Install icu4c version 63 with Homebrew

Solution:

1. cd to Homebrew's formula directory

• Intel

  cd $(brew --prefix)/Homebrew/Library/Taps/homebrew/homebrew-core/Formula

• M1

  cd $(brew --prefix)/Library/Taps/homebrew/homebrew-core/Formula

2. Find desired commit (version 63 for icu4c) to checkout

git log --follow icu4c.rb

3. Checkout to a new branch

git checkout -b icu4c-63 e7f0f10dc63b1dc1061d475f1a61d01b70ef2cb7

4. Reinstall the library with the new version

brew reinstall ./icu4c.rb

5. Switch to the reinstalled version

brew switch icu4c 63.1

6. Checkout back to master

git checkout master

Sources:

• Homebrew install specific version of formula?
• http://hanxue-it.blogspot.com/2018/08/macos-homebrew-installing-older-version-of-software.html

Bonus for those who ended up using this more than once:

# zshfunction hiicu63() {  local last_dir=$(pwd)  cd $(brew --prefix)/Homebrew/Library/Taps/homebrew/homebrew-core/Formula  git checkout icu4c-63  brew reinstall ./icu4c.rb  brew switch icu4c 63.1  git checkout master  cd $last_dir}

Like @dingusjh says, but use reinstall command instead of install in case brew complains about having icu4c installed already and you should try to extract. The complete command would then be:

brew reinstall https://raw.githubusercontent.com/Homebrew/homebrew-core/e7f0f10dc63b1dc1061d475f1a61d01b70ef2cb7/Formula/icu4c.rb

This should be easier.

brew install https://raw.githubusercontent.com/Homebrew/homebrew-core/e7f0f10dc63b1dc1061d475f1a61d01b70ef2cb7/Formula/icu4c.rb