更新:在Lion 10.7.4中，命令行工具已经在XCode中可用。你可以从App Store免费获得。

GCC for OSX不会编译从macports获得的一些包。 https://github.com/kennethreitz/osx-gcc-installer/downloads

Xcode Command Line Tools can be installed as a side effect of running git --version in Terminal without Git installed. You will be prompted to install the tools as a requirement for running Git. Apple ships a binary of git with the Command Line tools. This is confirmed on the Git for Mac Download page. This seems like a valid option considering that Homebrew requires the Command Line tools to install Git as well according to another SO post. Otherwise, the previous answers are the most direct methods of install the tools.

如果你想使用XCode本身提供的工具版本，你可以使用xcrun(例如xcrun git)。从下载首选项窗格底部的帮助:

注意，您可以在终端中使用XCRUN工具来启动 编译器和其他嵌入在Xcode应用程序中的工具。使用 Xcode - select工具定义激活的Xcode版本。 在终端内输入“man xcrun”以了解更多信息。

如果你在尝试使用命令行工具时查看“控制台”，你会发现实际上有一个到Mountain Lion命令行工具的“非官方”链接!

所以试试吧:

http://adcdownload.apple.com/ios/ios_simulator__resigned/cltools_mountainliondp2_march12.dmg

这是我的控制台日志:

01/04/2012 15:41:54.258 Xcode: [MT] DVTDownloadable: Download failed. Downloadable: {
    dependencies =     (
    );
    fileSize = 141452226;
    identifier = "Xcode.CLTools.10.8";
    name = "Command Line Tools";
    source = "http://adcdownload.apple.com/ios/ios_simulator__resigned/cltools_mountainliondp2_march12.dmg";
    userInfo =     {
        ActivationPredicate = "$MAC_OS_X_VERSION >= '10.8.0' && $MAC_OS_X_VERSION < '10.9.0'";
        InstallPrefix = "/";
        InstalledIfAllSHA1SumsMatch =         {
            "/usr/bin/clang" = 600c35175775a6002452a88f17e00c570cd2e2d0;
        };
        Summary = "Before installing, note that from within Terminal you can use the XCRUN tool to launch compilers and other tools embedded within the Xcode application. Use the XCODE-SELECT tool to define which version of Xcode is active.  Type \"man xcrun\" from within Terminal to find out more.\n\nDownloading this package will install copies of the core command line tools and system headers into system folders, including the LLVM compiler, linker, and build tools.";
        "Xcode.SDKs" =         (
        );
    };
    version = "1.1.1";
}. Error: Error Domain=NSCocoaErrorDomain Code=3840 "The data couldn’t be read because it has been corrupted." (Encountered unknown ampersand-escape sequence at line 18) UserInfo=0x401bc8e60 {NSDebugDescription=Encountered unknown ampersand-escape sequence at line 18, kCFPropertyListOldStyleParsingError=The data couldn’t be read because it has been corrupted.}

Xcode命令行工具可以从这里下载:https://developer.apple.com/downloads/index.action#

2014年4月版直接下载链接(适合想马上上手的开发人员) https://developer.apple.com/downloads/download.action?path=Developer_Tools/command_line_tools_os_x_mavericks_for_xcode__april_2014/command_line_tools_for_osx_mavericks_april_2014.dmg

如何获得安装在Xcode 4.4 / Mac OS X v10.8 (Mountain Lion)或更高版本的命令行构建工具?

对于OS X 10.9，你只需安装Xcode。命令行工具与Xcode捆绑在一起。技术说明TN2339，从命令行构建Xcode常见问题解答:

在OS X 10.9版本的Xcode中，无法下载命令行工具。如何在我的机器上安装它们?

In OS X 10.9, the Downloads pane of Xcode Preferences does not support downloading command-line tools. Use any of the following methods to install command-line tools on your system: If Xcode is installed on your machine, then there is no need to install them. Xcode comes bundled with all your command-line tools. OS X 10.9 includes shims or wrapper executables. These shims, installed in /usr/bin, can map any tool included in /usr/bin to the corresponding one inside Xcode. xcrun is one of such shims, which allows you to find or run any tool inside Xcode from the command line. Use it to invoke any tool within Xcode from the command line. ...