I had XCode Commandline Tools installed for sure, but not XCode itself.
None of the available answers to get the version worked.
pkgutil didn't give me the package of the XCode Commandline Tools, with none of the suggested package names.
Not having XCode installed (and having no need for it), I could not look in settings dialogs of that either.
xcode-select --version only gave me the version of
xcode-select itself, with no clue as to the commandline tools version.
softwareupdate --list told me everything was up to date.
However I knew that my version must be out of date as the installer for one of homebrew packages told me so!
How I finally found out what version of the XCode Commandline Tools is installed I stumbled upon the command:
Which listed 12.3 as the last version it updated...
Display Name Version Date
------------ ------- ----
Safari 14.0 04/11/2020, 12:26:12
Command Line Tools for Xcode 12.1 04/11/2020, 22:38:33
Safari 14.0.2 15/12/2020, 16:38:27
Safari 14.0.1 15/12/2020, 16:38:27
Command Line Tools for Xcode 12.3 15/12/2020, 16:38:27
macOS Big Sur 11.2.1 14/02/2021, 20:57:56
macOS Big Sur 11.2.2 11.2.2 08/03/2021, 09:02:20
So when you know for sure the commandline tools are installed (because, for instance,
xcode-select --install tells you so) but none of the other methods works, check