Which program runs a command in specific intervals and refreshes the display of the program's output?

The program that runs a command at specific intervals and refreshes the display of its output is 'watch'. This command is particularly useful for monitoring changes in the output of a program over time, allowing users to see updated information in real-time without having to manually execute the command repeatedly. By using 'watch', you can specify an interval for execution, and it automatically clears the terminal screen and re-runs the command, making it an effective tool for observing dynamic data, like system status or resource usage.

Other choices, such as 'repeat', typically don't provide the functionality for continuous monitoring and refreshing of output in real-time. 'cron', on the other hand, is designed for scheduling tasks at specified times or intervals but does not refresh output in a terminal window like 'watch'. Lastly, 'exec' is a command that replaces the current shell process with a given command, rather than executing a command repeatedly at intervals. Thus, 'watch' is the best fit for the requirement described in the question.