In terminal, input cmd: 

xcode-select --install

 to install command tool

Reference:http://cache.baiducontent.com/c?m=9d78d513d98910f20eba837e7c478a394607dc352bd7a14b2488c45f93151d1c1a38a2af60624e0b89833a2516ae3a41f7a0682f621420c0ca89de16cabbe57478ce3a75334d874017d41aaace5b768166cb0bb7f804b1edb661c8f093cedf5557ce53007d87&p=882a9543d6915ff9099fcc2d02148c&newp=c97dc30a90904ead46bd9b7e0b169e231610db2151ddd61161&user=baidu&fm=sc&query=xcode+command+line+tools&qid=af24e0330000e8a9&p1=1

Mac OX 10.8+ install cmd tool