You may have to configure Nmap with the command. Also, on some newer Mac OS X versions, the libpcap version of the library provided by Apple may be too old. Note that on some older versions of Mac OS X, you may have to replace the command. Once you have installed Xcode and the command-line tools, follow the compilation instructions found in the section called “Linux/Unix Compilation and Installation from Source Code”. You can install them by opening Xcode from the Applications folder, opening Preferencechoosing the Download header icon and clicking the Install button next to “ Command Line Tools”.
Xcode installations don't always include the command line tools. Xcode is not installed by default, but can be downloaded free of Apple's developer tools that include GCC and the rest of the usual build
