iiinova — where your digital self keeps evolving

Julia's Reruns Bot @b0rk-reruns.jvns.ca · 13/10/2026

floating point permalink: wizardzines.com/comics/floating-poi… from our zine Bite Size Linux!: wizardzines.com/zines/bite-size-lin…

$### a double is 64 bits ``` 10011011 10011011 10011011 1011011 10011011 10011011 10011011 1011011 ``` (the first digit is the sign, the next 11 digits are the exponent, the rest is the fraction) ± 2 ^ E - 1023 x 1.frac That means there are 2^64 doubles. The biggest one is about 2^1023 ### weird double arithmetic 2^52 + 0.2 = 2^52 (the next number after 2^52 is 2^52 + 1) ### doubles get farther apart as they get bigger betweeen 2^n and 2^n+1 there are always 2^52 doubles, evenly spaced that means that the next double after 2^60 is 2^60 =64 (2^60 / 2^52) ### Javascript *only* has doubles (no integers!) > 2**53 9007199254740992 > 2**53+1 9007199254740992 (same number! uh oh!) ### panel 5 person with short spiky hair, baffled: doubles are scary and their arithmetic is weird! person with short curly hair, calm and reassuring: they're very logical! just understand how they work and don't use integers over 2^53 in Javascript <3$

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Julia's Reruns Bot @b0rk-reruns.jvns.ca · 15/09/2026

your domain's authoritative nameservers permalink: wizardzines.com/comics/your-domains… from our zine How DNS Works: wizardzines.com/zines/dns

### when you register a domain, your registrar runs your authoritative nameservers by default
your registrar, represented by a box with a smiley face wearing a crown: I'm taking care of your DNS!

You can change your nameservers in your registrar's control panel.

### LOTS of services can be your authoritative nameserver
your registrar: I can manage your DNS records!
AWS, also represented by a box with a smiley face wearing a crown: me too!
shopify, also also represented by a box with a smiley face wearing a crown: me three!

Nonplussed stick figure with curly hair: ok chill I only need one of you to do it

### how to find your domain's nameservers
```
$ dig +short NS neopets.com
ns-42.awsdns-05.com.
ns-1191.awsdns-20.org.
```
`neopets.com` is using AWS's nameservers right now

### how to change your nameservers
1. Copy your DNS records to the new nameservers (use dig to check that it worked) 2. On your registrar's website, update your nameservers
3. Wait 48 hours
4. Delete the

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Julia's Reruns Bot @b0rk-reruns.jvns.ca · 13/09/2026

why DNS updates are slow: caching permalink: wizardzines.com/comics/why-dns-upda… from our zine How DNS Works: wizardzines.com/zines/dns

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Julia's Reruns Bot @b0rk-reruns.jvns.ca · 05/09/2026

sed permalink: wizardzines.com/comics/sed from our zine Bite Size Command Line!: wizardzines.com/zines/bite-size-com…

$### sed is most often used for replacing text in a file `$ sed s/cat/dog/g file.txt` "cat"can be a regular expression ### change a file in place. with -i person: in GNU sed it's -i, in BSD sed, -i SUFFIX confuses me every time. ### Some more sed incantations... ### sed -n 12 p print 12th line -n suppresses output so only what you print with 'p' gets printed ### sed 5 d delete 5th line ### sed /cat/d delete lines matching /cat/ ### sed -n 5,30 p print lines 5-30 ### sed s+cat/+dog/+ ('+' can be any character) Use + as a regex delimeter person: way easier than escaping /s like s/cat\//dog\//! ### sed -n s/cat/dog/p only print changed lines. ### sed G double space a file (good for long error lines) ### sed /cat la dog' append 'dog' after lines containing 'cat' ### sed 'i 17 panda" insert "panda" on line 17$

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Julia's Reruns Bot @b0rk-reruns.jvns.ca · 22/08/2026

using HTTP APIs permalink: wizardzines.com/comics/http-apis from our zine HTTP: Learn your browser's language!: wizardzines.com/zines/http

Lots of services (Twitter! Twilio! Google!) let you use them by sending them HTTP requests. If an HTTP API doesn't come with a client library, don't be scared! You can just make the HTTP requests yourself. Here's what you need to remember:

### Set the right `Content—Type` header
Often you'll be sending a POST request with a body, and that means you need a `Content—Type` header that matches the body.

The 2 main options are:
- `application/json` (JSON!)
- `application/x-www-form-urlencoded` (same as what an HTML form does)

If you don't set the `Content—Type`, your request won't work.

Smiling stick figure with short curly hair: a common error is to try to send POST data as one content type (like JSON) when it's actually another (like application/x-www-form-urlencoded)

### Identify yourself
Most HTTP APIs require a secret API key so they know who you are.
Here's how that looks for the Twilio API:
```
curl
https://api.twilio.com/2010-04-01/Accounts/ACCOUNT_ID/Messages.json
-H "Cont

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Julia's Reruns Bot @b0rk-reruns.jvns.ca · 20/08/2026

the same-origin policy permalink: wizardzines.com/comics/same-origin-… from our zine HTTP: Learn your browser's language!: wizardzines.com/zines/http

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Julia's Reruns Bot @b0rk-reruns.jvns.ca · 18/08/2026

the most important HTTP request headers permalink: wizardzines.com/comics/request-head… from our zine HTTP: Learn your browser's language!: wizardzines.com/zines/http

These are the most important request headers:

### Host
The domain
The only required header.
`Host: examplecat.com`

### User-Agent
name + version of your browser and OS
`User-Agent: curl 7.0.2`

### Referer
(yes, it's misspelled!)
website that linked or included the resource
`Referer: http://examplecat.com`

### Authorization
eg a password or API token
base64 encoded user: password
`Authorization: Basic YXZ`

### Cookie
send cookies the server sent you earlier
keeps you logged in
`Cookie: user=b0rk`

### Range
lets you continue downlats ("get bytes 100-200")
`Range: bytes=100-200`

### Cache-Control
"max-age=60"
means cached responses must be less than 60 seconds old

### If-Modified-Since
only send if resource was modified after this time
`If-Modified-Since: Wed, 21 Oct...`

### If-None-Match
only send if the ETag doesn't match those listed
`If-None-Match: "e7ddac"`

### Accept
MIME type you want the response to be
`Accept: image/png`

### Acce

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Julia's Reruns Bot @b0rk-reruns.jvns.ca · 16/08/2026

http status codes permalink: wizardzines.com/comics/status-codes from our zine HTTP: Learn your browser's language!: wizardzines.com/zines/http

Every HTTP response has a status code.
browser, optimistically: `GET /cat.png` (request)
server, sadly: 404 not found (404 is the status code!)

There are 50ish status codes but these are the most common ones in real life:

2xxs mean ★Success★
- 200 OK

3xx s aren't errors, just redirects to somewhere else
- 301 Moved Permanently
- 302 Found: temporary redirect
- 304 Not Modified: the client already has the latest version, "redirect" to that

4xx errors are generally the client's fault: it made some kind of invalid request
- 400 Bad Request
- 403 Forbidden: API key/OAuth/something needed
- 404 Not Found: we all know this one :)
- 429 Too Many Requests: you're being rate limited

5xx errors generally mean something's wrong with the server.
- 500 Internal Server Error: the server code has an error
- 503 Service Unavailable: could mean nginx (or whatever proxy) couldn't connect to the server
- 504 Gateway Timeout: the server was too slow to respond

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Julia's Reruns Bot @b0rk-reruns.jvns.ca · 29/07/2026

anatomy of a HTTP response permalink: wizardzines.com/comics/anatomy-http… from our zine HTTP: Learn your browser's language!: wizardzines.com/zines/http

### HTTP responses have:
- a status code (200 OK! 404 not found!)
- headers
- a body (HTML, an image, JSON, etc)

### Here's the HTTP response from `examplecat.com/cat.txt`:
```
HTTP/1.1 200 OK
status
Accept-Ranges: bytes
Cache-Control: public, max-age=0
Content-Length: 33
Content-Type: text/plain; charset=UTF-8 Date: Mon, 09 Sep 2019 01:57:35 GMT
Etag: "ac5affa59f554a1440043537ae973790-ssl"
Strict-Transport-Security: max-age=31536000
Age: 0
Server: Netlify
[ASCII image of a cat, labelled "cat!" with a smiley face]
```
The first line, `HTTP/1.1 200 OK` is the status code. "200" is the status.

The lines from `Accept-Ranges` to `Server` are the headers.

The cat picture is the body.

### There are a few kinds of response headers:

- when the resource was sent/modified:
```
Date: Mon, 09 Sep 2019 01:57:35 GMT
Last-Modified: 3 Feb 2017 13:00:00 GMT
```

- about the response body:
```
Content-Language: en-US
Content-Length: 33
Content-Type: text/plain; charset=UTF-8
Content-Encoding: g

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Julia's Reruns Bot @b0rk-reruns.jvns.ca · 27/07/2026

TLS certificates permalink: wizardzines.com/comics/certificates from our zine HTTP: Learn your browser's language!: wizardzines.com/zines/http

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Julia's Reruns Bot @b0rk-reruns.jvns.ca · 23/07/2026

HTTP/2 permalink: wizardzines.com/comics/http2 from our zine HTTP: Learn your browser's language!: wizardzines.com/zines/http

HTTP/2 is a new version of HTTP. Here's what you need to know:

### A lot isn't changing
All the methods, status codes, request/response bodies, and headers mean exactly the same thing in HTTP/2.

before (HTTP/1.1):
```
method: GET
path: /cat.gif
headers:
- Host: examplecat.com
- User-Agent: curl
```

after (HTTP/2):
```
method: GET
path: /cat.gif
authority: examplecat.com
headers:
- User-Agent: curl
```

one change:
Host header => authority

#### HTTP/2 is faster
Even though the data sent is the same, the way HTTP/2 sends it is different. The main differences are:
- It's a binary format (it's harder to ```tcpdump``` traffic and debug)
- Headers are compressed
- Multiple requests can be sent on the same connection at a time

before (HTTP/1.1):
→ request 1
response 1 ←
→ request 2
response 2 ←

after (HTTP/2):
→ request 1
→ request 2
response 2 ←
response 1 ← (out of order is ok)
(one TCP connection)

All these changes together mean that HTTP/2

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Julia's Reruns Bot @b0rk-reruns.jvns.ca · 17/07/2026

non-POSIX features permalink: wizardzines.com/comics/bashisms from our zine Bite Size Bash!: wizardzines.com/zines/bite-size-bash

$### some bash features aren't in the POSIX spec Illustration of a smiling stick figure with curly hair. Person: here are some examples! These won't work in POSIX shells like `dash` and `sh`. ### arrays POSIX shells only have one array: `$@` for arguments ### [[ $DIR=/home/*]] POSIX alternative: match strings with `grep` ### [[ ... ]] POSIX alternative: `[ ... ]` ### diff <(./cmd1) <./cmd2) this is called "process substitution", you can use named pipes instead ### the local Keyword in POSIX shells, all variables are global ### for ((i=0; i <3; i++)) `sh` only has for `x` in ... loops, not C-style loops ### a. {png, svg} you'll have to type `a.png a.svg` ### {1..5} POSIX alternative: `$(seq 1 5)` ### $'\n' POSIX alternative: `$(printf "\n")` ### ${var//search/replace} POSIX alternative: pipe to `sed`$

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Julia's Reruns Bot @b0rk-reruns.jvns.ca · 15/07/2026

environment variables permalink: wizardzines.com/comics/environment-… from our zine Bite Size Bash!: wizardzines.com/zines/bite-size-bash

$### panel 1: every process has environment variables how to see any process's environment variables on Linux: ``` cat /proc/$PID/environ | tr '\0' '\n' ``` ### panel 2: shell scripts have 2 kinds of variables 1. environment variables 2. shell variables unlike in most languages, in shell you access both of these in the exact same way: `$VARIABLE` ### panel 3: export sets environment variables ``` export ANIMAL=panda ``` `export ANIMAL=panda` means that every child process will have `ANIMAL` set to `panda` ### panel 4: child processes inherit environment variables this is wy the variables set in your `.bash_profile` work in all programs you start from the terminal. They're all child processes of your bash shell! ### panel 5: shell variables aren't inherited ``` var=panda ``` in this example, `$var` only gets set in this process, not in child processes ### panel 6: you can set environment variables when starting a program Illustration of a smiling stick figure with curly$

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