To monitor a log file that is constantly updating, we can use the tail command with the -f option. The tail command is used to display the last few lines of a file, and the -f option allows it to follow the file and display new lines as they are added to the file.  For example, to monitor the log file "log.txt" and display new lines as they are added to the file, we can use the following command:  tail -f log.txt  This will display the last few lines of the log file, and then continue to display new lines as they are added to the file. The tail command will keep running until we stop it, so we can use it to effectively monitor the log file in real-time.  We can also use the -n option to specify the number of lines to display, or the -s option to specify the interval between updates.  For example, to display the last 100 lines of the log file and update the display every 5 seconds, we can use the following command:  tail -n 100 -s 5 log.txt  Overall, the tail command is a useful tool for monitoring log files and other files that are constantly updating. It allows us to view new lines as they are added to the file, making it easier to track changes and identify issues.