Macos Catalina error after update: unable to run colorls

This worked for me:

xcode-select --install sudo gem install colorls -n /usr/local/bin

Here is how I solved it:

1. sudo xcode-select --install
2. Install rbenv with brew install rbenv
3. Add eval "$(rbenv init -)" to the end of ~/.zshrc or ~/.bash_profile
4. Install a ruby version rbenv install 2.6.0
5. Select a ruby version by rbenv rbenv global 2.6.0
6. Open a new terminal window.
7. Verify that the right gem folder is being used with gem env home (this should report something in your user folder, not system wide).

After this I installed colorls again using sudo gem install colorls

If getting error:

ERROR:  While executing gem ... (Gem::FilePermissionError)
    You don't have write permissions for the /usr/bin directory.

Try installing colorls using cmd:

sudo gem install colorls -n /usr/local/bin

After this you see colorls is installed successfully and new terminal works fine.

This fixed for me:

$ sudo gem update
$ sudo gem install colorls

Catalina now ships with Ruby 2.6, instead of 2.3. My guess is that with the upgrade, all custom installed gems became "untracked" by the new Ruby/Gem package system. With that, gem update doesn't take care of updating colorls.

Make sure you reinstall XCode command line tools, update/upgrade brew, npm and others.