mac安装brew
一，安装brew
1，安装brew
curl -LsSf http://github.com/mxcl/homebrew/tarball/master | sudo tar xvz -C/usr/local --strip 1
2，安装完成后执行
brew
提示：Please run brew update!
3，按照提示更新，执行
brew update
报错：Error: /usr/local must be writable!
4，赋给/usr/local目录权限，执行sudo chown -R $(whoami) /usr/local，即
报错：Operation not permitted
发现是El Capitan（10.11） 加入了Rootless机制，很多系统目录不再能够随心所欲的读写了，即使设置 root 权限也不行。
以下路径无法写和执行
/System
/bin
/sbin
/usr (except /usr/local)- 1
- 2
- 3
- 4
需要关闭rootless
如何关闭
重启按住 Command+R，进入恢复模式，打开Terminal
csrutil disable- 1
sudo chown -R caositing /usr/local
其中caositing为系统当前用户名。
5，再次执行
brew update
提示：
remote: Total 0 (delta 0), reused 0 (delta 0), pack-reused 0
HEAD is now at c3f959d Merge pull request #1542 from woodruffw/deprecate-utils-json
To restore the stashed changes to /usr/local run:
'cd /usr/local && git stash pop'
==> Homebrew has enabled anonymous aggregate user behaviour analytics
Read the analytics documentation (and how to opt-out) here:
https://git.io/brew-analytics
==> Tapping homebrew/core
Cloning into '/usr/local/Library/Taps/homebrew/homebrew-core'...
remote: Counting objects: 3757, done.
remote: Compressing objects: 100% (3647/3647), done.
remote: Total 3757 (delta 13), reused 305 (delta 1), pack-reused 0
Receiving objects: 100% (3757/3757), 3.00 MiB | 30.00 KiB/s, done.
Resolving deltas: 100% (13/13), done.
Checking connectivity... done.
Tapped 3636 formulae (3,784 files, 9.3M)
Already up-to-date.
Error: Could not link:
/usr/local/share/doc/homebrew
Please delete these paths and run `brew update`.
==> Migrating HOMEBREW_REPOSITORY (please wait)...
Error: Could not link:
/usr/local/share/doc/homebrew
Please delete these paths and run `brew update`.
==> Migrated HOMEBREW_REPOSITORY to /usr/local/Homebrew!
Homebrew no longer needs to have ownership of /usr/local. If you wish you can
return /usr/local to its default ownership with:
sudo chown root:wheel /usr/local
6，按照提示删除/usr/local/share/doc/homebrew，执行
rm -r -f /usr/local/share/doc/homebrew
7，再次执行
brew update
安装更新成功！