Mac sudo chown -R $(whoami) /usr

Error: The following directories are not writable by your user:
/usr/local/share/man/man5

You should change the ownership of these directories to your user.
  sudo chown -R $(whoami) /usr/local/share/man/man5

And make sure that your user has write permission.
  chmod u+w /usr/local/share/man/man5

这里我们按提示使用sudo chown -R $(whoami) /usr/local/share/man/man5，
先输入：

who am i

再把上面那个$(whoami)替换为yuanhust，改变dir的owner

sudo chown -R yuanhust /usr/local/share/man/man5

然后添加user的write permission

chmod u+w /usr/local/share/man/man5