If you want to know how long a command took to execute, you can use the Bash built-in command time. Simply prepend your command with time and once it finishes, it will tell you the duration.

The output will be something like this

real - is the full time it took to run the command (how long you waited).
user - is the CPU time used by the program itself.
sys - is the CPU time used by the system calls

GNU time

There is also a gnu time command which gives a little bit more information. It also allows non-Bash users to time their commands.

You can typically run the GNU time command as follows