Find Mac OSX version installed using AppleScript

You can get the OS version as a display string using:

set _versionString to system version of (system info)

If you want to compare this to another version, be sure to use considering numeric strings:

considering numeric strings
    set _newEnough to _versionString ≥ "10.9"
end considering

Otherwise, you can run into problems such as "10.4.11" being less than "10.4.9", or "10.10" being less than "10.9".

You can also use system attribute. This lets you get the version number as an integer so that you don't need to worry about comparing dot-separated strings:

set _versionInteger to system attribute "sysv" -- 4240 == 0x1090 (Mac OS X 10.9)
set _isMavericksOrBetter to (system attribute "sysv") ≥ 4240 -- 0x1090
set _isMountainLionOrBetter to (system attribute "sysv") ≥ 4224 -- 0x1080
set _isLionOrBetter to (system attribute "sysv") ≥ 4208 -- 0x1070

You can also use system attribute to get the individual version components without having to parse a string:

set _major to system attribute "sys1" -- 10
set _minor to system attribute "sys2" -- 9
set _bugFix to system attribute "sys3" -- 0

Here is how to get OSX version in AppleScript, using built-in functions:

set sysinfo to system info
set osver to system version of sysinfo

On OS X Mavericks the result is "10.9".

One-liner: set osver to system version of (system info)

I'm not on a Mac, so there may be a better way to do this, but the first approach that comes to mind is just executing a shell command to query the OS version.

http://developer.apple.com/technotes/tn2002/tn2065.html#TNTAG2

http://developer.apple.com/DOCUMENTATION/Darwin/Reference/ManPages/man1/sw_vers.1.html

Based on these references, you probably want to do something like:

set os_version to do shell script "sw_vers -productVersion"