Validate available disk space before installing package

Background

While testing a Self Service policy to install Adobe Creative Cloud Master Collection 2015, I was greeted by a Finder dialog box informing me I was nearly out of disk space.

The following script leverages JSS Parameter 4 and verifies there is enough available disk space before continuing with the policy. If there is not enough free disk space, a message is displayed to the end-user and Self Service is forcibly quit. (Is there a way to just simply stop the policy and leave Self Service running?)

Script

#!/bin/sh
####################################################################################################
#
# ABOUT
#
#   Check Free Space: Leverages JSS Parameter 4 to verify there is enough available disk space before continuing with the policy. If there is not enough free disk space, a message is displayed to the end-user and Self Service is forcibly quit.
#
####################################################################################################
#
# HISTORY
#
#   Version 1.0, 17-Jun-2015, Dan K. Snelson
#
####################################################################################################
# Import logging functions
source /path/to/logging/script/goes/here/logging.sh
####################################################################################################

# Variables
requiredSpace="$4"            # Available Space Required (in GBs)
availableSpace=`/usr/sbin/diskutil info / | grep "Volume Free Space:" | awk '{print $4}'`
availableSpaceInt=$(/bin/echo "($availableSpace+0.5)/1" | bc)
totalSpace=`/usr/sbin/diskutil info / | grep "Total Size:" | awk '{print $3}'`
/bin/echo "`now` *** Check Free Space ***" >> $logFile
/bin/echo "`now` Required Space: $requiredSpace" >> $logFile
/bin/echo "`now` Available Space: $availableSpaceInt" >> $logFile

if [ "$availableSpaceInt" -lt "$requiredSpace" ]; then
    /usr/sbin/jamf displayMessage -message "Insufficient Free Space Available

This installation requires $requiredSpace GB.
There is $availableSpace GB available.

"
    /usr/bin/killall "Self Service"
    exit 1      ## Failure
else
    /bin/echo "`now` There is enough free space available" >> $logFile
fi


exit 0      ## Success