if you are trying to keep up with changes that are being made in real time to a file, cat is not the best choice. A good example of files that can change often and rapidly are log files. For example, you may need to start a program and look at that program's log file to see what it is doing. For this case, use the tail -f file command. tail -f file - Follow the file. Displays data as it is being written to the file.
