Getting a "bad interpreter" error when using brew

Fix:

sudo gem install cocoapods

What you are getting means that Homebrew has not been able to locate the Ruby interpretter at the specified location.

Install Apple Developer Kit (comes with Xcode) which should be available to you as an optional install (or you can simply download it from Apple). This will install the Ruby interpreter for you.

In case you already have Xcode installed, this means that one of these things is happening:

1. You have a broken Ruby installation
2. You have more than one Ruby installation
3. Your installation has not been configured properly.

To identify if this is the first case, you can run ruby and see if you get any response.

If you don't, your installation is broken and you need to reinstall it. If you do, you then run which ruby. This should give you the absolute path to your Ruby executable. If this is anything other than /usr/bin/ruby then homebrew (and a bunch of other programs) will not be able to find it.

In case you have not ever tampered with your Ruby installation, you can check to see if /usr/bin/ruby already exists or not: cat /usr/bin/ruby. If you get No such file or directory, then you can easily create a symbolic link to your Ruby installation. Assuming the output of which ruby to by /usr/local/bin/ruby, you create the symbolic link this way: sudo ln -s /usr/local/bin/ruby /usr/bin/ruby and all should be well.

If there is a file at that location, you can run file /usr/bin/ruby to see if it's a real file, a symbolic link, or a corrupted file. If it is a symbolic link, your installation should be working, and since it's not, it probably is either a corrupted symlink or it's a bogus file.

You can remedy that by first deleting it (sudo rm /usr/bin/ruby) and then creating a new symlink to the correct location (sudo ln -s /usr/local/bin/ruby /usr/bin/ruby).

If non of the above works, you should consult the homebrew team after a clean install of Xcode and removing any traces of a Ruby installation on your system.

EDIT

Alternatively, as pointed out by the other answers, the issue might be because of a bad ruby version in your Homebrew settings.

A quick fix might be updating your Homebrew:

cd /usr/local
git pull -q origin refs/heads/master:refs/remotes/origin/master

If this does not help, you might want to get your hands dirty and manually fix the problem by:

1. Editing brew.rb from /user/local/Library/brew.rb
2. Changing /1.8/ to /Current/ in the first line, which will cause the hashbang to point to the current Ruby version as the executor

If this does not help, either, you can also modify the MACOS check and change it from 10.5 to 10 to avoid the infamous "Homebrew requires Leopard or higher" error.

DISCLAIMER

A bunch of thanks to other contributors in the answers below and their commenters. I am not committing plagiarism, simply aggregating the answers into one integrated article to help others.

I got this error (much the same):

/usr/local/bin/brew: /usr/local/Library/brew.rb: /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby: bad interpreter: No such file or directory /usr/local/bin/brew: line 26: /usr/local/Library/brew.rb: Undefined error: 0

and fixed by the solution below:

1. Open brew.rb:

   $ sudo vim /usr/local/Library/brew.rb
   

2. Change the first line's 1.8 to Current:

   Before:

   #!/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby -W0
   

   After:

   #!/System/Library/Frameworks/Ruby.framework/Versions/Current/usr/bin/ruby -W0
   

Then brew works for me. Hope it helps if any other one got this issue. :)

---

If you get the error

Homebrew requires Leopard or higher. For Tiger support, see: https://github.com/mistydemeo/tigerbrew

change the MACOS check from <10.5 to <10.

Tip by @TimCastelijns:

10.5 doesn't work because in comparison, it's higher than 10.10 (.1 vs .5). I added a check (and MACOS_VERSION != 10.10) instead of lowering from 10.5 to 10.