getting return result from executing

Hi, I need to execute another program from within my program and capture the result.  For example:

executing "bin/date +%H" will return "14" if it is 2 o clock
i need to capture the "14" into a variable int hr

i tried this:

int hr=execve("/bin/date","+%H",envp);

but all that does is run the date program, output the "14" and then it does not return a value.

I know that execve does not return a value unless it fails.

What command can I use to execute another command and get the output of it?

Sorry so long.
Thanks,
Josh