Again, a simple benchmark:
Lomanics-iMac:~ lomanic$ time ./load_avg.old ; time ./load_avg
{load1:0.89,load5:0.99,load15:1.01} <nil>
real 0m0.019s
user 0m0.008s
sys 0m0.013s
{load1:0.8876953125,load5:0.98828125,load15:1.0146484375} <nil>
real 0m0.011s
user 0m0.004s
sys 0m0.006s
This is faster and yields more precise results.