awk: getting data based on previous lines

Here's a little awk script that I wrote to collect data from a field where it's heading is in the line above (both are at $4 - space separated). The input file looks like this:

ARTMGA01_usage_07Mar07-1500:# CPU SUMMARY
ARTMGA01_usage_07Mar07-1500-# USER SYS IDLE WAIT INTR SYSC CS RUNQ AVG5 AVG30 AVG60 FORK VFORK
ARTMGA01_usage_07Mar07-1500- 4 6 90 0 1002 7214 9093 0 0.21 0.18 0.17 2.73 0.59
ARTMGA01_usage_07Mar07-1500:# CPU SUMMARY
ARTMGA01_usage_07Mar07-1500-# USER SYS IDLE WAIT INTR SYSC CS RUNQ AVG5 AVG30 AVG60 FORK VFORK
ARTMGA01_usage_07Mar07-1500- 4 9 87 0 905 7552 8530 1 0.32 0.21 0.18 2.20 0.40
ARTMGA01_usage_07Mar07-2100:# CPU SUMMARY
ARTMGA01_usage_07Mar07-2100-# USER SYS IDLE WAIT INTR SYSC CS RUNQ AVG5 AVG30 AVG60 FORK VFORK
ARTMGA01_usage_07Mar07-2100- 4 5 90 0 1052 7777 9492 0 0.19 0.18 0.18 2.65 0.59

Here's the actual code:

BEGIN {}
{
if ($4 ~ /IDLE/) {
getline
idleval = idleval + $4
count++
}
}
END {
print "Total: " idleval
print "Count: " count
print "Average: " idleval / count
}

There's nothing new in this code that we haven't already covered but it's a good 'simple' example of how awk's getline function can be used. We essentially do a search for 'IDLE' then skip to the next line with getline and collect the value at $4 (field four). The 'count' value is incremented for every line that matches 'IDLE' which is how we can then work out the average:

print "Average: " idleval / count

('idleval' divided by 'count').