How to detect that a person has been idle on Mac OS X

idle_time.sh

#!/bin/sh

# Output is given in seconds. Taken from http://stackoverflow.com/a/8659356 and *originally* from
# http://hints.macworld.com/article.php?story=20040330161158532 (posted in 2004!!)
echo $((`ioreg -c IOHIDSystem | sed -e '/HIDIdleTime/ !{ d' -e 't' -e '}' -e 's/.* = //g' -e 'q'` / 1000000000))

In my travels I have found 2 other ways to parse the output of ioreg -c IOHIDSystem. The first uses awk to parse the output:

ioreg -c IOHIDSystem | awk '/HIDIdleTime/ {print $NF/1000000000; exit}'

The second uses a combination of grep and awk:

echo $((`ioreg -c IOHIDSystem | grep -m 1 'HIDIdleTime' | awk '{print $NF}'` / 1000000000))

While they are easier to read than the original, the sed still beats the first one on speed and the second one on the number of pipes (and arguably on speed also, but the margin is much closer).