#!/usr/bin/env ruby
require 'optparse'

@compare = "free"

opts = OptionParser.new do |o|
  o.banner = "Usage: check_mem [options]"

  o.on( "-w", "--warning WARNING", "Warning on less than n MB free" ) do |w|
    @warning = w.to_i
  end

  o.on( "-c", "--critical CRITICAL", "Critical on less than n MB free" ) do |c|
    @critical = c.to_i
  end

  o.on( "-p", "--plus", "Use free + buffers + cache for comparison" ) do |p|
    @compare = "maybe_free"
  end

  o.on("-h", "--help", "This help" ) do
    puts o
    exit
  end
end

begin
	opts.parse!( ARGV )

	free_data=`free`.split("\n")[1].split

	total=free_data[1].to_i
	used=free_data[2].to_i

	shared=free_data[3].to_i
	buffers=free_data[4].to_i
	cached=free_data[5].to_i

	free=total - used
	maybe_free=free + buffers + cached

	if eval("#{@compare} < @critical")
		puts "CRITICAL Mem #{free} M free, #{maybe_free} M free (+buffers and cache)"
		exit 2
	elsif eval("#{@compare} < @warning")
		puts "CRITICAL Mem #{free} M free, #{maybe_free} M free (+buffers and cache)"
		exit 1
	else
		puts "OK Mem #{free} M free, #{maybe_free} M free (+buffers and cache)"
		exit 0
	end
rescue => exc
	STDERR.puts "E: #{exc.message}"
	STDERR.puts opts.to_s
	exit 3
end