Using uptime

uptime is another simple and useful command that can be used to verify how long your Unix system has been up and running. The uptime command returns the current time, the number of users logged in to the system, how long the system has been running, and the amount of load that the system is under. Just type uptime at the command prompt, as follows:

>uptime
6:30am up 12:50, 3 users, load average: 0.15, 0.11, 0.04

In this example, we can see that uptime returns the current time, up since, how many users are currently logged in to Unix, and the load average. Just about everything here should be self-explanatory except for the load average. The load average is composed of three values: the first value is the load on the system during the past minute, the second value is the load average during the last 10 minutes, and the third value is the load average during the last 15 minutes. These values are rarely more than one or two. If you see a system load average of anything more than five, your computer is busy, and you may see performance degradation.