No, I don't want to install MRTG, RTG, RRDTool, MySQL, Cacti, Observium, PHP, Apache, Nginx, or FastCGI to get one-shot interface statistics.

poll.rb

#!/usr/bin/env ruby

require 'rubygems'
require 'snmp'
require 'time'

def mbps(bytes, duration)
  ((bytes / duration) * 8.to_f) / 1000000
end

def pct(bytes, speed, duration)
  return 0 if speed == 0
  ((100 * (bytes.to_f / duration) * 8.to_f) / speed.to_f).to_i
end

def get_bw(d, i)
  duration = d[i][:ts].to_f - d[i - 1][:ts].to_f
  inbytes = (d[i][:in] - d[i - 1][:in]).abs
  outbytes = (d[i][:out] - d[i - 1][:out]).abs
  speed = d[i][:speed]
  "in: #{'%.2fMbps' % mbps(inbytes, duration)} (#{pct(inbytes, speed, duration)}%),\tout: #{'%.2fMbps' % mbps(outbytes, duration)} (#{pct(outbytes, speed, duration)}%)"
end

unless ARGV.length >= 2
  puts "#{__FILE__} <device> <community> [# of polls, default: 5] [# of seconds to sleep between polls, default: 1]"
  exit 1
end

dev = {
  :host => ARGV[0],
  :community => ARGV[1]
}

enough = false
poll = {}

polls = ARGV[2].to_i
polls = 5 if polls < 2

delay = ARGV[3].to_i || 1
delay = 1 if delay < 1

polls.times do
  SNMP::Manager.open(:Host => dev[:host], :Version => :SNMPv2c, :Community => dev[:community]) do |mgr|
    mgr.walk([ 'ifIndex', 'ifDescr', 'ifSpeed', 'ifHCInOctets', 'ifHCOutOctets' ]) do |row|
      idx, name, speed, inbytes, outbytes = row
      poll[name.value] ||= []
      poll[name.value] << {
        :ts => Time.now,
        :ifindex => idx.value.to_i,
        :interface => name.value.to_s,
        :speed => speed.value.to_i,
        :in => inbytes.value.to_i,
        :out => outbytes.value.to_i
      }
    end
  end

  if enough
    poll.keys.sort.each do |interface|
      data = poll[interface]
      i = data.length - 1
      puts "#{interface.ljust(16)}\t#{data[i][:ts]}\t\t#{get_bw(data, i)}"
    end
    puts
  else
    enough = true
  end

  sleep delay
end