You don't have write permissions for the /Library/Ruby/Gems/2.3.0 directory

Question

When I use command gem install bundler in MacOS 10.13.x, the error is:

You don't have write permissions for the /Library/Ruby/Gems/2.3.0 directory.

$ gem install bundler
Fetching: bundler-1.16.2.gem (100%)
ERROR:  While executing gem ... (Gem::FilePermissionError)
You don't have write permissions for the /Library/Ruby/Gems/2.3.0 directory.

Answer 1

This is basically a duplicate of this question, where I already posted a detailed answer that solves the problem. Instead of maintaining two separate answers, I thought it would be better to just link to my answer here since the same solution applies: https://stackoverflow.com/a/54873916/928191

Answer 2

As previously noted, on a Mac the system ruby is owned by root and it's not safe to install things against that version with sudo. If you do every gem runs as root and that's a security nightmare. DO NOT DO THAT

I'll walk you through my steps since previous answers assume a bit of command line foo and the added details might be of some use to someone.

Double-check we're running the old, system provided ruby

which ruby
/usr/bin/ruby

(that's the system path)

ruby -v
ruby 2.3.7

(the old version)

brew install ruby

or install brew first

at the end of which, the install says:

/usr/local/Cellar/ruby/2.6.3

Make that show up in the path first

PATH=/usr/local/Cellar/ruby/2.6.3/bin:$PATH

Double-check

which ruby
/usr/local/Cellar/ruby/2.6.3/bin/ruby

Double-check version

ruby --version
ruby 2.6.3p62

Make the path update permanent (otherwise you'll have to update the path each time you want to use ruby)

echo  PATH=/usr/local/Cellar/ruby/2.6.3/bin:$PATH >> ~/.bash_profile

Answer 3

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