UNIX for Dummies Questions & Answers

I'm trying to get the uptime of my computer (Mac OS X) and I can go into the terminal and type "uptime" OK, and that gives me a string with the uptime in it. The problem is that the string changes a lot, and its very difficult to get the data I'm trying to extract out cleanly.

Now I have 3 options to get the time:
a) Use a lot of complicated, very messy and pretty damn in-efficient code to get the data, and have occasional errors in the display.
b) Find the kernel that is accessed to get the uptime before its parsed and outputted in the terminal, and get it manually myself.
c) Find out how long a process that was opened at boot time (eg. init) has been running, and that will be my boot time.

The second two options are the ones i'm trying to use, but I don't know how to do either of those things.

Can someone here give me a little help how to do these things?

I don't use OS X, but the kernel variable is called boottime in most kernels. It is an integer as would be returned by the time() system call. Your process will need read permission on /dev/mem to read it. If you have adb you can use that to read it via a shell script.

I use "ps -fp 1" rather than "uptime" to see when a system booted.

Option 4 would be to find a file that is changed at boottime. Do your startup scripts keep a log? What was the last time that log changed? If no such file exists, add something to the startup scripts to record boottime.

Thanks for that, I'll look into those options when I get back from school.