Determining the installed version of Mac OS XEdit

Created 3/24/2007, updated 10/14/2017

Using sw_vers

$ sw_vers
ProductName:    Mac OS X
ProductVersion: 10.4.9
BuildVersion:   8P135

Using uname

$ uname -a
Darwin example.local 8.9.0 Darwin Kernel Version 8.9.0: Thu Feb 22 20:54:07 PST 2007; root:xnu-792.17.14~1/RELEASE_PPC Power Macintosh powerpc

Looking on the filesystem

cat /System/Library/CoreServices/SystemVersion.plist

Or if the above file is in binary format and you have the Xcode tools installed you can open it in the Property List Editor:

open /System/Library/CoreServices/SystemVersion.plist