How to check uptime of Linux/Unix/macOS system/server using console command?

In order to check since the last login (or boot time) of the system how many days and time have elapsed one may make use of the uptime or the w command. In this tutorial, we will stick to the uptime command.

Syntax: uptime

This is a BSD General Command and so works on Linux/Unix/macOS or Bash for Windows. This command was added to the BSD list in the year 1994 in BSD version 3.0

Let's see an example of this command.

$ uptime
0:30  up 18 days, 14:58, 2 users, load averages: 1.07 1.29 1.31

How to read the output of the uptime command?

As you can see in the above example there are multiple sections to the output you see of the command. Let's break them down

• 0:30 -> This is the time in HH:mm when the command was fired. The time on the system/server.
• up 18 days, 14:58 -> This show for how many days the system is up and running followed the hours and minutes.
• 2 users -> Next it shows number of users that are logged in to the system.
• load averages: 1.07 1.29 1.31 -> As the name suggests it is the load averages - you see three numbers here that represents 3 load averages in the last one, five and fifteen minutes respectively.

The best way to get more details about any shell command is by using the manual,

$ man uptime

UPTIME(1) BSD General Commands Manual UPTIME(1)

NAME
 uptime -- show how long system has been running

SYNOPSIS
 uptime

DESCRIPTION
  The uptime utility displays the current time, 
  the length of time the system has been up, 
  the number of users, and the load average of the system 
  over the last 1, 5, and 15 minutes.

SEE ALSO
  w(1)

HISTORY
 The uptime command appeared in 3.0BSD.

BSD                             April 18, 1994                             BSD
(END)

✏️ The above examples are based on macOS running Big Sur.

What are the optional parameters available with uptime command?

If you are using Linux OS - you would see that there are multiple options that you can make use of with the uptime command:

1. -p, --pretty => This option will display the uptime in pretty format.
2. -s, --since => This option will display system up since details.
3. -V, --version => This option will display version information and exit.

Aslo you can make use of -h to display the help details,

$ uptime -h

Usage:
uptime [options]

Options:
 -p, --pretty   show uptime in pretty format
 -h, --help     display this help and exit
 -s, --since    system up since
 -V, --version  output version information and exit

For more details see uptime(1).

Let's see some examples: 1. Show uptime in pretty format

$ uptime -p
up 11 weeks, 22 days, 21 hours, 10 minute

2. system up since

$ uptime -s
2021-07-16 12:12:55

3. Output version information and exit

$ uptime -V
uptime from max-ag 2.1.11

Note if you try to use the command with options macOS you will get errors as below,

bash-3.2$ uptime -p
uptime: illegal option -- p
usage: uptime
bash-3.2$ uptime -s
uptime: illegal option -- s
usage: uptime
bash-3.2$ uptime -V
uptime: illegal option -- V
usage: uptime

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