How can I find the device uuid's of all connected devices through a command line script?

I am running automated tests on iOS devices. I want to not have to always have all devices connected. So I want to find all device id's and then only start the process of building, deploying, and running tests if that device is connected.

So my question is, how can I find the device uuid's of all connected devices through a shell script?

Thanks!

Edit:

instruments command is now deprecated, you should run instead

xcrun xctrace list devices

Previous answer:

If you have Xcode installed, you can use Instruments to get all known devices also. With

instruments -s devices

The answer from @KKendall set me on the right path. Here's a version with a single sed expression:

system_profiler SPUSBDataType | sed -n -E -e '/(iPhone|iPad)/,/Serial/s/ *Serial Number: *(.+)/\1/p'

install ideviceinstaller on Mac OS X via brew command: brew install ideviceinstaller

then idevice_id -l will work from terminal

I found a similar question about using multiple devices here is my form of the answer that helped me:

 #!/bin/sh
 i=0
 for line in $(system_profiler SPUSBDataType | sed -n -e '/iPad/,/Serial/p' -e '/iPhone/,/Serial/p' | grep "Serial Number:" | awk -F ": " '{print $2}'); do
    UDID=${line}
    echo $UDID
    udid_array[i]=${line}
    i=$(($i+1))
 done

 cnt=${#udid_array[@]}
 for ((i=0;i<cnt;i++)); do
    echo ${udid_array[i]}
 done