>  What happens or is it possible that they could change their exit code? What about if there is no status number with their exit as in just plain exit? Does that still pass?

@chrisopedia in any UNIX based system every command returns an exit code (from `0`-`255`). `0` means true/successful completion, while `!= 0` means false/something went wrong.

For more in-depth information, please read: http://tldp.org/LDP/abs/html/exit-status.html.

> `xcode select -p` will print out an exit code that is not equal to 0?

@chrisopedia `xcode-select -p &> /dev/null; printf $?` will print out the exit code for `xcode-select -p` no matter what value it is. Then, `-ne 0 ` will check if that exit code is different then `0`, and if it is, then XCode will need to be installed.