Useful code snippets

1 May 2015

I'm going to use this post to keep all the useful things about Git in particular but other things as well.

Add new remote repository

git remote add origin <remote repository URL>

Create a new branch to work in

git checkout -b <branchname>

Merge branch back in

• git checkout master
• git pull origin master
• git merge <branchname> --no-ff
• git push origin master

Update gh-pages with master

• git checkout gh-pages
• git merge master
• git push origin gh-pages

Create Github page branch

• git checkout -b gh-pages
• git commit -m "First commit to gh-pages branch"
• git push origin gh-pages

Discard unstaged changes

• git clean -df
• git checkout -- .

Remove files from the repository based on your .gitignore without deleting them from the local file system

git rm --cached 'git ls-files -i -X .gitignore'

Remove file/folder from Git repository without deleting it from the local filesystem

• git rm --cached mylogfile.log
• git rm --cached -r mydirectory
• git rm --cached -r platforms
• git rm -r --cached some-directory

Remove node_modules

• add ‘node_modules’ to .gitignore file
• git rm -r --cached node_modules
• git commit -m 'Remove the now ignored directory node_modules'
• git push origin master

Roll back to previous commit

git revert --no-commit 544993f8416a6e8a0cde66f7ea28379f9ebf446c .HEAD

This will revert everything from the HEAD back to the commit hash. (The –no-commit flag lets git revert all the commits at once, instead of littering history with messages for each commit in the range.)

to discard all the changes, and get a clean working tree:

• git reset --hard HEAD
• git revert --continue

See history of commits

git log

See remote branches

git remote show origin

Update gh-pages branch with master

git push origin master:gh-pages

New gh-pages branch and publish

• git checkout -b gh-pages
• git push origin gh-pages

Keep gh-pages up to date with a master branch

• git add .
• git status // to see what changes are going to be commited
• git commit -m ‘Some descriptive commit message’
• git push origin master
• git checkout gh-pages // go to the gh-pages branch
• git rebase master // bring gh-pages up to date with master
• git push origin gh-pages // commit the changes
• git checkout master // return to the master branch

Kill processes

• $ top
• $ kill -9 PID, e.g. $ kill -9 93799

Start a webserver - cd into directory and:

• python -m SimpleHTTPServer 8888 & // Go to http://localhost:8888/
• python3 -m http.server // For Python 3:

Open bash profile in textedit

1. touch ~/.bash_profile; open ~/.bash_profile
2. source ~/.bash_profile

See what’s on the path

echo $PATH

Copy gem sets

rvm allows you to have many different installations of ruby. You can copy gem sets across

• rvm gem set copy old new
• rvm gem set copy 2.0.0-p353 2.1.3

Ruby versions and sudo

• rvm list
• rvm use RUBY-VERSION
• rvm gemset list
• gem install GEM --no-document

Homebrew

• brew info <package>
• brew switch node 0.12.7_1
• brew switch node 4.1.1

Homebrew housekeeping

• brew autoremove - Removes formula only installed as a dependency of another formula and are now no longer needed.
• brew cleanup - Removes downloads for outdated formulas and casks.

Homebrew updating

• brew upgrade - Get the latest versions of packages.
• brew upgrade FORUMLA - Get the latest versions of a specific packages.

Homebrew permissions

• sudo chown -R $(whoami) /usr/local

Python versions using pyenv

Reference

• pyenv install 2.7.7
• pyenv versions
• pyenv global 2.7.7
• pyenv local 3.4.0
• pyenv virtualenvs
• pyenv virtualenv 2.7.7 my_project
• pyenv activate my_project
• pyenv deactivate
• pyenv shell Cellar - sets to Homebrew Python
• Use pyenv shell system when installing something relating to python via brew

Python checks

• python-config --prefix
• which python
• pyenv which python
• brew --prefix
• echo $PYTHONPATH

Python and Homebrew

• Only brew install while pyenv global is set to system and never brew while in a virtual environment. pyenv global system Reference
• To fix brew doctor issue try echo 'alias brew="env PATH=${PATH//$(pyenv root)\/shims:/} brew"' >> .bash_profile or echo 'alias brew="env PATH=${PATH/\/Users\/roberto\/\.pyenv\/shims:/} brew"' >> .bash_profile

Use pyenv and virtualenv

Virtualenv lets you create isolated Python environments where you can pin down versions of site-packages specific to a particular project. $ pip install virtualenv $ pyenv install 2.7.2 $ pyenv shell 2.7.2 $ virtualenv which python foo $ source foo/bin/activate $ pip install pandas $ pip install numpy

Get rid of new mail (bouncebacks) in Terminal

• mail
• delete 1- where 1- is the number of message, ie message 1 or 2 etc
• q

List globally installed NPM packages and version

• “global installs are for command-line applications. Local installs are for things you require().”
• npm list -g --depth=0
• On npm and homebrew

nvm and node

• Note: As of 2016 I am using https://github.com/tj/n for Node version stuff.
• nvm alias default node set alias to node itself to avoid updating the default alias along with node version updates later on.
• nvm alias default version, eg nvm alias default 0.12.7 sets the default node version in your shell. Then verify that the change persists by closing the shell window, opening a new one, then: node –version.
• If you want to update to latest stable version (lts - recommended for most users), then you should run: nvm install lts/* –reinstall-packages-from=node. After that you can cleanup your versions with nvm uninstall [old version]. You can list all installed versions with nvm ls

Smart quotes

• Single opening - alt + ]
• Single closing & apostrophe - alt + shift + ]
• Double opening - alt + [
• Double closing - alt + shift + [
• See Smart Quotes for details.

Merging topojson

When combining two or more files, you can specify the properties to keep:

• topojson -o select.json -p sov0name,name -- subunits.json places.json

Batch crop using Imagemagick

Quick batch crop:

• mogrify -crop x_sizexy_size+x_offset+y_offset inputfile outputfile Make a new folder called ‘cropped’ to keep the cropped images in.
• mogrify -crop 300x300+150+150 -path ./cropped *.jpg

Resize using Imagemagick

• mogrify -resize 640x427 -path ./cropped *.jpg

Convert to gif using Imagemagick

• convert -delay 100 -loop 0 input*.jpg animation.gif

Regex to replace content between two characters

• (?s)START(.*?)END’ as in ’(?s)<table(.*?)</table>

Regex to replace content between two characters

• First brew install rename
• Then for dry run rename -n 'y/A-Z/a-z/ | s/\s+//g' *.jpg
• And remove -n to do it: rename 'y/A-Z/a-z/ | s/\s+//g' *.jpg

• First one is lowercase and second is white space linked together by pipe (

  ) and this will do all jpgs in a folder.

• Note Macs are not case sensitive with filenames so just doing the lowercase won’t work on its own.

Regex to turn change case on text between two characters

• Using Sublime Text - Make sure case sensitivity is on (Alt + C) and preserve case is off (Alt + A).
• "name": "([a-zA-Z0-9_ ]*+)"
• The brackets create capture group. You can create more than one capture group. You reference it using $n, where n is the number of the capture group.
• "name": "\U$1" so $1 gets everything between the brackets
• \u capitalises words and \l uncapitalises words. There’s loads more options
• This is quite a good article: https://codepen.io/jakealbaugh/post/regex-in-sublime-text

Print a list of filenames from a folder

• ls ./ > output.txt

PDF to text

• pdftotext -layout -enc UTF-8 inputfilename.pdf outputfilename.md

Keyboard shortcuts

• On a Mac: System Prefs > Keyboard > Text is where you can create shortcuts for oft-used words and phrases
• System Prefs > Keyboard > Shortcuts

Importing photos from iPhone to computer

• Use either Image Capture or Preview
• Select all, move to a folder, then delete from device.
• Don’t use Photos or any other Apple thing because it stores them in a crazy format.

File path locations

• / = root of the current drive;
• ./ = current directory;
• ../ = parent of the current directory.

Fix for blocked camera in Skype

• Close Skype
• Terminal: sudo killall VDCAssistant
• See here for details

Kill Jekyll

• Jekyll serve went crazy and create huge files
• Kill it with pkill -f jekyll

Activate emoji keyboard

• Mac OS: control-command-space activates emoji keyboard

Export Github issues to CSV

• Open the following URL in a browser substituting the {owner} and {repo} with real values: https://api.github.com/repos/{owner}/{repo}/issues?page=1&per_page=100

Eject disk popup gets stuck

• Terminal: killall UnmountAssistantAgent

Rename a Github branch

git branch -m new_name

Bootstrap media queries

• screen-sm-max = screen-md-min - 1 = 992 - 1 = 991
• screen-xs-max is 767px
• screen-xs-max = screen-sm-min - 1 = 768 - 1 = 767

Optimise images with

convert puzzle.jpg -sampling-factor 4:2:0 -strip -quality 85 -interlace JPEG -colorspace RGB puzzle_converted.jpg

Mac shortcuts

• CMD + Shift + right arrow - select to end of the line
• Double click - select the entire word

Delete shapefile in QGIS

• right click the layer
• choose “Toggle Editing”
• in the toolbar select the pointer with the area “Select Features …”
• click on Antartica
• press delete on the keyboard

Find IP

• Open Terminal
• ping url

pyenv and homebrew

• https://amaral.northwestern.edu/blog/troubleshooting-pyenv
• Only brew install while pyenv global is set to system and never brew while in a virtual environment.
• $ brew uninstall that_thing_you_installed_wrong
• $ pyenv global system
• $ brew install that_thing_you_installed_wrong

Rename files in a folder

• brew install ren
• ren ‘*.txt’ ‘#1.md’

Download YouTube video as audio

$ youtube-dl --audio-format 'best' "URL" $ youtube-dl --audio-format 'm4a' URL

Convert webm to mp4

ffmpeg -i FILENAME.webm FILENAME.mp4

Extract the audio from an .WEBM movie file to an .MP3 audio file

FILE="the-file-you-want-to-process.webm"; ffmpeg -i "${FILE}" -vn -ab 128k -ar 44100 -y "${FILE%.webm}.mp3";

Batch process all WEBM video files in a folder

for FILE in *.webm; do echo -e "Processing video '\e[32m$FILE\e[0m'"; ffmpeg -i "${FILE}" -vn -ab 128k -ar 44100 -y "${FILE%.webm}.mp3"; done;

Batch process all MKV video files in a folder

for FILE in *.mkv; do echo -e "Processing video '\e[32m$FILE\e[0m'"; ffmpeg -i "${FILE}" -vn -ab 128k -ar 44100 -y "${FILE%.webm}.mp3"; done;

Batch process all mp4 video files in a folder

for i in *.mp4; do ffmpeg -i "$i" "${i%.*}.mp3"; done

Add to things

The email’s subject becomes your to-do’s title, and the rest goes into the notes.

MySQL

• To start the MySQL server, use the mysql.server tool: $ mysql.server start
• To stop it when you are done, run: $ mysql.server stop
• You can see the different commands available for mysql.server with: $ mysql.server –help
• To connect with the command-line client, run: $ mysql -uroot (Use exit to quit the MySQL shell.)

Note: By default, the MySQL user root has no password. It doesn’t really matter for a local development database. If you wish to change it though, you can use $ mysqladmin -u root password 'new-password'.

To start mongodb on Catalina

mongod --config /usr/local/etc/mongod.conf

Incorporate a separate repo into your repo

“There isn’t anything to compare. Nothing to compare, branches are entirely different commit histories” Starting from master:

• git branch new_branch
• git checkout new_branch

Free up space on Mac

• About my Mac > Storage > Manage

Capture video stream in VLC

• File > Open network
• Paste video url
• Settings
  • File > browse > “where to save file”
  • encapsulation method > MPEG 4
  • Open

Merge a folder of text files into a single file

cat *.txt » ~/Desktop/combined.txt

Force log in page on hotel wi-fi

• clear custom DNS
• incognito browser
• captive.apple.com

Uninstall npm

curl -qL https://www.npmjs.com/install.sh | sudo sh

Changing file extensions for all files in a directory

• Could brew install ren and then ren 'prefix_*.txt' 'prefix_#1.md'
• Or use Finder
• Select all the files, right-click and select “rename…”
• Add the existing file extension in “Find” and the extension you want to replace with “Replace with”.

VS Code tips

— Select all occurrences of find match

• Mac: cmd+shift+L