How can I brew link a specific version?

Question

I have a few kegs of the same package in /usr/local/Cellar/libfoo like /usr/local/Cellar/libfoo/1.0.1, /usr/local/Cellar/libfoo/HEAD a

Answer 1

The usage info:

Usage: brew switch  

Example:

brew switch mysql 5.5.29

You can find the versions installed on your system with info.

brew info mysql

And to see the available versions to install, you can provide a dud version number, as brew will helpfully respond with the available version numbers:

brew switch mysql 0

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Update (15.10.2014):

The brew versions command has been removed from brew, but, if you do wish to use this command first run brew tap homebrew/boneyard.

The recommended way to install an old version is to install from the homebrew/versions repo as follows:

$ brew tap homebrew/versions
$ brew install mysql55

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For detailed info on all the ways to install an older version of a formula read this answer.