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TIL

Today I Learned

Inspired by jbranchaud/til.

AWS

List Stacks

aws cloudformation list-stacks --profile <profile-name-optional> | jq '.StackSummaries | .[] |  {name: .StackName, status: .StackStatus}'

Delete Stack

aws cloudformation delete-stack --stack-name place-indexer --profile <profile-name-optional>

conda

Quick howto on installing and using the conda package manager.

brew install miniconda

Add to your shell:

conda init zsh

Create a new environment with a specific Python version:

conda create -n notebooks python=3.9

List available environments:

conda env list

Remove an environment:

conda env remove --name notebooks

Install a package to the current environment:

conda install jupyterlab=3

fzf

Pipe any list output to fzf and get an interactive fuzzy selector.

List recent Git branches and switch to one

This works as a shell function. Add it to your .zshrc file.

fbr() {
  local branches branch
  branches=$(git branch --all | grep -v HEAD) &&
  branch=$(echo "$branches" |
           fzf-tmux -d $(( 2 + $(wc -l <<< "$branches") )) +m) &&
  git checkout $(echo "$branch" | sed "s/.* //" | sed "s#remotes/[^/]*/##")
}

As seen in fzf/wiki

Git

List TODOs in the current branch

git diff master..$(git branch --show-current) | grep TODO

Switch to main as the default branch

Set main as default branch:

git config --global init.defaultBranch main

Continue reading if you have older repos that need updating.

For older repos, update default branch:

git checkout -b main
git push -u origin main

On GitHub, you need to update the default too:

  1. Go to the repo settings
  2. Go to Branches
  3. In the Default branch section, click the Switch to another branch button
  4. Choose main and update

Add only tracked files

git add --update

Shorthand:

git add -u

gh

List my repos

gh repo list

Create PR with a title

gh pr create --title "The PR title"

Generate PR title from the branch name

If you use PROJ-XXX-slug pattern for your branch names, and use PROJ-XXX: slug for your PR title, you can do a little string munging with $(git branch --show-current) and have the PR title generated from the branch name.

# insert bash one liner here

Clone all repos of a GitHub user/organization

Sometimes you want to clone all the repos from an organization. You can do this using gh, jq and xargs.

Here <username> can be a GitHub user or organization.

gh repo list <username> --json nameWithOwner --jq ".[] | .nameWithOwner" | xargs -I REPO gh repo clone REPO -- REPO

Be aware that this may copy hundreds of repos to your machine, so you might want to check how many repos the user have with gh repo list <username> first.

Use -L or --limit to specify the number of repos to clone.

Go

install go

brew install go

go get installs where?

I can "get" a module like this:

go get github.com/user/repo

But where is it installed?

It's in ~/go/bin/.

Jupyter Lab

Save cell contents as file

Using %%file magic function, the cell contents will be saved in the specified file. For example:

%%file my_script.py
print('hello.py')

After executing the cell, you should see Writing my_script.py as the cell output, and a new file is created with the contents print('hello.py')\n

Code formatting

Install jupyter_code_formatter extension. This adds a code format button in the notebook toolbar, and two new commands in the Edit menu.

Make sure you have black and isort installed.

pip install jupyterlab_code_formatter
pip install black isort

Kubernetes

Working with contexts

List available contexts:

kubectl config get-contexts

Show current context:

kubectl config current-context

Change context:

kubectl config use-context <context name>

pandas

Read from newline delimited JSON file

pd.read_json(filepath, lines=True)

pyenv

List installable Python versions

pyenv install --list

List installed Python versions

pyenv versions

Set Python version

pyenv global 3.9.0

Set local Python version

When you want to set a Python version for a single workspace.

pyenv local 3.7.9

Rust

cargo

open docs locally

This will generate HTML docs of the current crate and its dependencies, and open it in the browser.

cargo doc --open

cargo addons

Extends cargo to have commands such as cargo add, making Cargo.toml management a breeze.

rustup

install nightly toolchain

rustup toolchain install nightly

list installed toolchains

rustup toolchain list

set default toolchain

rustup default <toolchain name>

# use nightly
rustup default nightly

# back to stable
rustup default stable

update toolchain

rustup update

This will update the everything included in the toolchain, such as rustc, cargo, rustfmt.

update rustup itself

rustup self update

open rust bookshelf

Opens local copy of Rust documentation, including The Rust Programming Language.

rustup doc

shell

Access the most recent parameter

$_

For example, create a directory and change into it:

mkdir /tmp/mydir && cd $_

Get my computer's MAC addresses

ifconfig | grep ether | awk '{print $2}'

Operate on files with names starting with hyphen

When filenames start with a hyphen and commands may interpret it as argument.

For example, you have a file called -test and want to rename this to test. This won't work:

mv -test test
mv: illegal option -- t
usage: mv [-f | -i | -n] [-v] source target
       mv [-f | -i | -n] [-v] source ... directory

Use the -- signal to end option processing before typing the filename.

mv -- -test test

This works with other commands as expected:

touch -- -myfile
rm -- -myfile

imagemagick

Friendly reminder: imagemagick commands may contain hidden magic and can be destructive -- be sure to backup and work on the copy of your precious images.

Combine images side by side

montage -geometry 500x500 [input-file1 input-file2...] output-file

Rotate an image 90 degrees

convert -rotate "90" original.gif rotated-output.gif

Convert an image format

This will create a copy of the image with a new format:

convert input.heic output.jpg

Convert format of multiple files

If you have a bunch of HEIC files and want to convert all of them to JPG:

mogrify -format jpg *.heic

exiftool

Remove EXIF metadata from photos

This will remove all metadata from the given photo file.

exiftool -all= photo.jpg

Here the photo.jpg will be stripped of the metadata, and a copy of the original will be created. To overwrite the original without preserving a copy, use the -overwrite_original option.

VS Code

Useful navigation shortcuts

  • Find file by name: cmd + p
  • Go to symbol in the currently open file: cmd + shift + o
  • Go to symbol: cmd + t

Enable code-insiders command for the Insiders version

Within the editor, open command executor with cmd+shift+p and type "Install code-insiders command in PATH" and execute it.

List installed extensions

code --list-extensions

Run selection/current line in Python REPL

Tap shift+enter. This will open a Python repl and execute the selected code.

This is also available via the command view (cmd+shift+p). Open the command view and type "python run line" (partial input works).

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