interface-statistics

#!/usr/bin/env ruby

#
# Simple script that parses the interface usage statistics
# as returned by 'ip -s link'
#
# This script should be useful for machine statistic collection
# ie: ethernet bytes transmitted and received, etc.
#

# helper assert function
def assert(should_be_true, message)
    if !should_be_true
        STDERR.puts message
        exit(false)
    end
end

#
# Parse command options
#

require 'optparse'
options = {}

opt_parser = OptionParser.new do |opts|
	opts.banner = "Usage: interface-statistics [options]"
	
	opts.separator ""
	
	options[:format] = :text
	opts.on("-f", "--format TYPE", [:text, :hash],
		"Specify output format:", 
		"text: simple text output", 
		"hash: ruby hash output (useful for use in later ruby scripts)") do |format|
	
		options[:format] = format
	end
	
end

opt_parser.parse!(ARGV)

# get input to parse
#
# try reading from stdin
# otherwise invoke ip -s link directly

if STDIN.tty?
    # no pip-ed input...invoke directly
    cmd = "ip -s link"
    input = `#{cmd}`
    
    assert($?.exitstatus == 0, "Command failed.")
else
    input = ARGF.read    
end

# split results into lines
lines = input.split("\n")

# sanity check number of lines
assert(lines.length != 0        , "Command output empty")
assert(lines.length % 6 == 0    , "Command output not expected length")

# group lines into block of 6...each interface's results are on 6 lines 
interfaces_lines = lines.each_slice(6).to_a

interfaces_hash = {}

# iterate over each interface's set of lines
interfaces_lines.each do |interface_lines|
    interface_name = interface_lines[0].split()[1].chomp(":")

    # sanity check and get RX
    expected_RX_line = "    RX: bytes  packets  errors  dropped overrun mcast   "
    assert(interface_lines[2] == expected_RX_line, "RX line not expected: #{expected_RX_line}")
    rx_bytes = interface_lines[3].split()[0].to_i
       
    # sanity check and get TX
    expected_TX_line = "    TX: bytes  packets  errors  dropped carrier collsns "
    assert(interface_lines[4] == expected_TX_line, "TX line not expected: #{expected_TX_line}")
    tx_bytes = interface_lines[5].split()[0].to_i
    
    interfaces_hash[interface_name] = { :rx_bytes => rx_bytes, :tx_bytes => tx_bytes };
end

# format output
if options[:format] == :text
	# print plain text ouput
	puts "interface rx_bytes tx_bytes"

	interfaces_hash.each_pair do |name, values|
		puts "#{name} #{values[:rx_bytes]} #{values[:tx_bytes]}"
	end
else
	# print ruby hash string
	puts interfaces_hash
end