I have a macbook pro with OS X 10.8.2. XCode is installed. I know this as it appears in the Applications directory. There are also the xcodebuild and xcode-select files in /
In macOS Catalina, and possibly some earlier versions, you can find out where the command line tools are installed using:
xcode-select -p a.k.a. xcode-select --print-path
Which will, if it is installed, respond with something like:
/Library/Developer/CommandLineTools
To find out which version you have installed there, you can use:
xcode-select -v a.k.a. xcode-select --version
Which will return something like:
xcode-select version 2370.
However, if you attempt to upgrade it to the latest version, assuming it is installed, using this:
xcode-select --install
You will receive in response:
xcode-select: error: command line tools are already installed, use "Software Update" to install updates
Which rather erroneously gives the impression you need to use Spotlight find something called 'Software Update'. In actual fact, you need to continue in the Terminal, and use this:
softwareupdate -i -a a.k.a. softwareupdate --install --all
Which tries to update everything it can and may well respond with:
Software Update Tool
Finding available software
No new software available.
To find out which versions of the different Apple SDKs are installed on your machine, use this:
xcodebuild -showsdks