bootstat/bootstat_get_last

#!/bin/sh
# Copyright 2012 The ChromiumOS Authors
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

# Converts a floating point number of seconds to a properly rounded
# number of integer milliseconds.
seconds_to_ms() {
  # Millisecond metrics are always reported as integers values.
  #
  # By default awk will print large numbers in exponential format which
  # conflicts with shell arithmetic used in some scripts.
  #
  # awk is using 32-bit integers which is not enough for the millisecond
  # calculation.
  #
  # This way we use a floating point format with 0 fractional numbers here.
  echo "$1" | awk -v OFMT="%.0f" '{ print int($1 * 1000.0 + 0.5)}'
}

EVENT="$1"
shift
if [ $# -eq 0 ]; then
  set -- time
fi

while [ $# -gt 0 ]; do
  case "$1" in
    time)
      TAG=uptime
      FIELD=1
    ;;
    # Emit time in milliseconds instead of fractional seconds.
    time-ms)
      TAG=uptime
      FIELD=1
      EMIT_MS=1
    ;;
    read-sectors)
      TAG=disk
      FIELD=3
    ;;
    write-sectors)
      TAG=disk
      FIELD=7
    ;;
    *)
      shift
      continue
    ;;
  esac

  if [ "$2" = "before" ] ; then
    BEFORE="$3"
    shift 2
  fi

  # The 'boot-complete' upstart job tests for whether an event has
  # been recorded by calling this script, so it's not an error if
  # the requested event doesn't exist.
  EVENTFILE="/run/bootstat/${TAG}-${EVENT}"
  if [ -f "${EVENTFILE}" ]; then
    # For "time" measurement the result will have a value measured in seconds.
    # Therefore we need a fractional part to report sub-second intervals. On
    # the other hand, for "read-sectors" and "write-sectors" we always expect
    # integer values. This is why we use "general" format for the result here.
    #
    # On the other hand, AWK will print large numbers in exponential format,
    # which is not suitable for the shell arithmetic.
    #
    # TODO: fix this discrepancy.
    result="$(awk -v field="${FIELD}" -v before="${BEFORE}"            \
      '(!before || $field < before) {result=$field} END{print result}' \
      "${EVENTFILE}"
    )"
    if [ -n "${EMIT_MS}" ]; then
      result="$(seconds_to_ms "${result}")"
    fi
    echo "${result}"
  fi

  BEFORE=""
  shift
done