TIL

Today I Learned

awk

• Field Variables - 2025-05-21

bash

• Use the DEBUG Trap to Step Through a Script - 2020-10-19
• Always Enclose Variable Names in Double Quotes - 2021-07-19
• Shell Script Template - 2024-08-21
• Default Error Behavior - 2024-08-25
• Use the timeout command to limit execution time - 2025-06-13

character-encoding

• = Serves as Padding in Base64 Encoded Strings - 2020-07-01
• Unicode playing cards layout - 2025-07-11

chrome

• Use Logpoints to Log Messages to the Console - 2020-05-03
• Use DevTools to Take Screenshots - 2020-07-05

clis-and-terminals

• Use Commonly Available Characters for Progress Indicators - 2022-01-09
• - - 2024-05-11

cloudflare

• Implement GraphQL Servers in Cloudflare Workers - 2020-07-27

css

• Upside Down Table Trick - 2024-08-28
• grid-area - 2024-09-02
• Blurry Image Placeholders - 2025-05-15
• Regex-Flavored Attribute Selectors in CSS - 2025-06-11
• text-wrap: balance for Better Layouts - 2025-06-12
• Transform Origin Changes Animation Behavior - 2025-07-09

curl

• Useful HTTP Flags - 2021-06-28

django

• Django Drops the SQL DEFAULT Constraint When Creating New Columns - 2022-01-27
• {% querystring %} Template Tag - 2024-09-02

docker

• Enable Long-Lived Container Logs - 2022-11-02

emacs

• Remove All Newlines from a Selected Region - 2020-10-17
• Remove All Whitespace from Beginning of All Lines - 2020-10-18
• Update Feature Branch to Latest main - 2021-03-31
• Insert Detailed Timestamps - 2024-05-13

git

• Push an Empty Commit - 2020-05-05
• Use Exclamation Marks in Commit Messages - 2020-05-05
• Use Multiple git commit Message Flags to Create Multiline Commits - 2020-07-12
• The Differences Between .git/info/exclude and .gitignore - 2020-08-02
• Git Only Stores Timestamps and Author Information on Commits - 2020-08-02
• Set Default for Initial Branch Name - 2020-08-09
• Move a Range of Commits Between Branches - 2021-03-31
• Move Individual Commits Between Branches with cherry-pick - 2021-03-31
• Get Earliest Commit Over Time Range - 2024-08-26
• Use stage Instead of add for Clarity - 2025-07-11

github

• Use the Fuzzy File Finder to Navigate Repos - 2020-05-03
• Use Relative Paths to Link to Wiki Pages from README.md - 2020-07-11
• Create New Gists and Repos with .new URLs - 2020-07-18

go

• Create Multiline Strings Using Backticks - 2020-07-28
• Concatenate Strings Efficiently with bytes.Buffer and strings.Builder - 2020-07-28

graphical-control-elements

• Throbber - 2021-06-28

grep

• grep: Extended Regex with -E Flag - 2025-07-10
• grep: Ignore Case with -i Flag - 2025-07-10
• grep: Invert Match with -v Flag - 2025-07-10
• grep: List Matching Files with -l Flag - 2025-07-10
• grep: Match Whole Words with -w Flag - 2025-07-10
• grep: Output Only Matches with -o Flag - 2025-07-10
• Basic vs extended regular expressions in grep - 2025-07-13
• grep: Recursive Search with -r Flag - 2025-07-14
• grep: Show Context Lines with -C Flag - 2025-07-14
• grep: Show Lines After Match with -A Flag - 2025-07-14
• grep: Show Lines Before Match with -B Flag - 2025-07-14
• grep: Skip Binary Files with -I Flag - 2025-07-14
• grep: Suppress Filenames with -h Flag - 2025-07-14

haskell

• String Concatenation Operators - 2024-08-12

html

• <h1> Element Explicit Styling - 2025-06-12

http

• CORS Preflight Requests Communicate Which Methods and Headers a Server Should Allow - 2020-06-30
• Trigger Opt-in File Downloads with the Content-Disposition Response Header - 2020-10-18

javascript

• Inconsistencies in Date - 2020-08-03
• Use Numeric Separators to Parse Large Numbers by Eye - 2020-08-09
• Disable Jest's Auto-generated Coverage Reports - 2020-08-29
• Dates as Keys are not Equal - 2021-02-07
• Canceling Asynchronous Threads Can Be Tricky - 2021-02-07
• Every Readable Stream is Asynchronously Iterable - 2021-03-31
• Lexicographical String Comparison - 2021-03-31
• Pump Large (> 2^53) Numbers Through Your Data Pipeline to Check for Leaks - 2021-03-31
• JavaScript RegExp Objects are Stateful - 2022-01-12
• Object.is is Different From === and !== - 2022-01-13
• in Operator Patterns are Rare - 2023-03-02
• HTML Comment Syntax in JavaScript - 2025-06-12

language-features

• Avoiding Nil - 2021-07-19

macos

• Perform Search Engine Queries from Spotlight - 2020-08-08
• Reveal . Files in Finder - 2024-08-24
• Modifier Keys in Menu Bar - 2024-08-24
• Instruments - 2024-08-30

node

• libuv Implements a Reactor Pattern - 2021-03-31
• Basic Node Test Runner - 2022-01-11

patterns

• Lazy-Iteration Over Multiple Sorted Enumerables, Preserving Order - 2024-08-21
• uv run in the Shebang Line - 2024-08-21
• Thunks for Delayed Computation and Dependency Injection - 2025-06-11
• Avoid Boolean Flag Arguments - 2025-06-12

posix

• The Difference Between Ctrl+c and Ctrl+\ - 2020-08-26

postgres

• Write a Query Result to a File - 2020-07-28
• Export Text Without Headers and Formatting - 2020-07-28
• Drop a Database Even When Clients are Connected - 2020-10-17
• psql Notes - 2024-08-17
• Postgres DiskFull Error - 2024-08-17
• Idenfity NULL JSON Values - 2024-08-27
• Cross-Table Row Deletions - 2024-08-29
• Materialized Views Require Their Own Indexes - 2025-05-28
• Parallel Queries Can Silently Downgrade to Serial Execution - 2025-05-28
• Use Real Database Fixtures Instead of Mocks - 2025-06-11
• When ALTER TABLE Requires a Rewrite - 2025-06-12
• Fixing Duplicate Primary Key Rows - 2025-06-12
• pg_input_is_valid for Data Type Validation - 2025-06-12
• Handle Zero Byte and Invalid UTF-8 Before Insert - 2025-07-10
• Postgres clocks for time consistency - 2025-07-13
• UUID v7 Monotonic Per Backend - 2025-07-13

python

• Creating Deep Copies of Collections - 2023-11-10
• Python dict.update method returns None - 2024-02-23
• JSON Encoding and Decoding I/O Conversions - 2024-02-23
• Python Development Environment Management (macOS) - 2024-08-11
• Eager and Lazy Evaluation - 2024-08-30
• uvtrick: Run Python Code from venv in Current Environment - 2024-09-02
• Typing Overloads - 2025-05-19
• Metaclasses - 2025-05-20
• Quiet Mode - 2025-05-21
• Format Mini-Language in f-strings - 2025-05-23
• Create Dual-Purpose Attributes with Proxy Properties - 2025-05-28
• Python's Futures - 2025-05-28
• Python's Triple-Quoted Strings Preserve Indentation - 2025-05-28
• Python's help() Function Features - 2025-06-12
• Reinstall Python Versions with uv - 2025-07-10
• Dump pickle files to readable text - 2025-07-12
• Template Strings for Safe Processing - 2025-07-13

regex

• Use Quine Quotes to Delimit Regular Expressions - 2022-01-10
• Character Classes Are a Sub-language of Regex - 2024-09-05
• Use Verbose Mode and Named Groups for Readable Patterns - 2025-07-09

ruby

• Run rbenv rehash to Use Newly Installed Versions of Ruby or Gems - 2020-07-03
• Skip Installing Ruby Docs - 2020-07-03
• Specify a Gem Version Range - 2020-07-03
• Reset Bundle Gems - 2020-07-30
• Numeric Literal Prefixes - 2020-08-02

sed

• Explicit Addressing - 2025-05-23

unix

• Look Up DNS with host - 2020-07-29
• Suppress File Names When Grepping Across Multiple Files - 2020-08-05
• wc -l is Faster than wc For Retrieving the Number of Lines in a Large File - 2020-08-06
• Reset Terminal Password Prompt - 2020-08-13
• Use the -i flag to Confirm Before Overwriting an Existing File - 2020-10-20
• Use column to View Pretty CSVs - 2020-10-31
• kill Works on Any Process - 2021-06-27
• Join CSV files with xsv - 2025-07-11
• Random sampling with shuf - 2025-07-11

vscode

• Navigate Your Cursor Position History - 2020-05-20
• Disable Jest Test Runner Auto Run - 2020-07-20
• Choose Folders to Ignore During Search - 2020-08-29

Development Setup

This project uses uv as its build system and package manager for fast, modern Python development.

Quick Start

# Install uv (if you haven't already)
curl -LsSf https://astral.sh/uv/install.sh | sh

# Clone the repository
git clone https://github.com/jthodge/til.git
cd til

# Setup development environment
uv venv
uv sync --all-extras

# Or use the helper script
./scripts/dev.sh init

Common Commands

# Build the database
uv run til build

# Update README
uv run til update-readme --rewrite

# Run Datasette locally
uv run datasette . -h 0.0.0.0 -p 8765 --cors

# Run tests
uv run pytest tests/

# Format and lint code
uv run ruff format til/ tests/
uv run ruff check til/ tests/

# Type check
uv run mypy til/

About

I shamelessly stole this idea from jbranchaud/til. And I hope you'll shamelessly steal it from me!

Other TIL Collections

• Today I Learned by Hashrocket
• Stefan Judis
• jwworth/til
• thoughtbot/til
• jbranchaud/til
• simonw/til
• jessesquires/TIL
• leebyron/til

License

© 2020 Taylor Hodge

This repository is licensed under the MIT license. See LICENSE for details.