Life in the prison camps is all about survival of the fittest at its most brutal. It's the law of the jungle in One Day in the Life of Ivan Denisovich, and for the people in the camps, competition for resources is ruthless. Prisoners have to compete for everything here – food, warmth, decent work assignments, rewards, etc. They even compete for cigarette butts.
In order to survive and to maintain a competitive edge against others, a zek has to be constantly alert. Shukhov is especially aware of this need. If he could have a motivational poster by his bunk, it would probably feature Mad-Eye Moody yelling "Constant Vigilance!" Since the stakes of competition in the camp are literally life and death, no relationship is sacred and prisoners often screw over their "friends" in an effort to keep themselves alive. Unlike Blanche DuBois, of Tennessee Williams's A Streetcar Named Desire, prisoners can't rely on the "kindness of strangers" here. Prisoners must rely only on themselves in order to maintain a necessary competitive edge.
Though competition is important, not all prisoners actually do it. Some survive in different ways, such as receiving help from friends.
All prisoners compete against one another constantly. Even acts of charity are forms of competition since they involve favors and manipulation.