How to make brew installed software take effect over the manually installed one? I have an older version of software that I once manually installed through installation package (version 0.6.6 -- I write it down here for later discussion purpose, but the version number is not relevant to this question).

Now I found brew is better why to manage the update/upgrade etc. So, I use brew to install the software by doing brew install terraform (version 0.6.9 -- again, I write it down here for later discussion purpose, but the version number is not relevant to this question), which is all good so far.

However, when I do terraform version to query the current effective version, I found it's still the old version.

My question is how I can make the brew installed software take over.

A side question is that which I try to find out terraform's location, by run which terra (hit tab now), which I normally do for other software, the tab won't do the auto complete action for me. Why is that?
The easiest solution would be to simply delete the old version of the software.

If you want to keep both, you'll need to change your $PATH environment variable so that the location of the new version appears before the location of the old version. Do this by editing ~/.bash_profile.