Finding Out the Operating System Version

Example 14-1 finds out which OS the computer is running by using a property of the Finder called, aptly enough, product version. The script first saves product version, a string, to a variable called myOS. You need to enclose this variable assignment in a tell block that targets the Finder, because product version is a property of the Finder. Otherwise, AppleScript would not know which product version you were referring to. The script then tests the OS version to determine if it is less than 8.5 with the following code statement:

characters 1 thru 3 of myOS

This returns a list like {"9”, “.”,"0"}. This list is converted to text with the as text coercion statement, so now it looks like “9.0.” The entire statement is:

(characters 1 thru 3 of myOS as text)

This string (“9.0”) is then coerced or converted to a real number (9.0), which is a number with a decimal point and fractional part (unlike an integer, which is a whole number), so we can compare this number with 8.5. This coercion is not strictly necessary, but I like to make explicit conversions so I always know which data type I am working with.

If the myOS value (e.g., 9.0) is less than 8.5, a dialog displays telling the user the script will quit. This function derives from a script that I wrote depended on Mac OS 8.5 or greater to run properly.

Example 14-1. OS Version Retriever

getOS(  )
(* function definition *)
on getOS(  )
   tell application "Finder"
      set myOS to (product version)
      if ((characters 1 thru 3 of myOS as text) as real) < 8.5 then
         display dialog "You cannot run this applet unless the computer" &¬
         " has Mac OS 8.5. or later." & return & return &¬
         giving up after 45
         return -- quit applet
      else
         display dialog "Good, your OS is: " & myOS
      end if
   end tell
end getOS