Unfortunatelye here’s another place where the Mac inspectors are not in parity with the Windows inspectors. It would be idea to use the ‘admin privilege of ’ to determine the users with admin rights, but it only supports Windows and Ubuntu.
Using some older threads I came up with this:
concatenation ", " of strings of values of array "users" of dictionary of file "/private/var/db/dslocal/nodes/Default/groups/admin.plist"
Older threads:
https://www.ibm.com/developerworks/community/forums/html/topic?id=e324ca4d-d537-477d-b7f0-097ea4f546ca