Simple answer: They die, immediately. If the suit is breeched and the body exposed to the vacuum of space, the body fluids immediately boil, blood, lymph, intercellular fluid, everything, causing masive damage and death. At best, one has a few seconds, but during that time, every limb would be paralyzed by the physical swelling.
Radiation, temperature and other effects are all secondary and by the time they are noticeable, the astronaut would be long gone.
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