Homebrew: Could not symlink, /usr/local/share/man/man7 is not writable

Question

I'm installing LightGBM on OSX, following the installation guide. While installing cmake, Homebrew gives such warning message:

Warning: cmake-3.8.1 already installed, it's just not linked.

Then I try:

$brew link cmake

it gives:

Linking /usr/local/Cellar/cmake/3.8.1...
Error: Could not symlink share/man/man7/cmake-buildsystem.7
/usr/local/share/man/man7 is not writable.

Answer 1

The proposition of Mark Setchell to use sudo chown -R $(whoami):admin /usr/local/share/man is right. According to the Homebrew troubleshooting page:

If commands fail with permissions errors, check the permissions of /usr/local’s subdirectories. If you’re unsure what to do, you can run cd /usr/local && sudo chown -R $(whoami) bin etc include lib sbin share var Frameworks

but the proposition of Nano to use sudo is not a good one. According to the Homebrew FAQ:

Homebrew is designed to work without using sudo. You can decide to use it but we strongly recommend not to do so. If you have used sudo and run into a bug then this is likely to be the cause. Please don’t file a bug report unless you can reproduce it after reinstalling Homebrew from scratch without using sudo.

Answer 2

Just follow these 4 steps

1. sudo chown -R $(whoami) $(brew --prefix)/*
2. brew doctor
3. brew prune
4. brew link cmake