terminal setup?
• reasons to use your shell’s job control
• standards for ANSI escape codes, which is really me trying to figure out if I think the terminfo database is serving us well today

people who helped with this zine

A long time ago I used to write zines mostly by myself but with every project I get more and more help. I met with Marie Claire LeBlanc Flanagan every weekday from September to June to work on this one.

The cover is by Vladimir Kašiković, Lesley Trites did copy editing, Simon Tatham (who wrote PuTTY) did technical review, our Operations Manager Lee did the transcription as well as a million other things, and Jesse Luehrs (who is one of the very few people I know who actually understands the terminal’s cursed inner workings) had so many incredibly helpful conversations with me about what is going on in the terminal.

get the zine

Here are some links to get the zine again:

• get The Secret Rules of the Terminal
• get a 15-pack of all my zines here.

As always, you can get either a PDF version to print at home or a print version shipped to your house. The only caveat is print orders will ship in August – I need to wait for orders to come in to get an idea of how many I should print before sending it to the printer.

“Hope someone else has compiled it” worked pretty well when I was running Linux but since I’ve been using a Mac for the last couple of years I’ve been running into more situations where I have to actually compile programs myself.

So let’s talk about what you might have to do to compile a C program! I’ll use a couple of examples of specific C programs I’ve compiled and talk about a few things that can go wrong. Here are three programs we’ll be talking about compiling:

• paperjam
• sqlite
• qf (a pager you can run to quickly open files from a search with rg -n THING | qf)

step 1: install a C compiler

This is pretty simple: on an Ubuntu system if I don’t already have a C compiler I’ll install one with:

sudo apt-get install build-essential

This installs gcc, g++, and make. The situation on a Mac is more confusing but it’s something like “install xcode command line tools”.

step 2: install the program’s dependencies

Unlike some newer programming languages, C doesn’t have a dependency manager. So if a program has any dependencies, you need to hunt them down yourself. Thankfully because of this, C programmers usually keep their dependencies very minimal and often the dependencies will be available in whatever package manager you’re using.

There’s almost always a section explaining how to get the dependencies in the README, for example in paperjam’s README, it says:

To compile PaperJam, you need the headers for the libqpdf and libpaper libraries (usually available as libqpdf-dev and libpaper-dev packages).

You may need a2x (found in AsciiDoc) for building manual pages.

So on a Debian-based system you can install the dependencies like this.

sudo apt install -y libqpdf-dev libpaper-dev

If a README gives a name for a package (like libqpdf-dev), I’d basically always assume that they mean “in a Debian-based Linux distro”: if you’re on a Mac brew install libqpdf-dev will not work. I still have not 100% gotten the hang of developing on a Mac yet so I don’t have many tips there yet. I guess in this case it would be brew install qpdf if you’re using Homebrew.

step 3: run ./configure (if needed)

Some C programs come with a Makefile and some instead come with a script called ./configure. For example, if you download sqlite’s source code, it has a ./configure script in it instead of a Makefile.

My understanding of this ./configure script is:

1. You run it, it prints out a lot of somewhat inscrutable output, and then it either generates a Makefile or fails because you’re missing some dependency
2. The ./configure script is part of a system called autotools that I have never needed to learn anything about beyond “run it to generate a Makefile”.

I think there might be some options you can pass to get the ./configure script to produce a different Makefile but I have never done that.

step 4: run make

The next step is to run make to try to build a program. Some notes about make:

• Sometimes you can run make -j8 to parallelize the build and make it go faster
• It usually prints out a million compiler warnings when compiling the program. I always just ignore them. I didn’t write the software! The compiler warnings are not my problem.

compiler errors are often dependency problems

Here’s an error I got while compiling paperjam on my Mac:

/opt/homebrew/Cellar/qpdf/12.0.0/include/qpdf/InputSource.hh:85:19: error: function definition does not declare parameters
   85 |     qpdf_offset_t last_offset{0};
      |                   ^

Over the years I’ve learned it’s usually best not to overthink problems like this: if it’s talking about qpdf, there’s a good change it just means that I’ve done something wrong with how I’m including the qpdf dependency.

Now let’s talk about some ways to get the qpdf dependency included in the right way.

the world’s shortest introduction to the compiler and linker

Before we talk about how to fix dependency problems: building C programs is split into 2 steps:

1. Compiling the code into object files (with gcc or clang)
2. Linking those object files into a final binary (with ld)

It’s important to know this when building a C program because sometimes you need to pass the right flags to the compiler and linker to tell them where to find the dependencies for the program you’re compiling.

make uses environment variables to configure the compiler and linker

If I run make on my Mac to install paperjam, I get this error:

c++ -o paperjam paperjam.o pdf-tools.o parse.o cmds.o pdf.o -lqpdf -lpaper
ld: library 'qpdf' not found

This is not because qpdf is not installed on my system (it actually is!). But the compiler and linker don’t know how to find the qpdf library. To fix this, we need to:

• pass "-I/opt/homebrew/include" to the compiler (to tell it where to find the header files)
• pass "-L/opt/homebrew/lib -liconv" to the linker (to tell it where to find library files and to link in iconv)

And we can get make to pass those extra parameters to the compiler and linker using environment variables! To see how this works: inside paperjam’s Makefile you can see a bunch of environment variables, like LDLIBS here:

paperjam: $(OBJS)
	$(LD) -o $@ $^ $(LDLIBS)

Everything you put into the LDLIBS environment variable gets passed to the linker (ld) as a command line argument.

secret environment variable: CPPFLAGS

Makefiles sometimes define their own environment variables that they pass to the compiler/linker, but make also has a bunch of “implicit” environment variables which it will automatically pass to the C compiler and linker. There’s a full list of implicit environment variables here, but one of them is CPPFLAGS, which gets automatically passed to the C compiler.

(technically it would be more normal to use CXXFLAGS for this, but this particular Makefile hardcodes CXXFLAGS so setting CPPFLAGS was the only way I could find to set the compiler flags without editing the Makefile)

two ways to pass environment variables to make

I learned thanks to @zwol that there are actually two ways to pass environment variables to make:

1. CXXFLAGS=xyz make (the usual way)
2. make CXXFLAGS=xyz

The difference between them is that make CXXFLAGS=xyz will override the value of CXXFLAGS set in the Makefile but CXXFLAGS=xyz make won’t.

I’m not sure which way is the norm but I’m going to use the first way in this post.

how to use CPPFLAGS and LDLIBS to fix this compiler error

Now that we’ve talked about how CPPFLAGS and LDLIBS get passed to the compiler and linker, here’s the final incantation that I used to get the program to build successfully!

CPPFLAGS="-I/opt/homebrew/include" LDLIBS="-L/opt/homebrew/lib -liconv" make paperjam

This passes -I/opt/homebrew/include to the compiler and -L/opt/homebrew/lib -liconv to the linker.

Also I don’t want to pretend that I “magically” knew that those were the right arguments to pass, figuring them out involved a bunch of confused Googling that I skipped over in this post. I will say that:

• the -I compiler flag tells the compiler which directory to find header files in, like /opt/homebrew/include/qpdf/QPDF.hh
• the -L linker flag tells the linker which directory to find libraries in, like /opt/homebrew/lib/libqpdf.a
• the -l linker flag tells the linker which libraries to link in, like -liconv means “link in the iconv library”, or -lm means “link math”

tip: how to just build 1 specific file: make $FILENAME

Yesterday I discovered this cool tool called qf which you can use to quickly open files from the output of ripgrep.

qf is in a big directory of various tools, but I only wanted to compile qf. So I just compiled qf, like this:

make qf

Basically if you know (or can guess) the output filename of the file you’re trying to build, you can tell make to just build that file by running make $FILENAME

tip: you don’t need a Makefile

I sometimes write 5-line C programs with no dependencies, and I just learned that if I have a file called blah.c, I can just compile it like this without creating a Makefile:

make blah

It gets automaticaly expanded to cc -o blah blah.c, which saves a bit of typing. I have no idea if I’m going to remember this (I might just keep typing gcc -o blah blah.c anyway) but it seems like a fun trick.

tip: look at how other packaging systems built the same C program

If you’re having trouble building a C program, maybe other people had problems building it too! Every Linux distribution has build files for every package that they build, so even if you can’t install packages from that distribution directly, maybe you can get tips from that Linux distro for how to build the package. Realizing this (thanks to my friend Dave) was a huge ah-ha moment for me.

For example, this line from the nix package for paperjam says:

  env.NIX_LDFLAGS = lib.optionalString stdenv.hostPlatform.isDarwin "-liconv";

This is basically saying “pass the linker flag -liconv to build this on a Mac”, so that’s a clue we could use to build it.

That same file also says env.NIX_CFLAGS_COMPILE = "-DPOINTERHOLDER_TRANSITION=1";. I’m not sure what this means, but when I try to build the paperjam package I do get an error about something called a PointerHolder, so I guess that’s somehow related to the “PointerHolder transition”.

step 5: installing the binary

Once you’ve managed to compile the program, probably you want to install it somewhere! Some Makefiles have an install target that let you install the tool on your system with make install. I’m always a bit scared of this (where is it going to put the files? what if I want to uninstall them later?), so if I’m compiling a pretty simple program I’ll often just manually copy the binary to install it instead, like this:

cp qf ~/bin

step 6: maybe make your own package!

Once I figured out how to do all of this, I realized that I could use my new make knowledge to contribute a paperjam package to Homebrew! Then I could just brew install paperjam on future systems.

The good thing is that even if the details of how all of the different packaging systems, they fundamentally all use C compilers and linkers.

it can be useful to understand a little about C even if you’re not a C programmer

I think all of this is an interesting example of how it can useful to understand some basics of how C programs work (like “they have header files”) even if you’re never planning to write a nontrivial C program if your life.

It feels good to have some ability to compile C/C++ programs myself, even though I’m still not totally confident about all of the compiler and linker flags and I still plan to never learn anything about how autotools works other than “you run ./configure to generate the Makefile”.

Two things I left out of this post:

• LD_LIBRARY_PATH / DYLD_LIBRARY_PATH (which you use to tell the dynamic linker at runtime where to find dynamically linked files) because I can’t remember the last time I ran into an LD_LIBRARY_PATH issue and couldn’t find an example.
• pkg-config, which I think is important but I don’t understand yet

For a long time I was vaguely aware of ANSI escape codes (“that’s how you make text red in the terminal and stuff”) but I had no real understanding of where they were supposed to be defined or whether or not there were standards for them. I just had a kind of vague “there be dragons” feeling around them. While learning about the terminal this year, I’ve learned that:

1. ANSI escape codes are responsible for a lot of usability improvements in the terminal (did you know there’s a way to copy to your system clipboard when SSHed into a remote machine?? It’s an escape code called OSC 52!)
2. They aren’t completely standardized, and because of that they don’t always work reliably. And because they’re also invisible, it’s extremely frustrating to troubleshoot escape code issues.

So I wanted to put together a list for myself of some standards that exist around escape codes, because I want to know if they have to feel unreliable and frustrating, or if there’s a future where we could all rely on them with more confidence.

• what’s an escape code?
• ECMA-48
• xterm control sequences
• terminfo
• should programs use terminfo?
• is there a “single common set” of escape codes?
• some reasons to use terminfo
• some more documents/standards
• why I think this is interesting

what’s an escape code?

Have you ever pressed the left arrow key in your terminal and seen ^[[D? That’s an escape code! It’s called an “escape code” because the first character is the “escape” character, which is usually written as ESC, \x1b, \E, \033, or ^[.

Escape codes are how your terminal emulator communicates various kinds of information (colours, mouse movement, etc) with programs running in the terminal. There are two kind of escape codes:

1. input codes which your terminal emulator sends for keypresses or mouse movements that don’t fit into Unicode. For example “left arrow key” is ESC[D, “Ctrl+left arrow” might be ESC[1;5D, and clicking the mouse might be something like ESC[M :3.
2. output codes which programs can print out to colour text, move the cursor around, clear the screen, hide the cursor, copy text to the clipboard, enable mouse reporting, set the window title, etc.

Now let’s talk about standards!

ECMA-48

The first standard I found relating to escape codes was ECMA-48, which was originally published in 1976.

ECMA-48 does two things:

1. Define some general formats for escape codes (like “CSI” codes, which are ESC[ + something and “OSC” codes, which are ESC] + something)
2. Define some specific escape codes, like how “move the cursor to the left” is ESC[D, or “turn text red” is ESC[31m. In the spec, the “cursor left” one is called CURSOR LEFT and the one for changing colours is called SELECT GRAPHIC RENDITION.

The formats are extensible, so there’s room for others to define more escape codes in the future. Lots of escape codes that are popular today aren’t defined in ECMA-48: for example it’s pretty common for terminal applications (like vim, htop, or tmux) to support using the mouse, but ECMA-48 doesn’t define escape codes for the mouse.

xterm control sequences

There are a bunch of escape codes that aren’t defined in ECMA-48, for example:

• enabling mouse reporting (where did you click in your terminal?)
• bracketed paste (did you paste that text or type it in?)
• OSC 52 (which terminal applications can use to copy text to your system clipboard)

I believe (correct me if I’m wrong!) that these and some others came from xterm, are documented in XTerm Control Sequences, and have been widely implemented by other terminal emulators.

This list of “what xterm supports” is not a standard exactly, but xterm is extremely influential and so it seems like an important document.

terminfo

In the 80s (and to some extent today, but my understanding is that it was MUCH more dramatic in the 80s) there was a huge amount of variation in what escape codes terminals actually supported.

To deal with this, there’s a database of escape codes for various terminals called “terminfo”.

It looks like the standard for terminfo is called X/Open Curses, though you need to create an account to view that standard for some reason. It defines the database format as well as a C library interface (“curses”) for accessing the database.

For example you can run this bash snippet to see every possible escape code for “clear screen” for all of the different terminals your system knows about:

for term in $(toe -a | awk '{print $1}')
do
  echo $term
  infocmp -1 -T "$term" 2>/dev/null | grep 'clear=' | sed 's/clear=//g;s/,//g'
done

On my system (and probably every system I’ve ever used?), the terminfo database is managed by ncurses.

should programs use terminfo?

I think it’s interesting that there are two main approaches that applications take to handling ANSI escape codes:

1. Use the terminfo database to figure out which escape codes to use, depending on what’s in the TERM environment variable. Fish does this, for example.
2. Identify a “single common set” of escape codes which works in “enough” terminal emulators and just hardcode those.

Some examples of programs/libraries that take approach #2 (“don’t use terminfo”) include:

• kakoune
• python-prompt-toolkit
• linenoise
• libvaxis
• chalk

I got curious about why folks might be moving away from terminfo and I found this very interesting and extremely detailed rant about terminfo from one of the fish maintainers, which argues that:

[the terminfo authors] have done a lot of work that, at the time, was extremely important and helpful. My point is that it no longer is.

I’m not going to do it justice so I’m not going to summarize it, I think it’s worth reading.

is there a “single common set” of escape codes?

I was just talking about the idea that you can use a “common set” of escape codes that will work for most people. But what is that set? Is there any agreement?

I really do not know the answer to this at all, but from doing some reading it seems like it’s some combination of:

• The codes that the VT100 supported (though some aren’t relevant on modern terminals)
• what’s in ECMA-48 (which I think also has some things that are no longer relevant)
• What xterm supports (though I’d guess that not everything in there is actually widely supported enough)

and maybe ultimately “identify the terminal emulators you think your users are going to use most frequently and test in those”, the same way web developers do when deciding which CSS features are okay to use

I don’t think there are any resources like Can I use…? or Baseline for the terminal though. (in theory terminfo is supposed to be the “caniuse” for the terminal but it seems like it often takes 10+ years to add new terminal features when people invent them which makes it very limited)

some reasons to use terminfo

I also asked on Mastodon why people found terminfo valuable in 2025 and got a few reasons that made sense to me:

• some people expect to be able to use the TERM environment variable to control how programs behave (for example with TERM=dumb), and there’s no standard for how that should work in a post-terminfo world
• even though there’s less variation between terminal emulators than there was in the 80s, there’s far from zero variation: there are graphical terminals, the Linux framebuffer console, the situation you’re in when connecting to a server via its serial console, Emacs shell mode, and probably more that I’m missing
• there is no one standard for what the “single common set” of escape codes is, and sometimes programs use escape codes which aren’t actually widely supported enough

terminfo & user agent detection

The way that ncurses uses the TERM environment variable to decide which escape codes to use reminds me of how webservers used to sometimes use the browser user agent to decide which version of a website to serve.

It also seems like it’s had some of the same results – the way iTerm2 reports itself as being “xterm-256color” feels similar to how Safari’s user agent is “Mozilla/5.0 (Macintosh; Intel Mac OS X 14_7_4) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.3 Safari/605.1.15”. In both cases the terminal emulator / browser ends up changing its user agent to get around user agent detection that isn’t working well.

On the web we ended up deciding that user agent detection was not a good practice and to instead focus on standardization so we can serve the same HTML/CSS to all browsers. I don’t know if the same approach is the future in the terminal though – I think the terminal landscape today is much more fragmented than the web ever was as well as being much less well funded.

some more documents/standards

A few more documents and standards related to escape codes, in no particular order:

• the Linux console_codes man page documents escape codes that Linux supports
• how the VT 100 handles escape codes & control sequences
• the kitty keyboard protocol
• OSC 8 for links in the terminal (and notes on adoption)
• A summary of ANSI standards from tmux
• this terminal features reporting specification from iTerm
• sixel graphics

why I think this is interesting

I sometimes see people saying that the unix terminal is “outdated”, and since I love the terminal so much I’m always curious about what incremental changes might make it feel less “outdated”.

Maybe if we had a clearer standards landscape (like we do on the web!) it would be easier for terminal emulator developers to build new features and for authors of terminal applications to more confidently adopt those features so that we can all benefit from them and have a richer experience in the terminal.

Obviously standardizing ANSI escape codes is not easy (ECMA-48 was first published almost 50 years ago and we’re still not there!). I don’t even know what all of the challenges are. But the situation with HTML/CSS/JS used to be extremely bad too and now it’s MUCH better, so maybe there’s hope.

So I wanted to try to write down some more complete directions and mention some of the gotchas I’ve run into over the years.

Here’s a table of contents:

• step 1: what shell are you using?
• step 2: find your shell’s config file
  • a note on bash’s config file
• step 3: figure out which directory to add
  • step 3.1: double check it’s the right directory
• step 4: edit your shell config
• step 5: restart your shell
• problems:
  • problem 1: it ran the wrong program
  • problem 2: the program isn’t being run from your shell
  • problem 3: duplicate PATH entries making it harder to debug
  • problem 4: losing your history after updating your PATH
• notes:
  • a note on source
  • a note on fish_add_path

step 1: what shell are you using?

If you’re not sure what shell you’re using, here’s a way to find out. Run this:

ps -p $$ -o pid,comm=

• if you’re using bash, it’ll print out 97295 bash
• if you’re using zsh, it’ll print out 97295 zsh
• if you’re using fish, it’ll print out an error like “In fish, please use $fish_pid” ($$ isn’t valid syntax in fish, but in any case the error message tells you that you’re using fish, which you probably already knew)

Also bash is the default on Linux and zsh is the default on Mac OS (as of 2024). I’ll only cover bash, zsh, and fish in these directions.

step 2: find your shell’s config file

• in zsh, it’s probably ~/.zshrc
• in bash, it might be ~/.bashrc, but it’s complicated, see the note in the next section
• in fish, it’s probably ~/.config/fish/config.fish (you can run echo $__fish_config_dir if you want to be 100% sure)

a note on bash’s config file

Bash has three possible config files: ~/.bashrc, ~/.bash_profile, and ~/.profile.

If you’re not sure which one your system is set up to use, I’d recommend testing this way:

1. add echo hi there to your ~/.bashrc
2. Restart your terminal
3. If you see “hi there”, that means ~/.bashrc is being used! Hooray!
4. Otherwise remove it and try the same thing with ~/.bash_profile
5. You can also try ~/.profile if the first two options don’t work.

(there are a lot of elaborate flow charts out there that explain how bash decides which config file to use but IMO it’s not worth it to internalize them and just testing is the fastest way to be sure)

step 3: figure out which directory to add

Let’s say that you’re trying to install and run a program called http-server and it doesn’t work, like this:

$ npm install -g http-server
$ http-server
bash: http-server: command not found

How do you find what directory http-server is in? Honestly in general this is not that easy – often the answer is something like “it depends on how npm is configured”. A few ideas:

• Often when setting up a new installer (like cargo, npm, homebrew, etc), when you first set it up it’ll print out some directions about how to update your PATH. So if you’re paying attention you can get the directions then.
• Sometimes installers will automatically update your shell’s config file to update your PATH for you
• Sometimes just Googling “where does npm install things?” will turn up the answer
• Some tools have a subcommand that tells you where they’re configured to install things, like:
  • Node/npm: npm config get prefix (then append /bin/)
  • Go: go env GOPATH (then append /bin/)
  • asdf: asdf info | grep ASDF_DIR (then append /bin/ and /shims/)

step 3.1: double check it’s the right directory

Once you’ve found a directory you think might be the right one, make sure it’s actually correct! For example, I found out that on my machine, http-server is in ~/.npm-global/bin. I can make sure that it’s the right directory by trying to run the program http-server in that directory like this:

$ ~/.npm-global/bin/http-server
Starting up http-server, serving ./public

It worked! Now that you know what directory you need to add to your PATH, let’s move to the next step!

step 4: edit your shell config

Now we have the 2 critical pieces of information we need:

1. Which directory you’re trying to add to your PATH (like ~/.npm-global/bin/)
2. Where your shell’s config is (like ~/.bashrc, ~/.zshrc, or ~/.config/fish/config.fish)

Now what you need to add depends on your shell:

bash instructions:

Open your shell’s config file, and add a line like this:

export PATH=$PATH:~/.npm-global/bin/

(obviously replace ~/.npm-global/bin with the actual directory you’re trying to add)

zsh instructions:

You can do the same thing as in bash, but zsh also has some slightly fancier syntax you can use if you prefer:

path=(
  $path
  ~/.npm-global/bin
)

fish instructions:

In fish, the syntax is different:

set PATH $PATH ~/.npm-global/bin

(in fish you can also use fish_add_path, some notes on that further down)

step 5: restart your shell

Now, an extremely important step: updating your shell’s config won’t take effect if you don’t restart it!

Two ways to do this:

1. open a new terminal (or terminal tab), and maybe close the old one so you don’t get confused
2. Run bash to start a new shell (or zsh if you’re using zsh, or fish if you’re using fish)

I’ve found that both of these usually work fine.

And you should be done! Try running the program you were trying to run and hopefully it works now.

If not, here are a couple of problems that you might run into:

problem 1: it ran the wrong program

If the wrong version of a program is running, you might need to add the directory to the beginning of your PATH instead of the end.

For example, on my system I have two versions of python3 installed, which I can see by running which -a:

$ which -a python3
/usr/bin/python3
/opt/homebrew/bin/python3

The one your shell will use is the first one listed.

If you want to use the Homebrew version, you need to add that directory (/opt/homebrew/bin) to the beginning of your PATH instead, by putting this in your shell’s config file (it’s /opt/homebrew/bin/:$PATH instead of the usual $PATH:/opt/homebrew/bin/)

export PATH=/opt/homebrew/bin/:$PATH

or in fish:

set PATH ~/.cargo/bin $PATH

problem 2: the program isn’t being run from your shell

All of these directions only work if you’re running the program from your shell. If you’re running the program from an IDE, from a GUI, in a cron job, or some other way, you’ll need to add the directory to your PATH in a different way, and the exact details might depend on the situation.

in a cron job

Some options:

• use the full path to the program you’re running, like /home/bork/bin/my-program
• put the full PATH you want as the first line of your crontab (something like PATH=/bin:/usr/bin:/usr/local/bin:….). You can get the full PATH you’re using in your shell by running echo "PATH=$PATH".

I’m honestly not sure how to handle it in an IDE/GUI because I haven’t run into that in a long time, will add directions here if someone points me in the right direction.

problem 3: duplicate PATH entries making it harder to debug

If you edit your path and start a new shell by running bash (or zsh, or fish), you’ll often end up with duplicate PATH entries, because the shell keeps adding new things to your PATH every time you start your shell.

Personally I don’t think I’ve run into a situation where this kind of duplication breaks anything, but the duplicates can make it harder to debug what’s going on with your PATH if you’re trying to understand its contents.

Some ways you could deal with this:

1. If you’re debugging your PATH, open a new terminal to do it in so you get a “fresh” state. This should avoid the duplication.
2. Deduplicate your PATH at the end of your shell’s config (for example in zsh apparently you can do this with typeset -U path)
3. Check that the directory isn’t already in your PATH when adding it (for example in fish I believe you can do this with fish_add_path --path /some/directory)

How to deduplicate your PATH is shell-specific and there isn’t always a built in way to do it so you’ll need to look up how to accomplish it in your shell.

problem 4: losing your history after updating your PATH

Here’s a situation that’s easy to get into in bash or zsh:

1. Run a command (it fails)
2. Update your PATH
3. Run bash to reload your config
4. Press the up arrow a couple of times to rerun the failed command (or open a new terminal)
5. The failed command isn’t in your history! Why not?

This happens because in bash, by default, history is not saved until you exit the shell.

Some options for fixing this:

• Instead of running bash to reload your config, run source ~/.bashrc (or source ~/.zshrc in zsh). This will reload the config inside your current session.
• Configure your shell to continuously save your history instead of only saving the history when the shell exits. (How to do this depends on whether you’re using bash or zsh, the history options in zsh are a bit complicated and I’m not exactly sure what the best way is)

a note on source

When you install cargo (Rust’s installer) for the first time, it gives you these instructions for how to set up your PATH, which don’t mention a specific directory at all.

This is usually done by running one of the following (note the leading DOT):

. "$HOME/.cargo/env"        	# For sh/bash/zsh/ash/dash/pdksh
source "$HOME/.cargo/env.fish"  # For fish

The idea is that you add that line to your shell’s config, and their script automatically sets up your PATH (and potentially other things) for you.

This is pretty common (for example Homebrew suggests you eval brew shellenv), and there are two ways to approach this:

1. Just do what the tool suggests (like adding . "$HOME/.cargo/env" to your shell’s config)
2. Figure out which directories the script they’re telling you to run would add to your PATH, and then add those manually. Here’s how I’d do that:
   • Run . "$HOME/.cargo/env" in my shell (or the fish version if using fish)
   • Run echo "$PATH" | tr ':' '\n' | grep cargo to figure out which directories it added
   • See that it says /Users/bork/.cargo/bin and shorten that to ~/.cargo/bin
   • Add the directory ~/.cargo/bin to PATH (with the directions in this post)

I don’t think there’s anything wrong with doing what the tool suggests (it might be the “best way”!), but personally I usually use the second approach because I prefer knowing exactly what configuration I’m changing.

a note on fish_add_path

fish has a handy function called fish_add_path that you can run to add a directory to your PATH like this:

fish_add_path /some/directory

This is cool (it’s such a simple command!) but I’ve stopped using it for a couple of reasons:

1. Sometimes fish_add_path will update the PATH for every session in the future (with a “universal variable”) and sometimes it will update the PATH just for the current session and it’s hard for me to tell which one it will do. In theory the docs explain this but I could not understand them.
2. If you ever need to remove the directory from your PATH a few weeks or months later because maybe you made a mistake, it’s kind of hard to do (there are instructions in this comments of this github issue though).

that’s all

Hopefully this will help some people. Let me know (on Mastodon or Bluesky) if you there are other major gotchas that have tripped you up when adding a directory to your PATH, or if you have questions about this post!

What’s the most frustrating thing about using the terminal for you?

1600 people answered, and I decided to spend a few days categorizing all the responses. Along the way I learned that classifying qualitative data is not easy but I gave it my best shot. I ended up building a custom tool to make it faster to categorize everything.

As with all of my surveys the methodology isn’t particularly scientific. I just posted the survey to Mastodon and Twitter, ran it for a couple of days, and got answers from whoever happened to see it and felt like responding.

Here are the top categories of frustrations!

I think it’s worth keeping in mind while reading these comments that

• 40% of people answering this survey have been using the terminal for 21+ years
• 95% of people answering the survey have been using the terminal for at least 4 years

These comments aren’t coming from total beginners.

Here are the categories of frustrations! The number in brackets is the number of people with that frustration. I’m mostly writing this up for myself because I’m trying to write a zine about the terminal and I wanted to get a sense for what people are having trouble with.

remembering syntax (115)

People talked about struggles remembering:

• the syntax for CLI tools like awk, jq, sed, etc
• the syntax for redirects
• keyboard shortcuts for tmux, text editing, etc

One example comment:

There are just so many little “trivia” details to remember for full functionality. Even after all these years I’ll sometimes forget where it’s 2 or 1 for stderr, or forget which is which for > and >>.

switching terminals is hard (91)

People talked about struggling with switching systems (for example home/work computer or when SSHing) and running into:

• OS differences in keyboard shortcuts (like Linux vs Mac)
• systems which don’t have their preferred text editor (“no vim” or “only vim”)
• different versions of the same command (like Mac OS grep vs GNU grep)
• no tab completion
• a shell they aren’t used to (“the subtle differences between zsh and bash”)

as well as differences inside the same system like pagers being not consistent with each other (git diff pagers, other pagers).

One example comment:

I got used to fish and vi mode which are not available when I ssh into servers, containers.

color (85)

Lots of problems with color, like:

• programs setting colors that are unreadable with a light background color
• finding a colorscheme they like (and getting it to work consistently across different apps)
• color not working inside several layers of SSH/tmux/etc
• not liking the defaults
• not wanting color at all and struggling to turn it off

This comment felt relatable to me:

Getting my terminal theme configured in a reasonable way between the terminal emulator and fish (I did this years ago and remember it being tedious and fiddly and now feel like I’m locked into my current theme because it works and I dread touching any of that configuration ever again).

keyboard shortcuts (84)

Half of the comments on keyboard shortcuts were about how on Linux/Windows, the keyboard shortcut to copy/paste in the terminal is different from in the rest of the OS.

Some other issues with keyboard shortcuts other than copy/paste:

• using Ctrl-W in a browser-based terminal and closing the window
• the terminal only supports a limited set of keyboard shortcuts (no Ctrl-Shift-, no Super, no Hyper, lots of ctrl- shortcuts aren’t possible like Ctrl-,)
• the OS stopping you from using a terminal keyboard shortcut (like by default Mac OS uses Ctrl+left arrow for something else)
• issues using emacs in the terminal
• backspace not working (2)

other copy and paste issues (75)

Aside from “the keyboard shortcut for copy and paste is different”, there were a lot of OTHER issues with copy and paste, like:

• copying over SSH
• how tmux and the terminal emulator both do copy/paste in different ways
• dealing with many different clipboards (system clipboard, vim clipboard, the “middle click” clipboard on Linux, tmux’s clipboard, etc) and potentially synchronizing them
• random spaces added when copying from the terminal
• pasting multiline commands which automatically get run in a terrifying way
• wanting a way to copy text without using the mouse

discoverability (55)

There were lots of comments about this, which all came down to the same basic complaint – it’s hard to discover useful tools or features! This comment kind of summed it all up:

How difficult it is to learn independently. Most of what I know is an assorted collection of stuff I’ve been told by random people over the years.

steep learning curve (44)

A lot of comments about it generally having a steep learning curve. A couple of example comments:

After 15 years of using it, I’m not much faster than using it than I was 5 or maybe even 10 years ago.

and

That I know I could make my life easier by learning more about the shortcuts and commands and configuring the terminal but I don’t spend the time because it feels overwhelming.

history (42)

Some issues with shell history:

• history not being shared between terminal tabs (16)
• limits that are too short (4)
• history not being restored when terminal tabs are restored
• losing history because the terminal crashed
• not knowing how to search history

One example comment:

It wasted a lot of time until I figured it out and still annoys me that “history” on zsh has such a small buffer; I have to type “history 0” to get any useful length of history.

bad documentation (37)

People talked about:

• documentation being generally opaque
• lack of examples in man pages
• programs which don’t have man pages

Here’s a representative comment:

Finding good examples and docs. Man pages often not enough, have to wade through stack overflow

scrollback (36)

A few issues with scrollback:

• programs printing out too much data making you lose scrollback history
• resizing the terminal messes up the scrollback
• lack of timestamps
• GUI programs that you start in the background printing stuff out that gets in the way of other programs’ outputs

One example comment:

When resizing the terminal (in particular: making it narrower) leads to broken rewrapping of the scrollback content because the commands formatted their output based on the terminal window width.

“it feels outdated” (33)

Lots of comments about how the terminal feels hampered by legacy decisions and how users often end up needing to learn implementation details that feel very esoteric. One example comment:

Most of the legacy cruft, it would be great to have a green field implementation of the CLI interface.

shell scripting (32)

Lots of complaints about POSIX shell scripting. There’s a general feeling that shell scripting is difficult but also that switching to a different less standard scripting language (fish, nushell, etc) brings its own problems.

Shell scripting. My tolerance to ditch a shell script and go to a scripting language is pretty low. It’s just too messy and powerful. Screwing up can be costly so I don’t even bother.

more issues

Some more issues that were mentioned at least 10 times:

• (31) inconsistent command line arguments: is it -h or help or –help?
• (24) keeping dotfiles in sync across different systems
• (23) performance (e.g. “my shell takes too long to start”)
• (20) window management (potentially with some combination of tmux tabs, terminal tabs, and multiple terminal windows. Where did that shell session go?)
• (17) generally feeling scared/uneasy (“The debilitating fear that I’m going to do some mysterious Bad Thing with a command and I will have absolutely no idea how to fix or undo it or even really figure out what happened”)
• (16) terminfo issues (“Having to learn about terminfo if/when I try a new terminal emulator and ssh elsewhere.”)
• (16) lack of image support (sixel etc)
• (15) SSH issues (like having to start over when you lose the SSH connection)
• (15) various tmux/screen issues (for example lack of integration between tmux and the terminal emulator)
• (15) typos & slow typing
• (13) the terminal getting messed up for various reasons (pressing Ctrl-S, cating a binary, etc)
• (12) quoting/escaping in the shell
• (11) various Windows/PowerShell issues

n/a (122)

There were also 122 answers to the effect of “nothing really” or “only that I can’t do EVERYTHING in the terminal”

One example comment:

Think I’ve found work arounds for most/all frustrations

that’s all!

I’m not going to make a lot of commentary on these results, but here are a couple of categories that feel related to me:

• remembering syntax & history (often the thing you need to remember is something you’ve run before!)
• discoverability & the learning curve (the lack of discoverability is definitely a big part of what makes it hard to learn)
• “switching systems is hard” & “it feels outdated” (tools that haven’t really changed in 30 or 40 years have many problems but they do tend to be always there no matter what system you’re on, which is very useful and makes them hard to stop using)

Trying to categorize all these results in a reasonable way really gave me an appreciation for social science researchers’ skills.

There are so many pieces to having a modern terminal experience. I wish it all came out of the box.

My immediate reaction was “oh, getting a modern terminal experience isn’t that hard, you just need to….”, but the more I thought about it, the longer the “you just need to…” list got, and I kept thinking about more and more caveats.

So I thought I would write down some notes about what it means to me personally to have a “modern” terminal experience and what I think can make it hard for people to get there.

what is a “modern terminal experience”?

Here are a few things that are important to me, with which part of the system is responsible for them:

• multiline support for copy and paste: if you paste 3 commands in your shell, it should not immediately run them all! That’s scary! (shell, terminal emulator)
• infinite shell history: if I run a command in my shell, it should be saved forever, not deleted after 500 history entries or whatever. Also I want commands to be saved to the history immediately when I run them, not only when I exit the shell session (shell)
• a useful prompt: I can’t live without having my current directory and current git branch in my prompt (shell)
• 24-bit colour: this is important to me because I find it MUCH easier to theme neovim with 24-bit colour support than in a terminal with only 256 colours (terminal emulator)
• clipboard integration between vim and my operating system so that when I copy in Firefox, I can just press p in vim to paste (text editor, maybe the OS/terminal emulator too)
• good autocomplete: for example commands like git should have command-specific autocomplete (shell)
• having colours in ls (shell config)
• a terminal theme I like: I spend a lot of time in my terminal, I want it to look nice and I want its theme to match my terminal editor’s theme. (terminal emulator, text editor)
• automatic terminal fixing: If a programs prints out some weird escape codes that mess up my terminal, I want that to automatically get reset so that my terminal doesn’t get messed up (shell)
• keybindings: I want Ctrl+left arrow to work (shell or application)
• being able to use the scroll wheel in programs like less: (terminal emulator and applications)

There are a million other terminal conveniences out there and different people value different things, but those are the ones that I would be really unhappy without.

how I achieve a “modern experience”

My basic approach is:

1. use the fish shell. Mostly don’t configure it, except to:
   • set the EDITOR environment variable to my favourite terminal editor
   • alias ls to ls --color=auto
2. use any terminal emulator with 24-bit colour support. In the past I’ve used GNOME Terminal, Terminator, and iTerm, but I’m not picky about this. I don’t really configure it other than to choose a font.
3. use neovim, with a configuration that I’ve been very slowly building over the last 9 years or so (the last time I deleted my vim config and started from scratch was 9 years ago)
4. use the base16 framework to theme everything

A few things that affect my approach:

• I don’t spend a lot of time SSHed into other machines
• I’d rather use the mouse a little than come up with keyboard-based ways to do everything
• I work on a lot of small projects, not one big project

some “out of the box” options for a “modern” experience

What if you want a nice experience, but don’t want to spend a lot of time on configuration? Figuring out how to configure vim in a way that I was satisfied with really did take me like ten years, which is a long time!

My best ideas for how to get a reasonable terminal experience with minimal config are:

• shell: either fish or zsh with oh-my-zsh
• terminal emulator: almost anything with 24-bit colour support, for example all of these are popular:
  • linux: GNOME Terminal, Konsole, Terminator, xfce4-terminal
  • mac: iTerm (Terminal.app doesn’t have 256-colour support)
  • cross-platform: kitty, alacritty, wezterm, or ghostty
• shell config:
  • set the EDITOR environment variable to your favourite terminal text editor
  • maybe alias ls to ls --color=auto
• text editor: this is a tough one, maybe micro or helix? I haven’t used either of them seriously but they both seem like very cool projects and I think it’s amazing that you can just use all the usual GUI editor commands (Ctrl-C to copy, Ctrl-V to paste, Ctrl-A to select all) in micro and they do what you’d expect. I would probably try switching to helix except that retraining my vim muscle memory seems way too hard. Also helix doesn’t have a GUI or plugin system yet.

Personally I wouldn’t use xterm, rxvt, or Terminal.app as a terminal emulator, because I’ve found in the past that they’re missing core features (like 24-bit colour in Terminal.app’s case) that make the terminal harder to use for me.

I don’t want to pretend that getting a “modern” terminal experience is easier than it is though – I think there are two issues that make it hard. Let’s talk about them!

issue 1 with getting to a “modern” experience: the shell

bash and zsh are by far the two most popular shells, and neither of them provide a default experience that I would be happy using out of the box, for example:

• you need to customize your prompt
• they don’t come with git completions by default, you have to set them up
• by default, bash only stores 500 (!) lines of history and (at least on Mac OS) zsh is only configured to store 2000 lines, which is still not a lot
• I find bash’s tab completion very frustrating, if there’s more than one match then you can’t tab through them

And even though I love fish, the fact that it isn’t POSIX does make it hard for a lot of folks to make the switch.

Of course it’s totally possible to learn how to customize your prompt in bash or whatever, and it doesn’t even need to be that complicated (in bash I’d probably start with something like export PS1='[\u@\h \W$(__git_ps1 " (%s)")]\$ ', or maybe use starship). But each of these “not complicated” things really does add up and it’s especially tough if you need to keep your config in sync across several systems.

An extremely popular solution to getting a “modern” shell experience is oh-my-zsh. It seems like a great project and I know a lot of people use it very happily, but I’ve struggled with configuration systems like that in the past – it looks like right now the base oh-my-zsh adds about 3000 lines of config, and often I find that having an extra configuration system makes it harder to debug what’s happening when things go wrong. I personally have a tendency to use the system to add a lot of extra plugins, make my system slow, get frustrated that it’s slow, and then delete it completely and write a new config from scratch.

issue 2 with getting to a “modern” experience: the text editor

In the terminal survey I ran recently, the most popular terminal text editors by far were vim, emacs, and nano.

I think the main options for terminal text editors are:

• use vim or emacs and configure it to your liking, you can probably have any feature you want if you put in the work
• use nano and accept that you’re going to have a pretty limited experience (for example I don’t think you can select text with the mouse and then “cut” it in nano)
• use micro or helix which seem to offer a pretty good out-of-the-box experience, potentially occasionally run into issues with using a less mainstream text editor
• just avoid using a terminal text editor as much as possible, maybe use VSCode, use VSCode’s terminal for all your terminal needs, and mostly never edit files in the terminal. Or I know a lot of people use code as their EDITOR in the terminal.

issue 3: individual applications

The last issue is that sometimes individual programs that I use are kind of annoying. For example on my Mac OS machine, /usr/bin/sqlite3 doesn’t support the Ctrl+Left Arrow keyboard shortcut. Fixing this to get a reasonable terminal experience in SQLite was a little complicated, I had to:

• realize why this is happening (Mac OS won’t ship GNU tools, and “Ctrl-Left arrow” support comes from GNU readline)
• find a workaround (install sqlite from homebrew, which does have readline support)
• adjust my environment (put Homebrew’s sqlite3 in my PATH)

I find that debugging application-specific issues like this is really not easy and often it doesn’t feel “worth it” – often I’ll end up just dealing with various minor inconveniences because I don’t want to spend hours investigating them. The only reason I was even able to figure this one out at all is that I’ve been spending a huge amount of time thinking about the terminal recently.

A big part of having a “modern” experience using terminal programs is just using newer terminal programs, for example I can’t be bothered to learn a keyboard shortcut to sort the columns in top, but in htop I can just click on a column heading with my mouse to sort it. So I use htop instead! But discovering new more “modern” command line tools isn’t easy (though I made a list here), finding ones that I actually like using in practice takes time, and if you’re SSHed into another machine, they won’t always be there.

everything affects everything else

Something I find tricky about configuring my terminal to make everything “nice” is that changing one seemingly small thing about my workflow can really affect everything else. For example right now I don’t use tmux. But if I needed to use tmux again (for example because I was doing a lot of work SSHed into another machine), I’d need to think about a few things, like:

• if I wanted tmux’s copy to synchronize with my system clipboard over SSH, I’d need to make sure that my terminal emulator has OSC 52 support
• if I wanted to use iTerm’s tmux integration (which makes tmux tabs into iTerm tabs), I’d need to change how I configure colours – right now I set them with a shell script that I run when my shell starts, but that means the colours get lost when restoring a tmux session.

and probably more things I haven’t thought of. “Using tmux means that I have to change how I manage my colours” sounds unlikely, but that really did happen to me and I decided “well, I don’t want to change how I manage colours right now, so I guess I’m not using that feature!”.

It’s also hard to remember which features I’m relying on – for example maybe my current terminal does have OSC 52 support and because copying from tmux over SSH has always Just Worked I don’t even realize that that’s something I need, and then it mysteriously stops working when I switch terminals.

change things slowly

Personally even though I think my setup is not that complicated, it’s taken me 20 years to get to this point! Because terminal config changes are so likely to have unexpected and hard-to-understand consequences, I’ve found that if I change a lot of terminal configuration all at once it makes it much harder to understand what went wrong if there’s a problem, which can be really disorienting.

So I usually prefer to make pretty small changes, and accept that changes can might take me a REALLY long time to get used to. For example I switched from using ls to eza a year or two ago and while I like it (because eza -l prints human-readable file sizes by default) I’m still not quite sure about it. But also sometimes it’s worth it to make a big change, like I made the switch to fish (from bash) 10 years ago and I’m very happy I did.

getting a “modern” terminal is not that easy

Trying to explain how “easy” it is to configure your terminal really just made me think that it’s kind of hard and that I still sometimes get confused.

I’ve found that there’s never one perfect way to configure things in the terminal that will be compatible with every single other thing. I just need to try stuff, figure out some kind of locally stable state that works for me, and accept that if I start using a new tool it might disrupt the system and I might need to rethink things.

1. Your operating system’s job
2. Your shell’s job
3. Your terminal emulator’s job
4. The job of whatever program you happen to be running (like top or vim or cat)

The first three (your operating system, shell, and terminal emulator) are all kind of known quantities – if you’re using bash in GNOME Terminal on Linux, you can more or less reason about how how all of those things interact, and some of their behaviour is standardized by POSIX.

But the fourth one (“whatever program you happen to be running”) feels like it could do ANYTHING. How are you supposed to know how a program is going to behave?

This post is kind of long so here’s a quick table of contents:

• programs behave surprisingly consistently
• these are meant to be descriptive, not prescriptive
• it’s not always obvious which “rules” are the program’s responsibility to implement
• rule 1: noninteractive programs should quit when you press Ctrl-C
• rule 2: TUIs should quit when you press q
• rule 3: REPLs should quit when you press Ctrl-D on an empty line
• rule 4: don’t use more than 16 colours
• rule 5: vaguely support readline keybindings
• rule 5.1: Ctrl-W should delete the last word
• rule 6: disable colours when writing to a pipe
• rule 7: - means stdin/stdout
• these “rules” take a long time to learn

programs behave surprisingly consistently

As far as I know, there are no real standards for how programs in the terminal should behave – the closest things I know of are:

• POSIX, which mostly dictates how your terminal emulator / OS / shell should work together. I think it does specify a few things about how core utilities like cp should work but AFAIK it doesn’t have anything to say about how for example htop should behave.
• these command line interface guidelines

But even though there are no standards, in my experience programs in the terminal behave in a pretty consistent way. So I wanted to write down a list of “rules” that in my experience programs mostly follow.

these are meant to be descriptive, not prescriptive

My goal here isn’t to convince authors of terminal programs that they should follow any of these rules. There are lots of exceptions to these and often there’s a good reason for those exceptions.

But it’s very useful for me to know what behaviour to expect from a random new terminal program that I’m using. Instead of “uh, programs could do literally anything”, it’s “ok, here are the basic rules I expect, and then I can keep a short mental list of exceptions”.

So I’m just writing down what I’ve observed about how programs behave in my 20 years of using the terminal, why I think they behave that way, and some examples of cases where that rule is “broken”.

it’s not always obvious which “rules” are the program’s responsibility to implement

There are a bunch of common conventions that I think are pretty clearly the program’s responsibility to implement, like:

• config files should go in ~/.BLAHrc or ~/.config/BLAH/FILE or /etc/BLAH/ or something
• --help should print help text
• programs should print “regular” output to stdout and errors to stderr

But in this post I’m going to focus on things that it’s not 100% obvious are the program’s responsibility. For example it feels to me like a “law of nature” that pressing Ctrl-D should quit a REPL, but programs often need to explicitly implement support for it – even though cat doesn’t need to implement Ctrl-D support, ipython does. (more about that in “rule 3” below)

Understanding which things are the program’s responsibility makes it much less surprising when different programs’ implementations are slightly different.

rule 1: noninteractive programs should quit when you press Ctrl-C

The main reason for this rule is that noninteractive programs will quit by default on Ctrl-C if they don’t set up a SIGINT signal handler, so this is kind of a “you should act like the default” rule.

Something that trips a lot of people up is that this doesn’t apply to interactive programs like python3 or bc or less. This is because in an interactive program, Ctrl-C has a different job – if the program is running an operation (like for example a search in less or some Python code in python3), then Ctrl-C will interrupt that operation but not stop the program.

As an example of how this works in an interactive program: here’s the code in prompt-toolkit (the library that iPython uses for handling input) that aborts a search when you press Ctrl-C.

rule 2: TUIs should quit when you press q

TUI programs (like less or htop) will usually quit when you press q.

This rule doesn’t apply to any program where pressing q to quit wouldn’t make sense, like tmux or text editors.

rule 3: REPLs should quit when you press Ctrl-D on an empty line

REPLs (like python3 or ed) will usually quit when you press Ctrl-D on an empty line. This rule is similar to the Ctrl-C rule – the reason for this is that by default if you’re running a program (like cat) in “cooked mode”, then the operating system will return an EOF when you press Ctrl-D on an empty line.

Most of the REPLs I use (sqlite3, python3, fish, bash, etc) don’t actually use cooked mode, but they all implement this keyboard shortcut anyway to mimic the default behaviour.

For example, here’s the code in prompt-toolkit that quits when you press Ctrl-D, and here’s the same code in readline.

I actually thought that this one was a “Law of Terminal Physics” until very recently because I’ve basically never seen it broken, but you can see that it’s just something that each individual input library has to implement in the links above.

Someone pointed out that the Erlang REPL does not quit when you press Ctrl-D, so I guess not every REPL follows this “rule”.

rule 4: don’t use more than 16 colours

Terminal programs rarely use colours other than the base 16 ANSI colours. This is because if you specify colours with a hex code, it’s very likely to clash with some users’ background colour. For example if I print out some text as #EEEEEE, it would be almost invisible on a white background, though it would look fine on a dark background.

But if you stick to the default 16 base colours, you have a much better chance that the user has configured those colours in their terminal emulator so that they work reasonably well with their background color. Another reason to stick to the default base 16 colours is that it makes less assumptions about what colours the terminal emulator supports.

The only programs I usually see breaking this “rule” are text editors, for example Helix by default will use a purple background which is not a default ANSI colour. It seems fine for Helix to break this rule since Helix isn’t a “core” program and I assume any Helix user who doesn’t like that colorscheme will just change the theme.

rule 5: vaguely support readline keybindings

Almost every program I use supports readline keybindings if it would make sense to do so. For example, here are a bunch of different programs and a link to where they define Ctrl-E to go to the end of the line:

• ipython (Ctrl-E defined here)
• atuin (Ctrl-E defined here)
• fzf (Ctrl-E defined here)
• zsh (Ctrl-E defined here)
• fish (Ctrl-E defined here)
• tmux’s command prompt (Ctrl-E defined here)

None of those programs actually uses readline directly, they just sort of mimic emacs/readline keybindings. They don’t always mimic them exactly: for example atuin seems to use Ctrl-A as a prefix, so Ctrl-A doesn’t go to the beginning of the line.

Also all of these programs seem to implement their own internal cut and paste buffers so you can delete a line with Ctrl-U and then paste it with Ctrl-Y.

The exceptions to this are:

• some programs (like git, cat, and nc) don’t have any line editing support at all (except for backspace, Ctrl-W, and Ctrl-U)
• as usual text editors are an exception, every text editor has its own approach to editing text

I wrote more about this “what keybindings does a program support?” question in entering text in the terminal is complicated.

rule 5.1: Ctrl-W should delete the last word

I’ve never seen a program (other than a text editor) where Ctrl-W doesn’t delete the last word. This is similar to the Ctrl-C rule – by default if a program is in “cooked mode”, the OS will delete the last word if you press Ctrl-W, and delete the whole line if you press Ctrl-U. So usually programs will imitate that behaviour.

I can’t think of any exceptions to this other than text editors but if there are I’d love to hear about them!

rule 6: disable colours when writing to a pipe

Most programs will disable colours when writing to a pipe. For example:

• rg blah will highlight all occurrences of blah in the output, but if the output is to a pipe or a file, it’ll turn off the highlighting.
• ls --color=auto will use colour when writing to a terminal, but not when writing to a pipe

Both of those programs will also format their output differently when writing to the terminal: ls will organize files into columns, and ripgrep will group matches with headings.

If you want to force the program to use colour (for example because you want to look at the colour), you can use unbuffer to force the program’s output to be a tty like this:

unbuffer rg blah |  less -R

I’m sure that there are some programs that “break” this rule but I can’t think of any examples right now. Some programs have an --color flag that you can use to force colour to be on, in the example above you could also do rg --color=always | less -R.

rule 7: - means stdin/stdout

Usually if you pass - to a program instead of a filename, it’ll read from stdin or write to stdout (whichever is appropriate). For example, if you want to format the Python code that’s on your clipboard with black and then copy it, you could run:

pbpaste | black - | pbcopy

(pbpaste is a Mac program, you can do something similar on Linux with xclip)

My impression is that most programs implement this if it would make sense and I can’t think of any exceptions right now, but I’m sure there are many exceptions.

these “rules” take a long time to learn

These rules took me a long time for me to learn because I had to:

1. learn that the rule applied anywhere at all ("Ctrl-C will exit programs")
2. notice some exceptions (“okay, Ctrl-C will exit find but not less”)
3. subconsciously figure out what the pattern is ("Ctrl-C will generally quit noninteractive programs, but in interactive programs it might interrupt the current operation instead of quitting the program")
4. eventually maybe formulate it into an explicit rule that I know

A lot of my understanding of the terminal is honestly still in the “subconscious pattern recognition” stage. The only reason I’ve been taking the time to make things explicit at all is because I’ve been trying to explain how it works to others. Hopefully writing down these “rules” explicitly will make learning some of this stuff a little bit faster for others.

tail -f /some/log/file | grep thing1 | grep thing2

If log lines are being added to the file relatively slowly, the result I’d see is… nothing! It doesn’t matter if there were matches in the log file or not, there just wouldn’t be any output.

I internalized this as “uh, I guess pipes just get stuck sometimes and don’t show me the output, that’s weird”, and I’d handle it by just running grep thing1 /some/log/file | grep thing2 instead, which would work.

So as I’ve been doing a terminal deep dive over the last few months I was really excited to finally learn exactly why this happens.

why this happens: buffering

The reason why “pipes get stuck” sometimes is that it’s VERY common for programs to buffer their output before writing it to a pipe or file. So the pipe is working fine, the problem is that the program never even wrote the data to the pipe!

This is for performance reasons: writing all output immediately as soon as you can uses more system calls, so it’s more efficient to save up data until you have 8KB or so of data to write (or until the program exits) and THEN write it to the pipe.

In this example:

tail -f /some/log/file | grep thing1 | grep thing2

the problem is that grep thing1 is saving up all of its matches until it has 8KB of data to write, which might literally never happen.

programs don’t buffer when writing to a terminal

Part of why I found this so disorienting is that tail -f file | grep thing will work totally fine, but then when you add the second grep, it stops working!! The reason for this is that the way grep handles buffering depends on whether it’s writing to a terminal or not.

Here’s how grep (and many other programs) decides to buffer its output:

• Check if stdout is a terminal or not using the isatty function
  • If it’s a terminal, use line buffering (print every line immediately as soon as you have it)
  • Otherwise, use “block buffering” – only print data if you have at least 8KB or so of data to print

So if grep is writing directly to your terminal then you’ll see the line as soon as it’s printed, but if it’s writing to a pipe, you won’t.

Of course the buffer size isn’t always 8KB for every program, it depends on the implementation. For grep the buffering is handled by libc, and libc’s buffer size is defined in the BUFSIZ variable. Here’s where that’s defined in glibc.

(as an aside: “programs do not use 8KB output buffers when writing to a terminal” isn’t, like, a law of terminal physics, a program COULD use an 8KB buffer when writing output to a terminal if it wanted, it would just be extremely weird if it did that, I can’t think of any program that behaves that way)

commands that buffer & commands that don’t

One annoying thing about this buffering behaviour is that you kind of need to remember which commands buffer their output when writing to a pipe.

Some commands that don’t buffer their output:

• tail
• cat
• tee

I think almost everything else will buffer output, especially if it’s a command where you’re likely to be using it for batch processing. Here’s a list of some common commands that buffer their output when writing to a pipe, along with the flag that disables block buffering.

• grep (--line-buffered)
• sed (-u)
• awk (there’s a fflush() function)
• tcpdump (-l)
• jq (-u)
• tr (-u)
• cut (can’t disable buffering)

Those are all the ones I can think of, lots of unix commands (like sort) may or may not buffer their output but it doesn’t matter because sort can’t do anything until it finishes receiving input anyway.

Also I did my best to test both the Mac OS and GNU versions of these but there are a lot of variations and I might have made some mistakes.

programming languages where the default “print” statement buffers

Also, here are a few programming language where the default print statement will buffer output when writing to a pipe, and some ways to disable buffering if you want:

• C (disable with setvbuf)
• Python (disable with python -u, or PYTHONUNBUFFERED=1, or sys.stdout.reconfigure(line_buffering=False), or print(x, flush=True))
• Ruby (disable with STDOUT.sync = true)
• Perl (disable with $| = 1)

I assume that these languages are designed this way so that the default print function will be fast when you’re doing batch processing.

Also whether output is buffered or not might depend on how you print, for example in C++ cout << "hello\n" buffers when writing to a pipe but cout << "hello" << endl will flush its output.

when you press Ctrl-C on a pipe, the contents of the buffer are lost

Let’s say you’re running this command as a hacky way to watch for DNS requests to example.com, and you forgot to pass -l to tcpdump:

sudo tcpdump -ni any port 53 | grep example.com

When you press Ctrl-C, what happens? In a magical perfect world, what I would want to happen is for tcpdump to flush its buffer, grep would search for example.com, and I would see all the output I missed.

But in the real world, what happens is that all the programs get killed and the output in tcpdump’s buffer is lost.

I think this problem is probably unavoidable – I spent a little time with strace to see how this works and grep receives the SIGINT before tcpdump anyway so even if tcpdump tried to flush its buffer grep would already be dead.

redirecting to a file also buffers

It’s not just pipes, this will also buffer:

sudo tcpdump -ni any port 53 > output.txt

Redirecting to a file doesn’t have the same “Ctrl-C will totally destroy the contents of the buffer” problem though – in my experience it usually behaves more like you’d want, where the contents of the buffer get written to the file before the program exits. I’m not 100% sure whether this is something you can always rely on or not.

a bunch of potential ways to avoid buffering

Okay, let’s talk solutions. Let’s say you’ve run this command:

tail -f /some/log/file | grep thing1 | grep thing2

I asked people on Mastodon how they would solve this in practice and there were 5 basic approaches. Here they are:

solution 1: run a program that finishes quickly

Historically my solution to this has been to just avoid the “command writing to pipe slowly” situation completely and instead run a program that will finish quickly like this:

cat /some/log/file | grep thing1 | grep thing2 | tail

This doesn’t do the same thing as the original command but it does mean that you get to avoid thinking about these weird buffering issues.

(you could also do grep thing1 /some/log/file but I often prefer to use an “unnecessary” cat)

solution 2: remember the “line buffer” flag to grep

You could remember that grep has a flag to avoid buffering and pass it like this:

tail -f /some/log/file | grep --line-buffered thing1 | grep thing2

solution 3: use awk

Some people said that if they’re specifically dealing with a multiple greps situation, they’ll rewrite it to use a single awk instead, like this:

tail -f /some/log/file |  awk '/thing1/ && /thing2/'

Or you would write a more complicated grep, like this:

tail -f /some/log/file |  grep -E 'thing1.*thing2'

(awk also buffers, so for this to work you’ll want awk to be the last command in the pipeline)

solution 4: use stdbuf

stdbuf uses LD_PRELOAD to turn off libc’s buffering, and you can use it to turn off output buffering like this:

tail -f /some/log/file | stdbuf -o0 grep thing1 | grep thing2

Like any LD_PRELOAD solution it’s a bit unreliable – it doesn’t work on static binaries, I think won’t work if the program isn’t using libc’s buffering, and doesn’t always work on Mac OS. Harry Marr has a really nice How stdbuf works post.

solution 5: use unbuffer

unbuffer program will force the program’s output to be a TTY, which means that it’ll behave the way it normally would on a TTY (less buffering, colour output, etc). You could use it in this example like this:

tail -f /some/log/file | unbuffer grep thing1 | grep thing2

Unlike stdbuf it will always work, though it might have unwanted side effects, for example grep thing1’s will also colour matches.

If you want to install unbuffer, it’s in the expect package.

that’s all the solutions I know about!

It’s a bit hard for me to say which one is “best”, I think personally I’m mostly likely to use unbuffer because I know it’s always going to work.

If I learn about more solutions I’ll try to add them to this post.

I’m not really sure how often this comes up

I think it’s not very common for me to have a program that slowly trickles data into a pipe like this, normally if I’m using a pipe a bunch of data gets written very quickly, processed by everything in the pipeline, and then everything exits. The only examples I can come up with right now are:

• tcpdump
• tail -f
• watching log files in a different way like with kubectl logs
• the output of a slow computation

what if there were an environment variable to disable buffering?

I think it would be cool if there were a standard environment variable to turn off buffering, like PYTHONUNBUFFERED in Python. I got this idea from a couple of blog posts by Mark Dominus in 2018. Maybe NO_BUFFER like NO_COLOR?

The design seems tricky to get right; Mark points out that NETBSD has environment variables called STDBUF, STDBUF1, etc which gives you a ton of control over buffering but I imagine most developers don’t want to implement many different environment variables to handle a relatively minor edge case.

I’m also curious about whether there are any programs that just automatically flush their output buffers after some period of time (like 1 second). It feels like it would be nice in theory but I can’t think of any program that does that so I imagine there are some downsides.

stuff I left out

Some things I didn’t talk about in this post since these posts have been getting pretty long recently and seriously does anyone REALLY want to read 3000 words about buffering?

• the difference between line buffering and having totally unbuffered output
• how buffering to stderr is different from buffering to stdout
• this post is only about buffering that happens inside the program, your operating system’s TTY driver also does a little bit of buffering sometimes
• other reasons you might need to flush your output other than “you’re writing to a pipe”

Luckily at this point I’ve mostly learned how to navigate this situation and either successfully use the library or decide it’s too difficult and switch to a different library, so here’s the guide I wish I had to importing Javascript libraries years ago.

I’m only going to talk about using Javacript libraries on the frontend, and only about how to use them in a no-build-system setup.

In this post I’m going to talk about:

1. the three main types of Javascript files a library might provide (ES Modules, the “classic” global variable kind, and CommonJS)
2. how to figure out which types of files a Javascript library includes in its build
3. ways to import each type of file in your code

the three kinds of Javascript files

There are 3 basic types of Javascript files a library can provide:

1. the “classic” type of file that defines a global variable. This is the kind of file that you can just <script src> and it’ll Just Work. Great if you can get it but not always available
2. an ES module (which may or may not depend on other files, we’ll get to that)
3. a “CommonJS” module. This is for Node, you can’t use it in a browser at all without using a build system.

I’m not sure if there’s a better name for the “classic” type but I’m just going to call it “classic”. Also there’s a type called “AMD” but I’m not sure how relevant it is in 2024.

Now that we know the 3 types of files, let’s talk about how to figure out which of these the library actually provides!

where to find the files: the NPM build

Every Javascript library has a build which it uploads to NPM. You might be thinking (like I did originally) – Julia! The whole POINT is that we’re not using Node to build our library! Why are we talking about NPM?

But if you’re using a link from a CDN like https://cdnjs.cloudflare.com/ajax/libs/Chart.js/4.4.1/chart.umd.min.js, you’re still using the NPM build! All the files on the CDNs originally come from NPM.

Because of this, I sometimes like to npm install the library even if I’m not planning to use Node to build my library at all – I’ll just create a new temp folder, npm install there, and then delete it when I’m done. I like being able to poke around in the files in the NPM build on my filesystem, because then I can be 100% sure that I’m seeing everything that the library is making available in its build and that the CDN isn’t hiding something from me.

So let’s npm install a few libraries and try to figure out what types of Javascript files they provide in their builds!

example library 1: chart.js

First let’s look inside Chart.js, a plotting library.

$ cd /tmp/whatever
$ npm install chart.js
$ cd node_modules/chart.js/dist
$ ls *.*js
chart.cjs  chart.js  chart.umd.js  helpers.cjs  helpers.js

This library seems to have 3 basic options:

option 1: chart.cjs. The .cjs suffix tells me that this is a CommonJS file, for using in Node. This means it’s impossible to use it directly in the browser without some kind of build step.

option 2:chart.js. The .js suffix by itself doesn’t tell us what kind of file it is, but if I open it up, I see import '@kurkle/color'; which is an immediate sign that this is an ES module – the import ... syntax is ES module syntax.

option 3: chart.umd.js. “UMD” stands for “Universal Module Definition”, which I think means that you can use this file either with a basic <script src>, CommonJS, or some third thing called AMD that I don’t understand.

how to use a UMD file

When I was using Chart.js I picked Option 3. I just needed to add this to my code:

<script src="./chart.umd.js"> </script>

and then I could use the library with the global Chart environment variable. Couldn’t be easier. I just copied chart.umd.js into my Git repository so that I didn’t have to worry about using NPM or the CDNs going down or anything.

the build files aren’t always in the dist directory

A lot of libraries will put their build in the dist directory, but not always! The build files’ location is specified in the library’s package.json.

For example here’s an excerpt from Chart.js’s package.json.

  "jsdelivr": "./dist/chart.umd.js",
  "unpkg": "./dist/chart.umd.js",
  "main": "./dist/chart.cjs",
  "module": "./dist/chart.js",

I think this is saying that if you want to use an ES Module (module) you should use dist/chart.js, but the jsDelivr and unpkg CDNs should use ./dist/chart.umd.js. I guess main is for Node.

chart.js’s package.json also says "type": "module", which according to this documentation tells Node to treat files as ES modules by default. I think it doesn’t tell us specifically which files are ES modules and which ones aren’t but it does tell us that something in there is an ES module.

example library 2: @atcute/oauth-browser-client

@atcute/oauth-browser-client is a library for logging into Bluesky with OAuth in the browser.

Let’s see what kinds of Javascript files it provides in its build!

$ npm install @atcute/oauth-browser-client
$ cd node_modules/@atcute/oauth-browser-client/dist
$ ls *js
constants.js  dpop.js  environment.js  errors.js  index.js  resolvers.js

It seems like the only plausible root file in here is index.js, which looks something like this:

export { configureOAuth } from './environment.js';
export * from './errors.js';
export * from './resolvers.js';

This export syntax means it’s an ES module. That means we can use it in the browser without a build step! Let’s see how to do that.

how to use an ES module with importmaps

Using an ES module isn’t an easy as just adding a <script src="whatever.js">. Instead, if the ES module has dependencies (like @atcute/oauth-browser-client does) the steps are:

1. Set up an import map in your HTML
2. Put import statements like import { configureOAuth } from '@atcute/oauth-browser-client'; in your JS code
3. Include your JS code in your HTML like this: <script type="module" src="YOURSCRIPT.js"></script>

The reason we need an import map instead of just doing something like import { BrowserOAuthClient } from "./oauth-client-browser.js" is that internally the module has more import statements like import {something} from @atcute/client, and we need to tell the browser where to get the code for @atcute/client and all of its other dependencies.

Here’s what the importmap I used looks like for @atcute/oauth-browser-client:

<script type="importmap">
{
  "imports": {
    "nanoid": "./node_modules/nanoid/bin/dist/index.js",
    "nanoid/non-secure": "./node_modules/nanoid/non-secure/index.js",
    "nanoid/url-alphabet": "./node_modules/nanoid/url-alphabet/dist/index.js",
    "@atcute/oauth-browser-client": "./node_modules/@atcute/oauth-browser-client/dist/index.js",
    "@atcute/client": "./node_modules/@atcute/client/dist/index.js",
    "@atcute/client/utils/did": "./node_modules/@atcute/client/dist/utils/did.js"
  }
}
</script>

Getting these import maps to work is pretty fiddly, I feel like there must be a tool to generate them automatically but I haven’t found one yet. It’s definitely possible to write a script that automatically generates the importmaps using esbuild’s metafile but I haven’t done that and maybe there’s a better way.

I decided to set up importmaps yesterday to get github.com/jvns/bsky-oauth-example to work, so there’s some example code in that repo.

Also someone pointed me to Simon Willison’s download-esm, which will download an ES module and rewrite the imports to point to the JS files directly so that you don’t need importmaps. I haven’t tried it yet but it seems like a great idea.

problems with importmaps: too many files

I did run into some problems with using importmaps in the browser though – it needed to download dozens of Javascript files to load my site, and my webserver in development couldn’t keep up for some reason. I kept seeing files fail to load randomly and then had to reload the page and hope that they would succeed this time.

It wasn’t an issue anymore when I deployed my site to production, so I guess it was a problem with my local dev environment.

Also one slightly annoying thing about ES modules in general is that you need to be running a webserver to use them, I’m sure this is for a good reason but it’s easier when you can just open your index.html file without starting a webserver.

Because of the “too many files” thing I think actually using ES modules with importmaps in this way isn’t actually that appealing to me, but it’s good to know it’s possible.

how to use an ES module without importmaps

If the ES module doesn’t have dependencies then it’s even easier – you don’t need the importmaps! You can just:

• put <script type="module" src="YOURCODE.js"></script> in your HTML. The type="module" is important.
• put import {whatever} from "https://example.com/whatever.js" in YOURCODE.js

alternative: use esbuild

If you don’t want to use importmaps, you can also use a build system like esbuild. I talked about how to do that in Some notes on using esbuild, but this blog post is about ways to avoid build systems completely so I’m not going to talk about that option here. I do still like esbuild though and I think it’s a good option in this case.

what’s the browser support for importmaps?

CanIUse says that importmaps are in “Baseline 2023: newly available across major browsers” so my sense is that in 2024 that’s still maybe a little bit too new? I think I would use importmaps for some fun experimental code that I only wanted like myself and 12 people to use, but if I wanted my code to be more widely usable I’d use esbuild instead.

example library 3: @atproto/oauth-client-browser

Let’s look at one final example library! This is a different Bluesky auth library than @atcute/oauth-browser-client.

$ npm install @atproto/oauth-client-browser
$ cd node_modules/@atproto/oauth-client-browser/dist
$ ls *js
browser-oauth-client.js  browser-oauth-database.js  browser-runtime-implementation.js  errors.js  index.js  indexed-db-store.js  util.js

Again, it seems like only real candidate file here is index.js. But this is a different situation from the previous example library! Let’s take a look at index.js:

There’s a bunch of stuff like this in index.js:

__exportStar(require("@atproto/oauth-client"), exports);
__exportStar(require("./browser-oauth-client.js"), exports);
__exportStar(require("./errors.js"), exports);
var util_js_1 = require("./util.js");

This require() syntax is CommonJS syntax, which means that we can’t use this file in the browser at all, we need to use some kind of build step, and ESBuild won’t work either.

Also in this library’s package.json it says "type": "commonjs" which is another way to tell it’s CommonJS.

how to use a CommonJS module with esm.sh

Originally I thought it was impossible to use CommonJS modules without learning a build system, but then someone Bluesky told me about esm.sh! It’s a CDN that will translate anything into an ES Module. skypack.dev does something similar, I’m not sure what the difference is but one person mentioned that if one doesn’t work sometimes they’ll try the other one.

For @atproto/oauth-client-browser using it seems pretty simple, I just need to put this in my HTML:

<script type="module" src="script.js"> </script>

and then put this in script.js.

import { BrowserOAuthClient } from "https://esm.sh/@atproto/[email protected]"

It seems to Just Work, which is cool! Of course this is still sort of using a build system – it’s just that esm.sh is running the build instead of me. My main concerns with this approach are:

• I don’t really trust CDNs to keep working forever – usually I like to copy dependencies into my repository so that they don’t go away for some reason in the future.
• I’ve heard of some issues with CDNs having security compromises which scares me.
• I don’t really understand what esm.sh is doing.

esbuild can also convert CommonJS modules into ES modules

I also learned that you can also use esbuild to convert a CommonJS module into an ES module, though there are some limitations – the import { BrowserOAuthClient } from syntax doesn’t work. Here’s a github issue about that.

I think the esbuild approach is probably more appealing to me than the esm.sh approach because it’s a tool that I already have on my computer so I trust it more. I haven’t experimented with this much yet though.

summary of the three types of files

Here’s a summary of the three types of JS files you might encounter, options for how to use them, and how to identify them.

Unhelpfully a .js or .min.js file extension could be any of these 3 options, so if the file is something.js you need to do more detective work to figure out what you’re dealing with.

1. “classic” JS files
   • How to use it:: <script src="whatever.js"></script>
   • Ways to identify it:
     • The website has a big friendly banner in its setup instructions saying “Use this with a CDN!” or something
     • A .umd.js extension
     • Just try to put it in a <script src=... tag and see if it works
2. ES Modules
   • Ways to use it:
     • If there are no dependencies, just import {whatever} from "./my-module.js" directly in your code
     • If there are dependencies, create an importmap and import {whatever} from "my-module"
       • or use download-esm to remove the need for an importmap
     • Use esbuild or any ES Module bundler
   • Ways to identify it:
     • Look for an import or export statement. (not module.exports = ..., that’s CommonJS)
     • An .mjs extension
     • maybe "type": "module" in package.json (though it’s not clear to me which file exactly this refers to)
3. CommonJS Modules
   • Ways to use it:
     • Use https://esm.sh to convert it into an ES module, like https://esm.sh/@atproto/[email protected]
     • Use a build somehow (??)
   • Ways to identify it:
     • Look for require() or module.exports = ... in the code
     • A .cjs extension
     • maybe "type": "commonjs" in package.json (though it’s not clear to me which file exactly this refers to)

it’s really nice to have ES modules standardized

The main difference between CommonJS modules and ES modules from my perspective is that ES modules are actually a standard. This makes me feel a lot more confident using them, because browsers commit to backwards compatibility for web standards forever – if I write some code using ES modules today, I can feel sure that it’ll still work the same way in 15 years.

It also makes me feel better about using tooling like esbuild because even if the esbuild project dies, because it’s implementing a standard it feels likely that there will be another similar tool in the future that I can replace it with.

the JS community has built a lot of very cool tools

A lot of the time when I talk about this stuff I get responses like “I hate javascript!!! it’s the worst!!!”. But my experience is that there are a lot of great tools for Javascript (I just learned about https://esm.sh yesterday which seems great! I love esbuild!), and that if I take the time to learn how things works I can take advantage of some of those tools and make my life a lot easier.

So the goal of this post is definitely not to complain about Javascript, it’s to understand the landscape so I can use the tooling in a way that feels good to me.

questions I still have

Here are some questions I still have, I’ll add the answers into the post if I learn the answer.

• Is there a tool that automatically generates importmaps for an ES Module that I have set up locally? (apparently yes: jspm)
• How can I convert a CommonJS module into an ES module on my computer, the way https://esm.sh does? (apparently esbuild can sort of do this, though named exports don’t work)
• When people normally build CommonJS modules into regular JS code, what’s code is doing that? Obviously there are tools like webpack, rollup, esbuild, etc, but do those tools all implement their own JS parsers/static analysis? How many JS parsers are there out there?
• Is there any way to bundle an ES module into a single file (like atcute-client.js), but so that in the browser I can still import multiple different paths from that file (like both @atcute/client/lexicons and @atcute/client)?

all the tools

Here’s a list of every tool we talked about in this post:

• Simon Willison’s download-esm which will download an ES module and convert the imports to point at JS files so you don’t need an importmap
• https://esm.sh/ and skypack.dev
• esbuild
• JSPM can generate importmaps

Writing this post has made me think that even though I usually don’t want to have a build that I run every time I update the project, I might be willing to have a build step (using download-esm or something) that I run only once when setting up the project and never run again except maybe if I’m updating my dependency versions.

that’s all!

Thanks to Marco Rogers who taught me a lot of the things in this post. I’ve probably made some mistakes in this post and I’d love to know what they are – let me know on Bluesky or Mastodon!

the goal: save interesting tools & facts I posted on social media

One kind of thing I like to post on Mastodon/Bluesky is “hey, here’s a cool thing”, like the great SQLite repl litecli, or the fact that cross compiling in Go Just Works and it’s amazing, or cryptographic right answers, or this great diff tool. Usually I don’t want to write a whole blog post about those things because I really don’t have much more to say than “hey this is useful!”

It started to bother me that I didn’t have anywhere to put those things: for example recently I wanted to use diffdiff and I just could not remember what it was called.

the solution: make a new section of this blog

So I quickly made a new folder called /til/, added some custom styling (I wanted to style the posts to look a little bit like a tweet), made a little Rake task to help me create new posts quickly (rake new_til), and set up a separate RSS Feed for it.

I think this new section of the blog might be more for myself than anything, now when I forget the link to Cryptographic Right Answers I can hopefully look it up on the TIL page. (you might think “julia, why not use bookmarks??” but I have been failing to use bookmarks for my whole life and I don’t see that changing ever, putting things in public is for whatever reason much easier for me)

So far it’s been working, often I can actually just make a quick post in 2 minutes which was the goal.

inspired by Simon Willison’s TIL blog

My page is inspired by Simon Willison’s great TIL blog, though my TIL posts are a lot shorter.

I don’t necessarily want everything to be archived

This came about because I spent a lot of time on Twitter, so I’ve been thinking about what I want to do about all of my tweets.

I keep reading the advice to “POSSE” (“post on your own site, syndicate elsewhere”), and while I find the idea appealing in principle, for me part of the appeal of social media is that it’s a little bit ephemeral. I can post polls or questions or observations or jokes and then they can just kind of fade away as they become less relevant.

I find it a lot easier to identify specific categories of things that I actually want to have on a Real Website That I Own:

• blog posts here!
• comics at https://wizardzines.com/comics/!
• now TILs at https://jvns.ca/til/)

and then let everything else be kind of ephemeral.

I really believe in the advice to make email lists though – the first two (blog posts & comics) both have email lists and RSS feeds that people can subscribe to if they want. I might add a quick summary of any TIL posts from that week to the “blog posts from this week” mailing list.

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 all the problems with this diagram that I know about.

You can also view it as an HTML page (I just made it an image so it would show up in RSS).

different kinds of codes are mixed together

The first surprising thing about this diagram to me is that there are 33 control codes, split into (very roughly speaking) these categories:

1. Codes that are handled by the operating system’s terminal driver, for example when the OS sees a 3 (Ctrl-C), it’ll send a SIGINT signal to the current program
2. Everything else is passed through to the application as-is and the application can do whatever it wants with them. Some subcategories of those:
   • Codes that correspond to a literal keypress of a key on your keyboard (Enter, Tab, Backspace). For example when you press Enter, your terminal gets sent 13.
   • Codes used by readline: “the application can do whatever it wants” often means “it’ll do more or less what the readline library does, whether the application actually uses readline or not”, so I’ve labelled a bunch of the codes that readline uses
   • Other codes, for example I think Ctrl-X has no standard meaning in the terminal in general but emacs uses it very heavily

There’s no real structure to which codes are in which categories, they’re all just kind of randomly scattered because this evolved organically.

(If you’re curious about readline, I wrote more about readline in entering text in the terminal is complicated, and there are a lot of cheat sheets out there)

there are only 33 control codes

Something else that I find a little surprising is that are only 33 control codes – A to Z, plus 7 more (@, [, \, ], ^, _, ?). This means that if you want to have for example Ctrl-1 as a keyboard shortcut in a terminal application, that’s not really meaningful – on my machine at least Ctrl-1 is exactly the same thing as just pressing 1, Ctrl-3 is the same as Ctrl-[, etc.

Also Ctrl+Shift+C isn’t a control code – what it does depends on your terminal emulator. On Linux Ctrl-Shift-X is often used by the terminal emulator to copy or open a new tab or paste for example, it’s not sent to the TTY at all.

Also I use Ctrl+Left Arrow all the time, but that isn’t a control code, instead it sends an ANSI escape sequence (ctrl-[[1;5D) which is a different thing which we absolutely do not have space for in this post.

This “there are only 33 codes” thing is totally different from how keyboard shortcuts work in a GUI where you can have Ctrl+KEY for any key you want.

the official ASCII names aren’t very meaningful to me

Each of these 33 control codes has a name in ASCII (for example 3 is ETX). When all of these control codes were originally defined, they weren’t being used for computers or terminals at all, they were used for the telegraph machine. Telegraph machines aren’t the same as UNIX terminals so a lot of the codes were repurposed to mean something else.

Personally I don’t find these ASCII names very useful, because 50% of the time the name in ASCII has no actual relationship to what that code does on UNIX systems today. So it feels easier to just ignore the ASCII names completely instead of trying to figure which ones still match their original meaning.

It’s hard to use Ctrl-M as a keyboard shortcut

Another thing that’s a bit weird is that Ctrl-M is literally the same as Enter, and Ctrl-I is the same as Tab, which makes it hard to use those two as keyboard shortcuts.

From some quick research, it seems like some folks do still use Ctrl-I and Ctrl-M as keyboard shortcuts (here’s an example), but to do that you need to configure your terminal emulator to treat them differently than the default.

For me the main takeaway is that if I ever write a terminal application I should avoid Ctrl-I and Ctrl-M as keyboard shortcuts in it.

how to identify what control codes get sent

While writing this I needed to do a bunch of experimenting to figure out what various key combinations did, so I wrote this Python script echo-key.py that will print them out.

There’s probably a more official way but I appreciated having a script I could customize.

caveat: on canonical vs noncanonical mode

Two of these codes (Ctrl-W and Ctrl-U) are labelled in the table as “handled by the OS”, but actually they’re not always handled by the OS, it depends on whether the terminal is in “canonical” mode or in “noncanonical mode”.

In canonical mode, programs only get input when you press Enter (and the OS is in charge of deleting characters when you press Backspace or Ctrl-W). But in noncanonical mode the program gets input immediately when you press a key, and the Ctrl-W and Ctrl-U codes are passed through to the program to handle any way it wants.

Generally in noncanonical mode the program will handle Ctrl-W and Ctrl-U similarly to how the OS does, but there are some small differences.

Some examples of programs that use canonical mode:

• probably pretty much any noninteractive program, like grep or cat
• git, I think

Examples of programs that use noncanonical mode:

• python3, irb and other REPLs
• your shell
• any full screen TUI like less or vim

caveat: all of the “OS terminal driver” codes are configurable with stty

I said that Ctrl-C sends SIGINT but technically this is not necessarily true, if you really want to you can remap all of the codes labelled “OS terminal driver”, plus Backspace, using a tool called stty, and you can view the mappings with stty -a.

Here are the mappings on my machine right now:

$ stty -a
cchars: discard = ^O; dsusp = ^Y; eof = ^D; eol = <undef>;
	eol2 = <undef>; erase = ^?; intr = ^C; kill = ^U; lnext = ^V;
	min = 1; quit = ^\; reprint = ^R; start = ^Q; status = ^T;
	stop = ^S; susp = ^Z; time = 0; werase = ^W;

I have personally never remapped any of these and I cannot imagine a reason I would (I think it would be a recipe for confusion and disaster for me), but I asked on Mastodon and people said the most common reasons they used stty were:

• fix a broken terminal with stty sane
• set stty erase ^H to change how Backspace works
• set stty ixoff
• some people even map SIGINT to a different key, like their DELETE key

caveat: on signals

Two signals caveats:

1. If the ISIG terminal mode is turned off, then the OS won’t send signals. For example vim turns off ISIG
2. Apparently on BSDs, there’s an extra control code (Ctrl-T) which sends SIGINFO

You can see which terminal modes a program is setting using strace like this, terminal modes are set with the ioctl system call:

$ strace -tt -o out  vim
$ grep ioctl out | grep SET

here are the modes vim sets when it starts (ISIG and ICANON are missing!):

17:43:36.670636 ioctl(0, TCSETS, {c_iflag=IXANY|IMAXBEL|IUTF8,
c_oflag=NL0|CR0|TAB0|BS0|VT0|FF0|OPOST, c_cflag=B38400|CS8|CREAD,
c_lflag=ECHOK|ECHOCTL|ECHOKE|PENDIN, ...}) = 0

and it resets the modes when it exits:

17:43:38.027284 ioctl(0, TCSETS, {c_iflag=ICRNL|IXANY|IMAXBEL|IUTF8,
c_oflag=NL0|CR0|TAB0|BS0|VT0|FF0|OPOST|ONLCR, c_cflag=B38400|CS8|CREAD,
c_lflag=ISIG|ICANON|ECHO|ECHOE|ECHOK|IEXTEN|ECHOCTL|ECHOKE|PENDIN, ...}) = 0

I think the specific combination of modes vim is using here might be called “raw mode”, man cfmakeraw talks about that.

there are a lot of conflicts

Related to “there are only 33 codes”, there are a lot of conflicts where different parts of the system want to use the same code for different things, for example by default Ctrl-S will freeze your screen, but if you turn that off then readline will use Ctrl-S to do a forward search.

Another example is that on my machine sometimes Ctrl-T will send SIGINFO and sometimes it’ll transpose 2 characters and sometimes it’ll do something completely different depending on:

• whether the program has ISIG set
• whether the program uses readline / imitates readline’s behaviour

caveat: on “backspace” and “other backspace”

In this diagram I’ve labelled code 127 as “backspace” and 8 as “other backspace”. Uh, what?

I think this was the single biggest topic of discussion in the replies on Mastodon – apparently there’s a LOT of history to this and I’d never heard of any of it before.

First, here’s how it works on my machine:

1. I press the Backspace key
2. The TTY gets sent the byte 127, which is called DEL in ASCII
3. the OS terminal driver and readline both have 127 mapped to “backspace” (so it works both in canonical mode and noncanonical mode)
4. The previous character gets deleted

If I press Ctrl+H, it has the same effect as Backspace if I’m using readline, but in a program without readline support (like cat for instance), it just prints out ^H.

Apparently Step 2 above is different for some folks – their Backspace key sends the byte 8 instead of 127, and so if they want Backspace to work then they need to configure the OS (using stty) to set erase = ^H.

There’s an incredible section of the Debian Policy Manual on keyboard configuration that describes how Delete and Backspace should work according to Debian policy, which seems very similar to how it works on my Mac today. My understanding (via this mastodon post) is that this policy was written in the 90s because there was a lot of confusion about what Backspace should do in the 90s and there needed to be a standard to get everything to work.

There’s a bunch more historical terminal stuff here but that’s all I’ll say for now.

there’s probably a lot more diversity in how this works

I’ve probably missed a bunch more ways that “how it works on my machine” might be different from how it works on other people’s machines, and I’ve probably made some mistakes about how it works on my machine too. But that’s all I’ve got for today.

Some more stuff I know that I’ve left out: according to stty -a Ctrl-O is “discard”, Ctrl-R is “reprint”, and Ctrl-Y is “dsusp”. I have no idea how to make those actually do anything (pressing them does not do anything obvious, and some people have told me what they used to do historically but it’s not clear to me if they have a use in 2024), and a lot of the time in practice they seem to just be passed through to the application anyway so I just labelled Ctrl-R and Ctrl-Y as readline.

not all of this is that useful to know

Also I want to say that I think the contents of this post are kind of interesting but I don’t think they’re necessarily that useful. I’ve used the terminal pretty successfully every day for the last 20 years without knowing literally any of this – I just knew what Ctrl-C, Ctrl-D, Ctrl-Z, Ctrl-R, Ctrl-L did in practice (plus maybe Ctrl-A, Ctrl-E and Ctrl-W) and did not worry about the details for the most part, and that was almost always totally fine except when I was trying to use xterm.js.

But I had fun learning about it so maybe it’ll be interesting to you too.

This hasn’t been a big priority for me: usually it just goes down for a few minutes while it restarts, and it only happens once a day at most, so I’ve just been ignoring. But last week it started actually causing a problem so I decided to look into it.

This was kind of winding road where I learned a lot so here’s a table of contents:

• there’s about 100MB of memory available
• the problem: OOM killing the backup script
• attempt 1: use SQLite
  • problem: how to store IPv6 addresses
  • problem: it’s 500x slower
  • time for EXPLAIN QUERY PLAN
• attempt 2: use a trie
  • some notes on memory profiling
• attempt 3: make my array use less memory
  • idea 3.1: deduplicate the Name and Country
  • how big are ASNs?
  • idea 3.2: use netip.Addr instead of net.IP
  • the result: saved 70MB of memory!

there’s about 100MB of memory available

I run Mess With DNS on a VM without about 465MB of RAM, which according to ps aux (the RSS column) is split up something like:

• 100MB for PowerDNS
• 200MB for Mess With DNS
• 40MB for hallpass

That leaves about 110MB of memory free.

A while back I set GOMEMLIMIT to 250MB to try to make sure the garbage collector ran if Mess With DNS used more than 250MB of memory, and I think this helped but it didn’t solve everything.

the problem: OOM killing the backup script

A few weeks ago I started backing up Mess With DNS’s database for the first time using restic.

This has been working okay, but since Mess With DNS operates without much extra memory I think restic sometimes needed more memory than was available on the system, and so the backup script sometimes got OOM killed.

This was a problem because

1. backups might be corrupted sometimes
2. more importantly, restic takes out a lock when it runs, and so I’d have to manually do an unlock if I wanted the backups to continue working. Doing manual work like this is the #1 thing I try to avoid with all my web services (who has time for that!) so I really wanted to do something about it.

There’s probably more than one solution to this, but I decided to try to make Mess With DNS use less memory so that there was more available memory on the system, mostly because it seemed like a fun problem to try to solve.

what’s using memory: IP addresses

I’d run a memory profile of Mess With DNS a bunch of times in the past, so I knew exactly what was using most of Mess With DNS’s memory: IP addresses.

When it starts, Mess With DNS loads this database where you can look up the ASN of every IP address into memory, so that when it receives a DNS query it can take the source IP address like 74.125.16.248 and tell you that IP address belongs to GOOGLE.

This database by itself used about 117MB of memory, and a simple du told me that was too much – the original text files were only 37MB!

$ du -sh *.tsv
26M	ip2asn-v4.tsv
11M	ip2asn-v6.tsv

The way it worked originally is that I had an array of these:

type IPRange struct {
	StartIP net.IP
	EndIP   net.IP
	Num     int
	Name    string
	Country string
}

and I searched through it with a binary search to figure out if any of the ranges contained the IP I was looking for. Basically the simplest possible thing and it’s super fast, my machine can do about 9 million lookups per second.

attempt 1: use SQLite

I’ve been using SQLite recently, so my first thought was – maybe I can store all of this data on disk in an SQLite database, give the tables an index, and that’ll use less memory.

So I:

• wrote a quick Python script using sqlite-utils to import the TSV files into an SQLite database
• adjusted my code to select from the database instead

This did solve the initial memory goal (after a GC it now hardly used any memory at all because the table was on disk!), though I’m not sure how much GC churn this solution would cause if we needed to do a lot of queries at once. I did a quick memory profile and it seemed to allocate about 1KB of memory per lookup.

Let’s talk about the issues I ran into with using SQLite though.

problem: how to store IPv6 addresses

SQLite doesn’t have support for big integers and IPv6 addresses are 128 bits, so I decided to store them as text. I think BLOB might have been better, I originally thought BLOBs couldn’t be compared but the sqlite docs say they can.

I ended up with this schema:

CREATE TABLE ipv4_ranges (
   start_ip INTEGER NOT NULL,
   end_ip INTEGER NOT NULL,
   asn INTEGER NOT NULL,
   country TEXT NOT NULL,
   name TEXT NOT NULL
);
CREATE TABLE ipv6_ranges (
   start_ip TEXT NOT NULL,
   end_ip TEXT NOT NULL,
   asn INTEGER,
   country TEXT,
   name TEXT
);
CREATE INDEX idx_ipv4_ranges_start_ip ON ipv4_ranges (start_ip);
CREATE INDEX idx_ipv6_ranges_start_ip ON ipv6_ranges (start_ip);
CREATE INDEX idx_ipv4_ranges_end_ip ON ipv4_ranges (end_ip);
CREATE INDEX idx_ipv6_ranges_end_ip ON ipv6_ranges (end_ip);

Also I learned that Python has an ipaddress module, so I could use ipaddress.ip_address(s).exploded to make sure that the IPv6 addresses were expanded so that a string comparison would compare them properly.

problem: it’s 500x slower

I ran a quick microbenchmark, something like this. It printed out that it could look up 17,000 IPv6 addresses per second, and similarly for IPv4 addresses.

This was pretty discouraging – being able to look up 17k addresses per section is kind of fine (Mess With DNS does not get a lot of traffic), but I compared it to the original binary search code and the original code could do 9 million per second.

	ips := []net.IP{}
	count := 20000
	for i := 0; i < count; i++ {
		// create a random IPv6 address
		bytes := randomBytes()
		ip := net.IP(bytes[:])
		ips = append(ips, ip)
	}
	now := time.Now()
	success := 0
	for _, ip := range ips {
		_, err := ranges.FindASN(ip)
		if err == nil {
			success++
		}
	}
	fmt.Println(success)
	elapsed := time.Since(now)
	fmt.Println("number per second", float64(count)/elapsed.Seconds())

time for EXPLAIN QUERY PLAN

I’d never really done an EXPLAIN in sqlite, so I thought it would be a fun opportunity to see what the query plan was doing.

sqlite> explain query plan select * from ipv6_ranges where '2607:f8b0:4006:0824:0000:0000:0000:200e' BETWEEN start_ip and end_ip;
QUERY PLAN
`--SEARCH ipv6_ranges USING INDEX idx_ipv6_ranges_end_ip (end_ip>?)

It looks like it’s just using the end_ip index and not the start_ip index, so maybe it makes sense that it’s slower than the binary search.

I tried to figure out if there was a way to make SQLite use both indexes, but I couldn’t find one and maybe it knows best anyway.

At this point I gave up on the SQLite solution, I didn’t love that it was slower and also it’s a lot more complex than just doing a binary search. I felt like I’d rather keep something much more similar to the binary search.

A few things I tried with SQLite that did not cause it to use both indexes:

• using a compound index instead of two separate indexes
• running ANALYZE
• using INTERSECT to intersect the results of start_ip < ? and ? < end_ip. This did make it use both indexes, but it also seemed to make the query literally 1000x slower, probably because it needed to create the results of both subqueries in memory and intersect them.

attempt 2: use a trie

My next idea was to use a trie, because I had some vague idea that maybe a trie would use less memory, and I found this library called ipaddress-go that lets you look up IP addresses using a trie.

I tried using it here’s the code, but I think I was doing something wildly wrong because, compared to my naive array + binary search:

• it used WAY more memory (800MB to store just the IPv4 addresses)
• it was a lot slower to do the lookups (it could do only 100K/second instead of 9 million/second)

I’m not really sure what went wrong here but I gave up on this approach and decided to just try to make my array use less memory and stick to a simple binary search.

some notes on memory profiling

One thing I learned about memory profiling is that you can use runtime package to see how much memory is currently allocated in the program. That’s how I got all the memory numbers in this post. Here’s the code:

func memusage() {
	runtime.GC()
	var m runtime.MemStats
	runtime.ReadMemStats(&m)
	fmt.Printf("Alloc = %v MiB\n", m.Alloc/1024/1024)
	// write mem.prof
	f, err := os.Create("mem.prof")
	if err != nil {
		log.Fatal(err)
	}
	pprof.WriteHeapProfile(f)
	f.Close()
}

Also I learned that if you use pprof to analyze a heap profile there are two ways to analyze it: you can pass either --alloc-space or --inuse-space to go tool pprof. I don’t know how I didn’t realize this before but alloc-space will tell you about everything that was allocated, and inuse-space will just include memory that’s currently in use.

Anyway I ran go tool pprof -pdf --inuse_space mem.prof > mem.pdf a lot. Also every time I use pprof I find myself referring to my own intro to pprof, it’s probably the blog post I wrote that I use the most often. I should add --alloc-space and --inuse-space to it.

attempt 3: make my array use less memory

I was storing my ip2asn entries like this:

type IPRange struct {
	StartIP net.IP
	EndIP   net.IP
	Num     int
	Name    string
	Country string
}

I had 3 ideas for ways to improve this:

1. There was a lot of repetition of Name and the Country, because a lot of IP ranges belong to the same ASN
2. net.IP is an []byte under the hood, which felt like it involved an unnecessary pointer, was there a way to inline it into the struct?
3. Maybe I didn’t need both the start IP and the end IP, often the ranges were consecutive so maybe I could rearrange things so that I only had the start IP

idea 3.1: deduplicate the Name and Country

I figured I could store the ASN info in an array, and then just store the index into the array in my IPRange struct. Here are the structs so you can see what I mean:

type IPRange struct {
	StartIP netip.Addr
	EndIP   netip.Addr
	ASN     uint32
	Idx     uint32
}

type ASNInfo struct {
	Country string
	Name    string
}

type ASNPool struct {
	asns   []ASNInfo
	lookup map[ASNInfo]uint32
}

This worked! It brought memory usage from 117MB to 65MB – a 50MB savings. I felt good about this.

Here’s all of the code for that part.

how big are ASNs?

As an aside – I’m storing the ASN in a uint32, is that right? I looked in the ip2asn file and the biggest one seems to be 401307, though there are a few lines that say 4294901931 which is much bigger, but also are just inside the range of a uint32. So I can definitely use a uint32.

59.101.179.0	59.101.179.255	4294901931	Unknown	AS4294901931

idea 3.2: use netip.Addr instead of net.IP

It turns out that I’m not the only one who felt that net.IP was using an unnecessary amount of memory – in 2021 the folks at Tailscale released a new IP address library for Go which solves this and many other issues. They wrote a great blog post about it.

I discovered (to my delight) that not only does this new IP address library exist and do exactly what I want, it’s also now in the Go standard library as netip.Addr. Switching to netip.Addr was very easy and saved another 20MB of memory, bringing us to 46MB.

I didn’t try my third idea (remove the end IP from the struct) because I’d already been programming for long enough on a Saturday morning and I was happy with my progress.

It’s always such a great feeling when I think “hey, I don’t like this, there must be a better way” and then immediately discover that someone has already made the exact thing I want, thought about it a lot more than me, and implemented it much better than I would have.

all of this was messier in real life

Even though I tried to explain this in a simple linear way “I tried X, then I tried Y, then I tried Z”, that’s kind of a lie – I always try to take my actual debugging process (total chaos) and make it seem more linear and understandable because the reality is just too annoying to write down. It’s more like:

• try sqlite
• try a trie
• second guess everything that I concluded about sqlite, go back and look at the results again
• wait what about indexes
• very very belatedly realize that I can use runtime to check how much memory everything is using, start doing that
• look at the trie again, maybe I misunderstood everything
• give up and go back to binary search
• look at all of the numbers for tries/sqlite again to make sure I didn’t misunderstand

A note on using 512MB of memory

Someone asked why I don’t just give the VM more memory. I could very easily afford to pay for a VM with 1GB of memory, but I feel like 512MB really should be enough (and really that 256MB should be enough!) so I’d rather stay inside that constraint. It’s kind of a fun puzzle.

a few ideas from the replies

Folks had a lot of good ideas I hadn’t thought of. Recording them as inspiration if I feel like having another Fun Performance Day at some point.

• Try Go’s unique package for the ASNPool. Someone tried this and it uses more memory, probably because Go’s pointers are 64 bits
• Try compiling with GOARCH=386 to use 32-bit pointers to sace space (maybe in combination with using unique!)
• It should be possible to store all of the IPv6 addresses in just 64 bits, because only the first 64 bits of the address are public
• Interpolation search might be faster than binary search since IP addresses are numeric
• Try the MaxMind db format with mmdbwriter or mmdbctl
• Tailscale’s art routing table package

the result: saved 70MB of memory!

I deployed the new version and now Mess With DNS is using less memory! Hooray!

A few other notes:

• lookups are a little slower – in my microbenchmark they went from 9 million lookups/second to 6 million, maybe because I added a little indirection. Using less memory and a little more CPU seemed like a good tradeoff though.
• it’s still using more memory than the raw text files do (46MB vs 37MB), I guess pointers take up space and that’s okay.

I’m honestly not sure if this will solve all my memory problems, probably not! But I had fun, I learned a few things about SQLite, I still don’t know what to think about tries, and it made me love binary search even more than I already did.

So yesterday I decided to try to upgrade Hugo. There’s no real reason to do this – I’ve been using Hugo version 0.40 to generate this blog since 2018, it works fine, and I don’t have any problems with it. But I thought – maybe it won’t be as hard as I think, and I kind of like a tedious computer task sometimes!

I thought I’d document what I learned along the way in case it’s useful to anyone else doing this very specific migration. I upgraded from Hugo v0.40 (from 2018) to v0.135 (from 2024).

Here are most of the changes I had to make:

change 1: template "theme/partials/thing.html is now partial thing.html

I had to replace a bunch of instances of {{ template "theme/partials/header.html" . }} with {{ partial "header.html" . }}.

This happened in v0.42:

We have now virtualized the filesystems for project and theme files. This makes everything simpler, faster and more powerful. But it also means that template lookups on the form {{ template “theme/partials/pagination.html” . }} will not work anymore. That syntax has never been documented, so it’s not expected to be in wide use.

change 2: .Data.Pages is now site.RegularPages

This seems to be discussed in the release notes for 0.57.2

I just needed to replace .Data.Pages with site.RegularPages in the template on the homepage as well as in my RSS feed template.

change 3: .Next and .Prev got flipped

I had this comment in the part of my theme where I link to the next/previous blog post:

“next” and “previous” in hugo apparently mean the opposite of what I’d think they’d mean intuitively. I’d expect “next” to mean “in the future” and “previous” to mean “in the past” but it’s the opposite

It looks they changed this in ad705aac064 so that “next” actually is in the future and “prev” actually is in the past. I definitely find the new behaviour more intuitive.

downloading the Hugo changelogs with a script

Figuring out why/when all of these changes happened was a little difficult. I ended up hacking together a bash script to download all of the changelogs from github as text files, which I could then grep to try to figure out what happened. It turns out it’s pretty easy to get all of the changelogs from the GitHub API.

So far everything was not so bad – there was also a change around taxonomies that’s I can’t quite explain, but it was all pretty manageable, but then we got to the really tough one: the markdown renderer.

change 4: the markdown renderer (blackfriday -> goldmark)

The blackfriday markdown renderer (which was previously the default) was removed in v0.100.0. This seems pretty reasonable:

It has been deprecated for a long time, its v1 version is not maintained anymore, and there are many known issues. Goldmark should be a mature replacement by now.

Fixing all my Markdown changes was a huge pain – I ended up having to update 80 different Markdown files (out of 700) so that they would render properly, and I’m not totally sure

why bother switching renderers?

The obvious question here is – why bother even trying to upgrade Hugo at all if I have to switch Markdown renderers? My old site was running totally fine and I think it wasn’t necessarily a good use of time, but the one reason I think it might be useful in the future is that the new renderer (goldmark) uses the CommonMark markdown standard, which I’m hoping will be somewhat more futureproof. So maybe I won’t have to go through this again? We’ll see.

Also it turned out that the new Goldmark renderer does fix some problems I had (but didn’t know that I had) with smart quotes and how lists/blockquotes interact.

finding all the Markdown problems: the process

The hard part of this Markdown change was even figuring out what changed. Almost all of the problems (including #2 and #3 above) just silently broke the site, they didn’t cause any errors or anything. So I had to diff the HTML to hunt them down.

Here’s what I ended up doing:

1. Generate the site with the old version, put it in public_old
2. Generate the new version, put it in public
3. Diff every single HTML file in public/ and public_old with this diff.sh script and put the results in a diffs/ folder
4. Run variations on find diffs -type f | xargs cat | grep -C 5 '(31m|32m)' | less -r over and over again to look at every single change until I found something that seemed wrong
5. Update the Markdown to fix the problem
6. Repeat until everything seemed okay

(the grep 31m|32m thing is searching for red/green text in the diff)

This was very time consuming but it was a little bit fun for some reason so I kept doing it until it seemed like nothing too horrible was left.

the new markdown rules

Here’s a list of every type of Markdown change I had to make. It’s very possible these are all extremely specific to me but it took me a long time to figure them all out so maybe this will be helpful to one other person who finds this in the future.

4.1: mixing HTML and markdown

This doesn’t work anymore (it doesn’t expand the link):

<small>
[a link](https://example.com)
</small>

I need to do this instead:

<small>

[a link](https://example.com)

</small>

This works too:

<small> [a link](https://example.com) </small>

4.2: << is changed into «

I didn’t want this so I needed to configure:

markup:
  goldmark:
    extensions:
      typographer:
        leftAngleQuote: '<<'
        rightAngleQuote: '>>'

4.3: nested lists sometimes need 4 space indents

This doesn’t render as a nested list anymore if I only indent by 2 spaces, I need to put 4 spaces.

1. a
  * b
  * c
2. b

The problem is that the amount of indent needed depends on the size of the list markers. Here’s a reference in CommonMark for this.

4.4: blockquotes inside lists work better

Previously the > quote here didn’t render as a blockquote, and with the new renderer it does.

* something
> quote
* something else

I found a bunch of Markdown that had been kind of broken (which I hadn’t noticed) that works better with the new renderer, and this is an example of that.

Lists inside blockquotes also seem to work better.

4.5: headings inside lists

Previously this didn’t render as a heading, but now it does. So I needed to replace the # with #.

* # passengers: 20

4.6: + or 1) at the beginning of the line makes it a list

I had something which looked like this:

`1 / (1
+ exp(-1)) = 0.73`

With Blackfriday it rendered like this:

<p><code>1 / (1
+ exp(-1)) = 0.73</code></p>

and with Goldmark it rendered like this:

<p>`1 / (1</p>
<ul>
<li>exp(-1)) = 0.73`</li>
</ul>

Same thing if there was an accidental 1) at the beginning of a line, like in this Markdown snippet

I set up a small Hadoop cluster (1 master, 2 workers, replication set to 
1) on 

To fix this I just had to rewrap the line so that the + wasn’t the first character.

The Markdown is formatted this way because I wrap my Markdown to 80 characters a lot and the wrapping isn’t very context sensitive.

4.7: no more smart quotes in code blocks

There were a bunch of places where the old renderer (Blackfriday) was doing unwanted things in code blocks like replacing ... with … or replacing quotes with smart quotes. I hadn’t realized this was happening and I was very happy to have it fixed.

4.8: better quote management

The way this gets rendered got better:

"Oh, *interesting*!"

• old: “Oh, interesting!“
• new: “Oh, interesting!”

Before there were two left smart quotes, now the quotes match.

4.9: images are no longer wrapped in a p tag

Previously if I had an image like this:

<img src="https://jvns.ca/images/rustboot1.png">

it would get wrapped in a <p> tag, now it doesn’t anymore. I dealt with this just by adding a margin-bottom: 0.75em to images in the CSS, hopefully that’ll make them display well enough.

4.10: <br> is now wrapped in a p tag

Previously this wouldn’t get wrapped in a p tag, but now it seems to:

<br><br>

I just gave up on fixing this though and resigned myself to maybe having some extra space in some cases. Maybe I’ll try to fix it later if I feel like another yakshave.

4.11: some more goldmark settings

I also needed to

• turn off code highlighting (because it wasn’t working properly and I didn’t have it before anyway)
• use the old “blackfriday” method to generate heading IDs so they didn’t change
• allow raw HTML in my markdown

Here’s what I needed to add to my config.yaml to do all that:

markup:
  highlight:
    codeFences: false
  goldmark:
    renderer:
      unsafe: true
    parser:
      autoHeadingIDType: blackfriday

Maybe I’ll try to get syntax highlighting working one day, who knows. I might prefer having it off though.

a little script to compare blackfriday and goldmark

I also wrote a little program to compare the Blackfriday and Goldmark output for various markdown snippets, here it is in a gist.

It’s not really configured the exact same way Blackfriday and Goldmark were in my Hugo versions, but it was still helpful to have to help me understand what was going on.

a quick note on maintaining themes

My approach to themes in Hugo has been:

1. pay someone to make a nice design for the site (for example wizardzines.com was designed by Melody Starling)
2. use a totally custom theme
3. commit that theme to the same Github repo as the site

So I just need to edit the theme files to fix any problems. Also I wrote a lot of the theme myself so I’m pretty familiar with how it works.

Relying on someone else to keep a theme updated feels kind of scary to me, I think if I were using a third-party theme I’d just copy the code into my site’s github repo and then maintain it myself.

which static site generators have better backwards compatibility?

I asked on Mastodon if anyone had used a static site generator with good backwards compatibility.

The main answers seemed to be Jekyll and 11ty. Several people said they’d been using Jekyll for 10 years without any issues, and 11ty says it has stability as a core goal.

I think a big factor in how appealing Jekyll/11ty are is how easy it is for you to maintain a working Ruby / Node environment on your computer: part of the reason I stopped using Jekyll was that I got tired of having to maintain a working Ruby installation. But I imagine this wouldn’t be a problem for a Ruby or Node developer.

Several people said that they don’t build their Jekyll site locally at all – they just use GitHub Pages to build it.

that’s it!

Overall I’ve been happy with Hugo – I started using it because it had fast build times and it was a static binary, and both of those things are still extremely useful to me. I might have spent 10 hours on this upgrade, but I’ve probably spent 1000+ hours writing blog posts without thinking about Hugo at all so that seems like an extremely reasonable ratio.

I find it hard to be too mad about the backwards incompatible changes, most of them were quite a long time ago, Hugo does a great job of making their old releases available so you can use the old release if you want, and the most difficult one is removing support for the blackfriday Markdown renderer in favour of using something CommonMark-compliant which seems pretty reasonable to me even if it is a huge pain.

But it did take a long time and I don’t think I’d particularly recommend moving 700 blog posts to a new Markdown renderer unless you’re really in the mood for a lot of computer suffering for some reason.

The new renderer did fix a bunch of problems so I think overall it might be a good thing, even if I’ll have to remember to make 2 changes to how I write Markdown (4.1 and 4.3).

Also I’m still using Hugo 0.54 for https://wizardzines.com so maybe these notes will be useful to Future Me if I ever feel like upgrading Hugo for that site.

Hopefully I didn’t break too many things on the blog by doing this, let me know if you see anything broken!

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 fix them.

problem 1: blue on black

One of the top complaints was “blue on black is hard to read”. Here’s an example of that: if I open Terminal.app, set the background to black, and run ls, the directories are displayed in a blue that isn’t that easy to read:

To understand why we’re seeing this blue, let’s talk about ANSI colours!

the 16 ANSI colours

Your terminal has 16 numbered colours – black, red, green, yellow, blue, magenta, cyan, white, and “bright” version of each of those.

Programs can use them by printing out an “ANSI escape code” – for example if you want to see each of the 16 colours in your terminal, you can run this Python program:

def color(num, text):
    return f"\033[38;5;{num}m{text}\033[0m"

for i in range(16):
    print(color(i, f"number {i:02}"))

what are the ANSI colours?

This made me wonder – if blue is colour number 5, who decides what hex color that should correspond to?

The answer seems to be “there’s no standard, terminal emulators just choose colours and it’s not very consistent”. Here’s a screenshot of a table from Wikipedia, where you can see that there’s a lot of variation:

problem 1.5: bright yellow on white

Bright yellow on white is even worse than blue on black, here’s what I get in a terminal with the default settings:

That’s almost impossible to read (and some other colours like light green cause similar issues), so let’s talk about solutions!

two ways to reconfigure your colours

If you’re annoyed by these colour contrast issues (or maybe you just think the default ANSI colours are ugly), you might think – well, I’ll just choose a different “blue” and pick something I like better!

There are two ways you can do this:

Way 1: Configure your terminal emulator: I think most modern terminal emulators have a way to reconfigure the colours, and some of them even come with some preinstalled themes that you might like better than the defaults.

Way 2: Run a shell script: There are ANSI escape codes that you can print out to tell your terminal emulator to reconfigure its colours. Here’s a shell script that does that, from the base16-shell project. You can see that it has a few different conventions for changing the colours – I guess different terminal emulators have different escape codes for changing their colour palette, and so the script is trying to pick the right style of escape code based on the TERM environment variable.

what are the pros and cons of the 2 ways of configuring your colours?

I prefer to use the “shell script” method, because:

• if I switch terminal emulators for some reason, I don’t need to a different configuration system, my colours still Just Work
• I use base16-shell with base16-vim to make my vim colours match my terminal colours, which is convenient

some advantages of configuring colours in your terminal emulator:

• if you use a popular terminal emulator, there are probably a lot more nice terminal themes out there that you can choose from
• not all terminal emulators support the “shell script method”, and even if they do, the results can be a little inconsistent

This is what my shell has looked like for probably the last 5 years (using the solarized light base16 theme), and I’m pretty happy with it. Here’s htop:

Okay, so let’s say you’ve found a terminal colorscheme that you like. What else can go wrong?

problem 2: programs using 256 colours

Here’s what some output of fd, a find alternative, looks like in my colorscheme:

The contrast is pretty bad here, and I definitely don’t have that lime green in my normal colorscheme. What’s going on?

We can see what color codes fd is using using the unbuffer program to capture its output including the color codes:

$ unbuffer fd . > out
$ vim out
^[[38;5;48mbad-again.sh^[[0m
^[[38;5;48mbad.sh^[[0m
^[[38;5;48mbetter.sh^[[0m
out

^[[38;5;48 means “set the foreground color to color 48”. Terminals don’t only have 16 colours – many terminals these days actually have 3 ways of specifying colours:

1. the 16 ANSI colours we already talked about
2. an extended set of 256 colours
3. a further extended set of 24-bit hex colours, like #ffea03

So fd is using one of the colours from the extended 256-color set. bat (a cat alternative) does something similar – here’s what it looks like by default in my terminal.

This looks fine though and it really seems like it’s trying to work well with a variety of terminal themes.

some newer tools seem to have theme support

I think it’s interesting that some of these newer terminal tools (fd, cat, delta, and probably more) have support for arbitrary custom themes. I guess the downside of this approach is that the default theme might clash with your terminal’s background, but the upside is that it gives you a lot more control over theming the tool’s output than just choosing 16 ANSI colours.

I don’t really use bat, but if I did I’d probably use bat --theme ansi to just use the ANSI colours that I have set in my normal terminal colorscheme.

problem 3: the grays in Solarized

A bunch of people on Mastodon mentioned a specific issue with grays in the Solarized theme: when I list a directory, the base16 Solarized Light theme looks like this:

but iTerm’s default Solarized Light theme looks like this:

This is because in the iTerm theme (which is the original Solarized design), colors 9-14 (the “bright blue”, “bright red”, etc) are mapped to a series of grays, and when I run ls, it’s trying to use those “bright” colours to color my directories and executables.

My best guess for why the original Solarized theme is designed this way is to make the grays available to the vim Solarized colorscheme.

I’m pretty sure I prefer the modified base16 version I use where the “bright” colours are actually colours instead of all being shades of gray though. (I didn’t actually realize the version I was using wasn’t the “original” Solarized theme until I wrote this post)

In any case I really love Solarized and I’m very happy it exists so that I can use a modified version of it.

problem 4: a vim theme that doesn’t match the terminal background

If I my vim theme has a different background colour than my terminal theme, I get this ugly border, like this:

This one is a pretty minor issue though and I think making your terminal background match your vim background is pretty straightforward.

problem 5: programs setting a background color

A few people mentioned problems with terminal applications setting an unwanted background colour, so let’s look at an example of that.

Here ngrok has set the background to color #16 (“black”), but the base16-shell script I use sets color 16 to be bright orange, so I get this, which is pretty bad:

I think the intention is for ngrok to look something like this:

I think base16-shell sets color #16 to orange (instead of black) so that it can provide extra colours for use by base16-vim. This feels reasonable to me – I use base16-vim in the terminal, so I guess I’m using that feature and it’s probably more important to me than ngrok (which I rarely use) behaving a bit weirdly.

This particular issue is a maybe obscure clash between ngrok and my colorschem, but I think this kind of clash is pretty common when a program sets an ANSI background color that the user has remapped for some reason.

a nice solution to contrast issues: “minimum contrast”

A bunch of terminals (iTerm2, tabby, kitty’s text_fg_override_threshold, and folks tell me also Ghostty and Windows Terminal) have a “minimum contrast” feature that will automatically adjust colours to make sure they have enough contrast.

Here’s an example from iTerm. This ngrok accident from before has pretty bad contrast, I find it pretty difficult to read:

With “minimum contrast” set to 40 in iTerm, it looks like this instead:

I didn’t have minimum contrast turned on before but I just turned it on today because it makes such a big difference when something goes wrong with colours in the terminal.

problem 6: TERM being set to the wrong thing

A few people mentioned that they’ll SSH into a system that doesn’t support the TERM environment variable that they have set locally, and then the colours won’t work.

I think the way TERM works is that systems have a terminfo database, so if the value of the TERM environment variable isn’t in the system’s terminfo database, then it won’t know how to output colours for that terminal. I don’t know too much about terminfo, but someone linked me to this terminfo rant that talks about a few other issues with terminfo.

I don’t have a system on hand to reproduce this one so I can’t say for sure how to fix it, but this stackoverflow question suggests running something like TERM=xterm ssh instead of ssh.

problem 7: picking “good” colours is hard

A couple of problems people mentioned with designing / finding terminal colorschemes:

• some folks are colorblind and have trouble finding an appropriate colorscheme
• accidentally making the background color too close to the cursor or selection color, so they’re hard to find
• generally finding colours that work with every program is a struggle (for example you can see me having a problem with this with ngrok above!)

problem 8: making nethack/mc look right

Another problem people mentioned is using a program like nethack or midnight commander which you might expect to have a specific colourscheme based on the default ANSI terminal colours.

For example, midnight commander has a really specific classic look:

But in my Solarized theme, midnight commander looks like this:

The Solarized version feels like it could be disorienting if you’re very used to the “classic” look.

One solution Simon Tatham mentioned to this is using some palette customization ANSI codes (like the ones base16 uses that I talked about earlier) to change the color palette right before starting the program, for example remapping yellow to a brighter yellow before starting Nethack so that the yellow characters look better.

problem 9: commands disabling colours when writing to a pipe

If I run fd | less, I see something like this, with the colours disabled.

In general I find this useful – if I pipe a command to grep, I don’t want it to print out all those color escape codes, I just want the plain text. But what if you want to see the colours?

To see the colours, you can run unbuffer fd | less -r! I just learned about unbuffer recently and I think it’s really cool, unbuffer opens a tty for the command to write to so that it thinks it’s writing to a TTY. It also fixes issues with programs buffering their output when writing to a pipe, which is why it’s called unbuffer.

Here’s what the output of unbuffer fd | less -r looks like for me:

Also some commands (including fd) support a --color=always flag which will force them to always print out the colours.

problem 10: unwanted colour in ls and other commands

Some people mentioned that they don’t want ls to use colour at all, perhaps because ls uses blue, it’s hard to read on black, and maybe they don’t feel like customizing their terminal’s colourscheme to make the blue more readable or just don’t find the use of colour helpful.

Some possible solutions to this one:

• you can run ls --color=never, which is probably easiest
• you can also set LS_COLORS to customize the colours used by ls. I think some other programs other than ls support the LS_COLORS environment variable too.
• also some programs support setting NO_COLOR=true (there’s a list here)

Here’s an example of running LS_COLORS="fi=0:di=0:ln=0:pi=0:so=0:bd=0:cd=0:or=0:ex=0" ls:

problem 11: the colours in vim

I used to have a lot of problems with configuring my colours in vim – I’d set up my terminal colours in a way that I thought was okay, and then I’d start vim and it would just be a disaster.

I think what was going on here is that today, there are two ways to set up a vim colorscheme in the terminal:

1. using your ANSI terminal colours – you tell vim which ANSI colour number to use for the background, for functions, etc.
2. using 24-bit hex colours – instead of ANSI terminal colours, the vim colorscheme can use hex codes like #faea99 directly

20 years ago when I started using vim, terminals with 24-bit hex color support were a lot less common (or maybe they didn’t exist at all), and vim certainly didn’t have support for using 24-bit colour in the terminal. From some quick searching through git, it looks like vim added support for 24-bit colour in 2016 – just 8 years ago!

So to get colours to work properly in vim before 2016, you needed to synchronize your terminal colorscheme and your vim colorscheme. Here’s what that looked like, the colorscheme needed to map the vim color classes like cterm05 to ANSI colour numbers.

But in 2024, the story is really different! Vim (and Neovim, which I use now) support 24-bit colours, and as of Neovim 0.10 (released in May 2024), the termguicolors setting (which tells Vim to use 24-bit hex colours for colorschemes) is turned on by default in any terminal with 24-bit color support.

So this “you need to synchronize your terminal colorscheme and your vim colorscheme” problem is not an issue anymore for me in 2024, since I don’t plan to use terminals without 24-bit color support in the future.

The biggest consequence for me of this whole thing is that I don’t need base16 to set colors 16-21 to weird stuff anymore to integrate with vim – I can just use a terminal theme and a vim theme, and as long as the two themes use similar colours (so it’s not jarring for me to switch between them) there’s no problem. I think I can just remove those parts from my base16 shell script and totally avoid the problem with ngrok and the weird orange background I talked about above.

some more problems I left out

I think there are a lot of issues around the intersection of multiple programs, like using some combination tmux/ssh/vim that I couldn’t figure out how to reproduce well enough to talk about them. Also I’m sure I missed a lot of other things too.

base16 has really worked for me

I’ve personally had a lot of success with using base16-shell with base16-vim – I just need to add a couple of lines to my fish config to set it up (+ a few .vimrc lines) and then I can move on and accept any remaining problems that that doesn’t solve.

I don’t think base16 is for everyone though, some limitations I’m aware of with base16 that might make it not work for you:

• it comes with a limited set of builtin themes and you might not like any of them
• the Solarized base16 theme (and maybe all of the themes?) sets the “bright” ANSI colours to be exactly the same as the normal colours, which might cause a problem if you’re relying on the “bright” colours to be different from the regular ones
• it sets colours 16-21 in order to give the vim colorschemes from base16-vim access to more colours, which might not be relevant if you always use a terminal with 24-bit color support, and can cause problems like the ngrok issue above
• also the way it sets colours 16-21 could be a problem in terminals that don’t have 256-color support, like the linux framebuffer terminal

Apparently there’s a community fork of base16 called tinted-theming, which I haven’t looked into much yet.

some other colorscheme tools

Just one so far but I’ll link more if people tell me about them:

• rootloops.sh for generating colorschemes (and “let’s create a terminal color scheme”)
• Some popular colorschemes (according to people I asked on Mastodon): catpuccin, Monokai, Gruvbox, Dracula, Modus (a high contrast theme), Tokyo Night, Nord, Rosé Pine

okay, that was a lot

We talked about a lot in this post and while I think learning about all these details is kind of fun if I’m in the mood to do a deep dive, I find it SO FRUSTRATING to deal with it when I just want my colours to work! Being surprised by unreadable text and having to find a workaround is just not my idea of a good day.

Personally I’m a zero-configuration kind of person and it’s not that appealing to me to have to put together a lot of custom configuration just to make my colours in the terminal look acceptable. I’d much rather just have some reasonable defaults that I don’t have to change.

minimum contrast seems like an amazing feature

My one big takeaway from writing this was to turn on “minimum contrast” in my terminal, I think it’s going to fix most of the occasional accidental unreadable text issues I run into and I’m pretty excited about it.

go 1.22 now has better routing

I’ve never felt motivated to learn any of the Go routing libraries (gorilla/mux, chi, etc), so I’ve been doing all my routing by hand, like this.

	// DELETE /records:
	case r.Method == "DELETE" && n == 1 && p[0] == "records":
		if !requireLogin(username, r.URL.Path, r, w) {
			return
		}
		deleteAllRecords(ctx, username, rs, w, r)
	// POST /records/<ID>
	case r.Method == "POST" && n == 2 && p[0] == "records" && len(p[1]) > 0:
		if !requireLogin(username, r.URL.Path, r, w) {
			return
		}
		updateRecord(ctx, username, p[1], rs, w, r)

But apparently as of Go 1.22, Go now has better support for routing in the standard library, so that code can be rewritten something like this:

	mux.HandleFunc("DELETE /records/", app.deleteAllRecords)
	mux.HandleFunc("POST /records/{record_id}", app.updateRecord)

Though it would also need a login middleware, so maybe something more like this, with a requireLogin middleware.

	mux.Handle("DELETE /records/", requireLogin(http.HandlerFunc(app.deleteAllRecords)))

a gotcha with the built-in router: redirects with trailing slashes

One annoying gotcha I ran into was: if I make a route for /records/, then a request for /records will be redirected to /records/.

I ran into an issue with this where sending a POST request to /records redirected to a GET request for /records/, which broke the POST request because it removed the request body. Thankfully Xe Iaso wrote a blog post about the exact same issue which made it easier to debug.

I think the solution to this is just to use API endpoints like POST /records instead of POST /records/, which seems like a more normal design anyway.

sqlc automatically generates code for my db queries

I got a little bit tired of writing so much boilerplate for my SQL queries, but I didn’t really feel like learning an ORM, because I know what SQL queries I want to write, and I didn’t feel like learning the ORM’s conventions for translating things into SQL queries.

But then I found sqlc, which will compile a query like this:

-- name: GetVariant :one
SELECT *
FROM variants
WHERE id = ?;

into Go code like this:

const getVariant = `-- name: GetVariant :one
SELECT id, created_at, updated_at, disabled, product_name, variant_name
FROM variants
WHERE id = ?
`

func (q *Queries) GetVariant(ctx context.Context, id int64) (Variant, error) {
	row := q.db.QueryRowContext(ctx, getVariant, id)
	var i Variant
	err := row.Scan(
		&i.ID,
		&i.CreatedAt,
		&i.UpdatedAt,
		&i.Disabled,
		&i.ProductName,
		&i.VariantName,
	)
	return i, err
}

What I like about this is that if I’m ever unsure about what Go code to write for a given SQL query, I can just write the query I want, read the generated function and it’ll tell me exactly what to do to call it. It feels much easier to me than trying to dig through the ORM’s documentation to figure out how to construct the SQL query I want.

Reading Brandur’s sqlc notes from 2024 also gave me some confidence that this is a workable path for my tiny programs. That post gives a really helpful example of how to conditionally update fields in a table using CASE statements (for example if you have a table with 20 columns and you only want to update 3 of them).

sqlite tips

Someone on Mastodon linked me to this post called Optimizing sqlite for servers. My projects are small and I’m not so concerned about performance, but my main takeaways were:

• have a dedicated object for writing to the database, and run db.SetMaxOpenConns(1) on it. I learned the hard way that if I don’t do this then I’ll get SQLITE_BUSY errors from two threads trying to write to the db at the same time.
• if I want to make reads faster, I could have 2 separate db objects, one for writing and one for reading

There are a more tips in that post that seem useful (like “COUNT queries are slow” and “Use STRICT tables”), but I haven’t done those yet.

Also sometimes if I have two tables where I know I’ll never need to do a JOIN beteween them, I’ll just put them in separate databases so that I can connect to them independently.

Go 1.19 introduced a way to set a GC memory limit

I run all of my Go projects in VMs with relatively little memory, like 256MB or 512MB. I ran into an issue where my application kept getting OOM killed and it was confusing – did I have a memory leak? What?

After some Googling, I realized that maybe I didn’t have a memory leak, maybe I just needed to reconfigure the garbage collector! It turns out that by default (according to A Guide to the Go Garbage Collector), Go’s garbage collector will let the application allocate memory up to 2x the current heap size.

Mess With DNS’s base heap size is around 170MB and the amount of memory free on the VM is around 160MB right now, so if its memory doubled, it’ll get OOM killed.

In Go 1.19, they added a way to tell Go “hey, if the application starts using this much memory, run a GC”. So I set the GC memory limit to 250MB and it seems to have resulted in the application getting OOM killed less often:

export GOMEMLIMIT=250MiB

some reasons I like making websites in Go

I’ve been making tiny websites (like the nginx playground) in Go on and off for the last 4 years or so and it’s really been working for me. I think I like it because:

• there’s just 1 static binary, all I need to do to deploy it is copy the binary. If there are static files I can just embed them in the binary with embed.
• there’s a built-in webserver that’s okay to use in production, so I don’t need to configure WSGI or whatever to get it to work. I can just put it behind Caddy or run it on fly.io or whatever.
• Go’s toolchain is very easy to install, I can just do apt-get install golang-go or whatever and then a go build will build my project
• it feels like there’s very little to remember to start sending HTTP responses – basically all there is are functions like Serve(w http.ResponseWriter, r *http.Request) which read the request and send a response. If I need to remember some detail of how exactly that’s accomplished, I just have to read the function!
• also net/http is in the standard library, so you can start making websites without installing any libraries at all. I really appreciate this one.
• Go is a pretty systems-y language, so if I need to run an ioctl or something that’s easy to do

In general everything about it feels like it makes projects easy to work on for 5 days, abandon for 2 years, and then get back into writing code without a lot of problems.

For contrast, I’ve tried to learn Rails a couple of times and I really want to love Rails – I’ve made a couple of toy websites in Rails and it’s always felt like a really magical experience. But ultimately when I come back to those projects I can’t remember how anything works and I just end up giving up. It feels easier to me to come back to my Go projects that are full of a lot of repetitive boilerplate, because at least I can read the code and figure out how it works.

things I haven’t figured out yet

some things I haven’t done much of yet in Go:

• rendering HTML templates: usually my Go servers are just APIs and I make the frontend a single-page app with Vue. I’ve used html/template a lot in Hugo (which I’ve used for this blog for the last 8 years) but I’m still not sure how I feel about it.
• I’ve never made a real login system, usually my servers don’t have users at all.
• I’ve never tried to implement CSRF

In general I’m not sure how to implement security-sensitive features so I don’t start projects which need login/CSRF/etc. I imagine this is where a framework would help.

it’s cool to see the new features Go has been adding

Both of the Go features I mentioned in this post (GOMEMLIMIT and the routing) are new in the last couple of years and I didn’t notice when they came out. It makes me think I should pay closer attention to the release notes for new Go versions.