有時候使用Homebrew安裝應用的時候會出現：
Error: The following directories are not writable by your user:
/usr/local/share/man/man8
You should change the ownership of these directories to your user.
sudo chown -R $(whoami) /usr/local/share/man/man8
這是權限問題導致的，解決方式是收回權限，就可以正常的安裝下載：
sudo chown -R `whoami`:admin /usr/local/bin
sudo chown -R `whoami`:admin /usr/local/share