git hook for a common use case: linting staged files before commit. Pipes all staged JS or TS files to eslint, and all CSS or SCSS files to stylelint. Assuming eslint and stylelint are node modules installed in the same root as the git repo.

pre-commit

#!/usr/bin/env bash

root="$(git rev-parse --show-toplevel)" # Full file path to the directory where this git repo sits
cd "$root" # Required to make the relative file paths to eslint and stylelint work

for file in $(git diff --name-only --cached) # List of staged files
do

  filename="${file##*/}" # Remove all except the characters after the last '/'
  extension="${filename##*.}" # Remove all except the characters after the last '.'

  if [[ "$extension" =~ ^(js|ts)$ ]]; then
    # Must pipe the output from 'git show' to the linter, do NOT directly run the linter
    # on the file because that may contain changes that have been saved but not staged yet.
    git show ":$file" | ./node_modules/.bin/eslint --stdin --stdin-filename "$filename"
    if [ $? -ne 0 ]; then
      echo "eslint failed on ${file}, aborting commit."
      exit 1
    fi
  fi

  if [[ "$extension" =~ ^(css|scss)$ ]]; then
    # Must pipe the output from 'git show' to the linter, do NOT directly run the linter
    # on the file because that may contain changes that have been saved but not staged yet.
    git show ":$file" | ./node_modules/.bin/stylelint --stdin --stdin-filename "$filename"
    if [ $? -ne 0 ]; then
      echo "stylelint failed on ${file}, aborting commit."
      exit 1
    fi
  fi

done