thank you for the help and the explanation!

@Franklin52

your solution worked but I am not sure if it works if the computer has been on for more than 24 hours because then the string changes because the days are being added. So I will have to wait for a couple more hours to test your solution.

For now I am using this command
uptime | sed 's/.*up \(.*\),.*user.*/\1/' | awk '{sub(":", "h ", $0); sub(" ", "", $0);print "uptime: " $0 "min"}'

again I have to wait until my computer has been on for more than 24 hours to see if everything works fine.

But for now thanks a lot for the help. I will be back in a couple of hours to report whether the commands are working or not.

can someone please test the two commands (if your computer has been on for more than 24hours) I just mentioned in this post and post the outcome in the forum? that would be great because I might habe to restart my Computer so I will have to wait another 24 hours to test.

Update: the two above commands do not work! the first one does not work because the string changes as time advances so one cannot use $1, $2, $3.
the second does not work because it always prints min at the end and if I just started up the computer it prints something like that: x secsmin and x minsmin

So right now I am using this command

uptime | sed 's/.*up \(.*\),.*user.*/\1/' | awk '{sub(":", "h ", $0); sub(" mins", "min", $0); sub(" secs", "sec", $0); print "uptime@mac: " $0}'

It works fine until hours and probably days are displayed. How can I insert "min" after the minutes that are displayed? the "h" works fine because I always replace ":" but I do not know how to solve the problem with the min so it will display it properly at any time, no matter how long my computer has been running for.