777 permissions aren't necessarily bad here – you'll probably never run into permissions problems, and it's not a huge security issue I'd say.
Anyway, the "normal" permissions on /usr/local/share that Homebrew requires should be (recursively) 755, thus rwxr-xr-x.
chmod -R 755 /usr/local/share
At least brew shouldn't need sudo permissions to ever do anything in there. Only /usr/local is owned by root, but writable for the staff group, in which your user should be in.
For fixing existing Homebrew installations, check out this gist, which is a script that will attempt to correct your /usr/local permissions.
As an example, here's the directory listing of one of my (sane) Homebrew installations with ghostscript being the only exception that needed a sudo brew link:
aeneas:local werner$ ls -la /usr/local/share/
total 40
drwxr-xr-x 11 werner staff 374 Mar 5 14:53 .
drwxrwxr-x 14 werner staff 476 Feb 28 12:51 ..
drwxr-xr-x 6 werner staff 204 Mar 5 14:54 aclocal
drwxr-xr-x 8 werner staff 272 Mar 5 14:53 doc
lrwxr-xr-x 1 werner staff 34 Feb 8 12:26 ffmpeg -> ../Cellar/ffmpeg/0.10/share/ffmpeg
drwxr-xr-x 4 werner wheel 136 Apr 16 2010 ghostscript
lrwxr-xr-x 1 werner staff 36 Mar 5 14:53 git-core -> ../Cellar/git/1.7.9.2/share/git-core
lrwxr-xr-x 1 werner staff 35 Mar 5 14:53 git-gui -> ../Cellar/git/1.7.9.2/share/git-gui
lrwxr-xr-x 1 werner staff 32 Mar 5 14:53 gitk -> ../Cellar/git/1.7.9.2/share/gitk
lrwxr-xr-x 1 werner staff 34 Mar 5 14:53 gitweb -> ../Cellar/git/1.7.9.2/share/gitweb
drwxr-xr-x 9 werner staff 306 Mar 5 14:53 man
Obviously that folder doesn't belong to you. Just try with:
sudo chown -R $(whoami) /usr/local/include
You never have to use brew with sudo. If you do, something is wrong with your installation.
Then, try the link command again.
Best Answer
You do not need
sudofor HomebrewRun:
Homebrew never needs elevated privileges for anything – except for when there are some conflicts with other installed libraries:
If you can't install it without
sudo, make sure you own/usr/localand have the correct permissions – also by running this script. Runningbrew doctorwill also generally give you some good hints.