A "howto check OS-X Version in a commandline" post with less then 100 words :P Open Terminal.app Enter: "sw_vers" and hint Enter The output should look like this:
Welcome to Darwin!
fidel@MacPro~: sw_vers
ProductName: Mac OS X
ProductVersion: 10.5.5
BuildVersion: 9F33
fidel@MacPro~:
Thats is :D
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