Guns

#!/bin/sh
# -- guns
# 
# Purge inactive memory with rapid i/o
# 
# 26 November 2007
# 'killall $command' is still printing to the terminal
 
# declare variables
before=
after=
memPurged=
pageSize=
pagesPurged=
timeout=15				# in seconds
command="du /"			
 
showUsage="Usage: $(basename $0) [-h] [-t seconds] [-c \"command\"]"
 
function printError() 
{
	echo >&2 $showUsage
	echo >&2 
	echo >&2 "See '$(basename $0) -h' for more details."
}
 
function printHelp() 
{
	echo "Purge inactive memory with rapid i/o."
	echo 
	echo $showUsage
	echo 
	echo "Supported Options"
	echo "-----------------"
	echo "-t{seconds}\tSet the amount of time for the command to run.
Default"
	echo "\t\tis 5 seconds."
	echo "-c{\"command\"}\tSet the command to run. Default is 'du /'"
	echo "-h\t\tDisplay this help and exit"
}
 
function getMemFree()
{
	# the "$3-0" bit is a dirty way to chop the period at the end
	vm_stat | awk '/Pages free/ {intMemFree=$3-0; print intMemFree}'
}
 
function getPageSize()
{
	vm_stat | awk '/page size/ {print $8}'
}
 
# variables in: $timeout and $command 
function purgeMem()
{
	# print a message
	printf "Accessing disk"
 
	$command >/dev/null 2>&1 &
 
	# give some feedback
	for (( i = 0; i < $timeout*2; i++ )); do	# Display a dot every half
		sleep .5								# second, so multiply $timeout
		printf .								# by two
	done
 
	# kill the process; if exited early, this will be a zombie process
	killall $command >/dev/null 2>&1 &
 
	if [[ $? == 0 ]]; then
		echo "stop"
	else
		echo "runaway process!"
		exit 20
	fi	
}
 
# 
# Main
# 
 
while getopts ":ht:c:" option; do
	case $option in
		h ) printHelp; exit;;
		t ) timeout=$OPTARG;;
		c ) command=$OPTARG;;
		\?) echo >&2 "Invalid option!\n"; printError; exit 3
	esac
done
shift $(($OPTIND-1))
 
before=$(getMemFree)
 
purgeMem 
 
# set variables
after=$(getMemFree)
let pagesPurged=$after-$before
pageSize=$(getPageSize)
 
# calculate and print
let memPurged=($pagesPurged * $pageSize / 2**20)
printf "%d MB purged.\n" $memPurged