#!/usr/bin/env bash

# This program is part of Percona Toolkit: http://www.percona.com/software/
# See "COPYRIGHT, LICENSE, AND WARRANTY" at the end of this file for legal
# notices and disclaimers.

# ########################################################################
# A bunch of snippets of awk code, to be reused in the functions below.
# ########################################################################
awk_parse_line="
      # The entries in each stat line are as follows:
      #   1	major
      #   2	minor
      #   3	device name
      dev = \$3;
      #   4	reads
      reads = \$4;
      #   5	reads merged
      reads_merged = \$5;
      #   6	read sectors
      read_sectors = \$6;
      #   7	ms spent reading
      ms_spent_reading = \$7;
      #   8	writes
      writes = \$8;
      #   9	writes merged
      writes_merged = \$9;
      #  10	written sectors
      written_sectors = \$10;
      #  11	ms spent writing
      ms_spent_writing = \$11;
      #  12	IOs in progress
      ios_in_progress = \$12;
      #  13	ms spent doing io
      ms_spent_doing_io = \$13;
      #  14	ms spent, weighted by ios_in_progress
      ms_weighted = \$14;
"

# NOTE: this one is necessary in order to get the device listing.  NOTE: the
# 'devs' variable is initialized to 0, but it is pre-incremented, so a) it will
# reflect the accurate number of devices found (after filtering); b) iteration
# must be from 1 to devs, not from 0 to devs-1.
awk_save_sample_to_first="
      # Keep track of the natural order of the devices, so we can print them out
      # nicely later; and also keep the first-ever line of output.  This only
      # executes the first time through.
      devices[dev]++;
      if ( devices[dev] == 1 ) {
         devsort[++devs] = dev;
         first[dev \"_reads\"]             = reads;
         first[dev \"_reads_merged\"]      = reads_merged;
         first[dev \"_read_sectors\"]      = read_sectors;
         first[dev \"_ms_spent_reading\"]  = ms_spent_reading;
         first[dev \"_writes\"]            = writes;
         first[dev \"_writes_merged\"]     = writes_merged;
         first[dev \"_written_sectors\"]   = written_sectors;
         first[dev \"_ms_spent_writing\"]  = ms_spent_writing;
         first[dev \"_ios_in_progress\"]   = ios_in_progress;
         first[dev \"_ms_spent_doing_io\"] = ms_spent_doing_io;
         first[dev \"_ms_weighted\"]       = ms_weighted;
      }
"

awk_set_iterations_and_timestamp="
      iterations++;
      curr_ts = \$2;
      if ( iterations == 1 ) {
         first[\"ts\"] = curr_ts;
      }
"

awk_save_sample_to_curr="
      curr[dev \"_reads\"]             = reads;
      curr[dev \"_reads_merged\"]      = reads_merged;
      curr[dev \"_read_sectors\"]      = read_sectors;
      curr[dev \"_ms_spent_reading\"]  = ms_spent_reading;
      curr[dev \"_writes\"]            = writes;
      curr[dev \"_writes_merged\"]     = writes_merged;
      curr[dev \"_written_sectors\"]   = written_sectors;
      curr[dev \"_ms_spent_writing\"]  = ms_spent_writing;
      curr[dev \"_ios_in_progress\"]   = ios_in_progress;
      curr[dev \"_ms_spent_doing_io\"] = ms_spent_doing_io;
      curr[dev \"_ms_weighted\"]       = ms_weighted;
"

awk_save_curr_as_prev="
      curr[\"ts\"] = curr_ts;
      for (i in curr) {
         prev[i] = curr[i];
      }
      for ( i = 1; i <= devs; i++ ) {
         dev = devsort[i];
         prev[dev \"_sum_ios_in_progress\"] += curr[dev \"_ios_in_progress\"];
      }
      ts = curr_ts;
"

awk_find_max_device_name_length="
      mdev = 6;
      for ( i = 1; i <= devs; i++ ) {
         dlen = length(devsort[i]);
         if ( dlen > mdev ) {
            mdev = dlen;
         }
      }
"

awk_get_overall_increments="
         # Get incremental numbers.
         reads             = curr[dev \"_reads\"]             - first[dev \"_reads\"];
         reads_merged      = curr[dev \"_reads_merged\"]      - first[dev \"_reads_merged\"];
         read_sectors      = curr[dev \"_read_sectors\"]      - first[dev \"_read_sectors\"];
         ms_spent_reading  = curr[dev \"_ms_spent_reading\"]  - first[dev \"_ms_spent_reading\"];
         writes            = curr[dev \"_writes\"]            - first[dev \"_writes\"];
         writes_merged     = curr[dev \"_writes_merged\"]     - first[dev \"_writes_merged\"];
         written_sectors   = curr[dev \"_written_sectors\"]   - first[dev \"_written_sectors\"];
         ms_spent_writing  = curr[dev \"_ms_spent_writing\"]  - first[dev \"_ms_spent_writing\"];
         ms_spent_doing_io = curr[dev \"_ms_spent_doing_io\"] - first[dev \"_ms_spent_doing_io\"];
         ms_weighted       = curr[dev \"_ms_weighted\"]       - first[dev \"_ms_weighted\"];
         in_progress       = curr[dev \"_ios_in_progress\"];
         tot_in_progress   = prev[dev \"_sum_ios_in_progress\"];
"

awk_compute_incremental_stats="
         # Get incremental numbers.
         reads             = curr[dev \"_reads\"]             - prev[dev \"_reads\"];
         reads_merged      = curr[dev \"_reads_merged\"]      - prev[dev \"_reads_merged\"];
         read_sectors      = curr[dev \"_read_sectors\"]      - prev[dev \"_read_sectors\"];
         ms_spent_reading  = curr[dev \"_ms_spent_reading\"]  - prev[dev \"_ms_spent_reading\"];
         writes            = curr[dev \"_writes\"]            - prev[dev \"_writes\"];
         writes_merged     = curr[dev \"_writes_merged\"]     - prev[dev \"_writes_merged\"];
         written_sectors   = curr[dev \"_written_sectors\"]   - prev[dev \"_written_sectors\"];
         ms_spent_writing  = curr[dev \"_ms_spent_writing\"]  - prev[dev \"_ms_spent_writing\"];
         ms_spent_doing_io = curr[dev \"_ms_spent_doing_io\"] - prev[dev \"_ms_spent_doing_io\"];
         ms_weighted       = curr[dev \"_ms_weighted\"]       - prev[dev \"_ms_weighted\"];
         in_progress       = curr[dev \"_ios_in_progress\"];
         tot_in_progress   = curr[dev \"_sum_ios_in_progress\"];
"

awk_reset_accumulators="
         t_reads             = 0;
         t_reads_merged      = 0;
         t_read_sectors      = 0;
         t_ms_spent_reading  = 0;
         t_writes            = 0;
         t_writes_merged     = 0;
         t_written_sectors   = 0;
         t_ms_spent_writing  = 0;
         t_ms_spent_doing_io = 0;
         t_ms_weighted       = 0;
         t_in_progress       = 0;
"

awk_copy_variables_to_accumulators="
         t_reads             = reads;
         t_reads_merged      = reads_merged;
         t_read_sectors      = read_sectors;
         t_ms_spent_reading  = ms_spent_reading;
         t_writes            = writes;
         t_writes_merged     = writes_merged;
         t_written_sectors   = written_sectors;
         t_ms_spent_writing  = ms_spent_writing;
         t_ms_spent_doing_io = ms_spent_doing_io;
         t_ms_weighted       = ms_weighted;
"

awk_compute_read_write_stats="
         # Compute the per-second stats for reads, writes, and overall.
         reads_sec        = t_reads / elapsed;
         read_requests    = t_reads_merged + t_reads;
         mbytes_read_sec  = t_read_sectors / elapsed / 2048;
         read_conc        = t_ms_spent_reading / elapsed / 1000 / devs_in_group;
         if ( t_reads > 0 ) {
            read_rtime    = t_ms_spent_reading / t_reads;
            avg_read_sz   = t_read_sectors / t_reads;
         }
         else {
            read_rtime    = 0;
            avg_read_sz   = 0;
         }
         if ( read_requests > 0 ) {
            read_merge_pct = 100 * t_reads_merged / read_requests;
         }
         else {
            read_merge_pct = 0;
         }
         writes_sec          = t_writes / elapsed;
         write_requests      = t_writes_merged + t_writes;
         mbytes_written_sec  = t_written_sectors / elapsed / 2048;
         write_conc          = t_ms_spent_writing / elapsed / 1000 / devs_in_group;
         if ( t_writes > 0 ) {
            write_rtime      = t_ms_spent_writing / t_writes;
            avg_write_sz     = t_written_sectors / t_writes;
         }
         else {
            write_rtime      = 0;
            avg_write_sz     = 0;
         }
         if ( write_requests > 0 ) {
            write_merge_pct = 100 * t_writes_merged / write_requests;
         }
         else {
            write_merge_pct = 0;
         }
         # Compute the numbers for reads and writes together, the things for
         # which we do not have separate statistics.
         # Busy is what iostat calls %util.  This is the percent of
         # wall-clock time during which the device has I/O happening.
         busy = 100 * t_ms_spent_doing_io / (1000 * elapsed * devs_in_group);
         if ( first[\"ts\"] > 0 ) {
            line_ts = sprintf(\"%5.1f\", curr_ts - first[\"ts\"]);
         }
         else {
            line_ts = sprintf(\"%5.1f\", 0);
         }
"

# Returns true if the column should be displayed.
col_ok() {
   result=$(echo $1 | awk "/${OPT_c:-.}/{print 0}")
   return ${result:-1}
}

# Based on which columns match $OPT_c, designs a header and line printf format,
# and a printf statement to print the lines.
design_print_formats() {
   # For each device, print out the following: The timestamp offset and
   # device name.  Must embed the mdev Awk variable here, because the device
   # name is variable-length.
   fmt="\"%5s %-\" mdev \"s";
   hdr="${fmt}";
   vars="";
   # The per-second reads, read size (kB), per-second MB read, read merged pct, read
   # concurrency, and average response time for each read.
   if col_ok rd_s    ; then fmt="${fmt} %7.1f";   hdr="${hdr}    rd_s";  vars="${vars}, reads_sec"; fi
   if col_ok rd_avkb ; then fmt="${fmt} %7.1f";   hdr="${hdr} rd_avkb";  vars="${vars}, avg_read_sz"; fi
   if col_ok rd_mb_s ; then fmt="${fmt} %7.1f";   hdr="${hdr} rd_mb_s";  vars="${vars}, mbytes_read_sec"; fi
   if col_ok rd_mrg  ; then fmt="${fmt} %5.0f%%"; hdr="${hdr} rd_mrg";   vars="${vars}, read_merge_pct"; fi
   if col_ok rd_cnc  ; then fmt="${fmt} %6.1f";   hdr="${hdr} rd_cnc";   vars="${vars}, read_conc"; fi
   if col_ok rd_rt   ; then fmt="${fmt} %7.1f";   hdr="${hdr}   rd_rt";  vars="${vars}, read_rtime"; fi
   # The same for writes.
   if col_ok wr_s    ; then fmt="${fmt} %7.1f";   hdr="${hdr}    wr_s";  vars="${vars}, writes_sec"; fi
   if col_ok wr_avkb ; then fmt="${fmt} %7.1f";   hdr="${hdr} wr_avkb";  vars="${vars}, avg_write_sz"; fi
   if col_ok wr_mb_s ; then fmt="${fmt} %7.1f";   hdr="${hdr} wr_mb_s";  vars="${vars}, mbytes_written_sec"; fi
   if col_ok wr_mrg  ; then fmt="${fmt} %5.0f%%"; hdr="${hdr} wr_mrg";   vars="${vars}, write_merge_pct"; fi
   if col_ok wr_cnc  ; then fmt="${fmt} %6.1f";   hdr="${hdr} wr_cnc";   vars="${vars}, write_conc"; fi
   if col_ok wr_rt   ; then fmt="${fmt} %7.1f";   hdr="${hdr}   wr_rt";  vars="${vars}, write_rtime"; fi
   # Then busy%, in-progress, and line-ending.
   if col_ok busy    ; then fmt="${fmt} %3.0f%%"; hdr="${hdr} busy";     vars="${vars}, busy"; fi
   if col_ok in_prg  ; then fmt="${fmt} %6d";     hdr="${hdr} in_prg";   vars="${vars}, t_in_progress"; fi
   fmt="${fmt}\n\"";
   hdr="${hdr}\n\"";
   awk_print_header="printf(${hdr}, \"#ts\", \"device\");";
   awk_print_line="printf(${fmt}, line_ts, dev${vars});";
}

# Prints out one line for each disk, summing over the interval from first to
# last sample.
group_by_disk () {
   [ -z "${awk_print_line}" ] && design_print_formats
   cat > /tmp/aspersa.awk <<EOF
   BEGIN {
      devs    = 0;
      devname = "${OPT_d}";
   }
   \$1 !~ /TS/ && \$3 ~ devname {
      ${awk_parse_line}
      ${awk_save_sample_to_first}
      ${awk_save_sample_to_curr}
   }
   \$1 ~ /TS/ && NR > 1 {
      ${awk_set_iterations_and_timestamp}
   }
   END {
      if ( iterations < 2 ) {
         exit;
      }
      ${awk_find_max_device_name_length}
      ${awk_print_header}
      elapsed = curr_ts - first["ts"];
      for ( i = 1; i <= devs; i++ ) {
         dev               = devsort[i];
         ${awk_get_overall_increments}
         ${awk_copy_variables_to_accumulators}
         # The in-progress operations needs to be averaged.
         t_in_progress     = (tot_in_progress / (iterations - 1));
         devs_in_group     = 1;
         ${awk_compute_read_write_stats}
         line_ts="{" (iterations - 1) "}";
         ${awk_print_line}
      }
   }
EOF
   awk -f /tmp/aspersa.awk "$@"
}

# Prints out one line for each sample, summing up all disks together.
group_by_sample() {
   [ -z "${awk_print_line}" ] && design_print_formats
   cat > /tmp/aspersa.awk <<EOF
   BEGIN {
      devs    = 0;
      devname = "${OPT_d}";
   }
   \$1 !~ /TS/ && \$3 ~ devname {
      ${awk_parse_line}
      ${awk_save_sample_to_first}
      ${awk_save_sample_to_curr}
   }
   \$1 ~ /TS/ && NR > 1 {
      ${awk_set_iterations_and_timestamp}
      printed_a_line = 0;
      if ( iterations == 1 ) {
         # The second time we see a timestamp we are ready to print a header.
         mdev    = 6;
         if ( devs == 1 ) {
            ${awk_find_max_device_name_length}
         }
         ${awk_print_header}
      }
      elapsed = curr_ts - ts;
      if ( ts > 0 && elapsed > ${OPT_i:-0} ) {
         # Reset the t_ variables to zero.
         ${awk_reset_accumulators}
         for ( i = 1; i <= devs; i++ ) {
            dev               = devsort[i];
            # Save the incrementals into named variables.
            ${awk_compute_incremental_stats}
            # Add the increments to the accumulators.
            t_reads             += reads;
            t_reads_merged      += reads_merged;
            t_read_sectors      += read_sectors;
            t_ms_spent_reading  += ms_spent_reading;
            t_writes            += writes;
            t_writes_merged     += writes_merged;
            t_written_sectors   += written_sectors;
            t_ms_spent_writing  += ms_spent_writing;
            t_ms_spent_doing_io += ms_spent_doing_io;
            t_ms_weighted       += ms_weighted;
            t_in_progress       += in_progress;
         }
         devs_in_group = devs;
         ${awk_compute_read_write_stats}
         if ( devs > 1 ) {
            dev     = "{" devs "}";
         }
         else {
            dev     = devsort[1];
         }
         ${awk_print_line}
         printed_a_line = 1;
      }
      if ( iterations == 1 || printed_a_line == 1 ) {
         # We don't save "curr" as "prev" on every sample we see, because if the
         # interval of printing is more than one sample, we want "prev" to be
         # the first sample in the interval, not the previous sample seen.
         ${awk_save_curr_as_prev}
      }
   }
EOF
   awk -f /tmp/aspersa.awk "$@"
}

# Prints out one line for each sample, for each disk that matches the pattern.
# TODO: omits the first sample.
group_by_all () {
   [ -z "${awk_print_line}" ] && design_print_formats
   cat > /tmp/aspersa.awk <<EOF
   BEGIN {
      devs    = 0;
      devname = "${OPT_d}";
   }
   \$1 !~ /TS/ && \$3 ~ devname {
      ${awk_parse_line}
      ${awk_save_sample_to_first}
      ${awk_save_sample_to_curr}
   }
   \$1 ~ /TS/ && NR > 1 {
      ${awk_set_iterations_and_timestamp}
      ${awk_find_max_device_name_length}
      if ( iterations > 1 ) {
         if ( devs > 1 || iterations == 2 ) {
            ${awk_print_header}
         }
         ${awk_reset_accumulators}
         elapsed = curr_ts - prev["ts"];
         for ( i = 1; i <= devs; i++ ) {
            dev               = devsort[i];
            ${awk_compute_incremental_stats}
            ${awk_copy_variables_to_accumulators}
            t_in_progress     = curr[dev "_ios_in_progress"];
            devs_in_group     = 1;
            ${awk_compute_read_write_stats}
            ${awk_print_line}
         }
      }
      ${awk_save_curr_as_prev}
   }
EOF
   awk -f /tmp/aspersa.awk "$@"
}

# Show current help and settings
print_help() {
   cat <<-HELP
   You can control this program by key presses:
   ------------------- Key ------------------- ---- Current Setting ----
   A, D, S) Set the group-by mode              ${OPT_g:-(none)}
   c) Enter an awk regex to match column names ${OPT_c:-(none)}
   d) Enter an awk regex to match disk names   ${OPT_d:-(none)}
   i) Set the sample size in seconds           ${OPT_i:-(none)}
   s) Set the redisplay interval in seconds    ${OPT_s:-(none)}
   p) Pause the program
   q) Quit the program
   ------------------- Press any key to continue -----------------------
	HELP
}

usage() {
   if [ "${OPT_ERR}" ]; then
      echo "${OPT_ERR}"
   fi
   cat <<-USAGE
Usage: $0 [OPTIONS] [FILE]
   $0 does two things: 1) get /proc/diskstats periodically 2) aggregate the result.
   If you specify a FILE, or send input to STDIN, then step 1) is not performed.
Options:
   -c COLS     Awk regex of which columns to include (default cnc|rt|mb|busy|prg).
   -d DEVICES  Awk regex of which devices to include.
   -g GROUPBY  Group-by mode (default disk); specify one of the following:
      disk)    # Each line of output shows one disk device.
      sample)  # Each line of output shows one sample of statistics.
      all)     # Each line of output shows one sample and one disk device.
   -i INTERVAL In -g sample mode, include INTERVAL seconds per sample.
   -k KEEPFILE File to save diskstats samples in (default /tmp/aspersa).
               If a non-default filename is used, it will be saved for later
               analysis.
   -n SAMPLES  When in interactive mode, stop after N samples.
   -s INTERVAL Sample /proc/diskstats every N seconds (default 1).
	USAGE
   exit 1
}

# The main code that runs by default.  Arguments are the command-line options.
main() {

   # Get command-line options.
   for o; do
      case "${o}" in
         --)
            shift; break;
            ;;
         --help)
            usage;
            ;;
         -c)
            shift; OPT_c="${1}"; shift;
            ;;
         -d)
            shift; OPT_d="${1}"; shift;
            ;;
         -g)
            shift; OPT_g="${1}"; shift;
            case "${OPT_g}" in
               disk)
                  ;;
               sample)
                  ;;
               all)
                  ;;
               *)
                  OPT_ERR="Bad option value";
                  usage
                  ;;
            esac
            ;;
         -i)
            shift; OPT_i="${1}"; shift;
            ;;
         -k)
            shift; OPT_k="${1}"; shift;
            ;;
         -n)
            shift; OPT_n="${1}"; shift;
            ;;
         -s)
            shift; OPT_s="${1}"; shift;
            ;;
         -*)
            OPT_ERR="Unknown option ${o}."
            usage
            ;;
      esac
   done
   OPT_i="${OPT_i:-}"; export OPT_i;
   OPT_k="${OPT_k:-/tmp/aspersa}"; export OPT_k;
   OPT_n="${OPT_n:-}"; export OPT_n;
   OPT_c="${OPT_c:-cnc|rt|mb|busy|prg}"; export OPT_c;
   OPT_d="${OPT_d:-}"; export OPT_d;
   OPT_s="${OPT_s:-1}"; export OPT_s;
   OPT_g="${OPT_g:-disk}"; export OPT_g;

   # We need to "do the right thing."  The user might invoke any of several
   # ways; we get samples every now and then unless there is data on STDIN or a
   # file to read.
   if [ $# -gt 0 -o -p 1 ]; then
      READ_FILE=1
   fi

   # If we are interactive and there's no file, we gather stats to play with.
   if [ -z "${READ_FILE}" ]; then
      PARENT=$$
      loops=1
      while true; do
         cat /proc/diskstats >> "${OPT_k}"
         date +"TS %s.%N %F %T" >> "${OPT_k}"
         if ! ps -p ${PARENT} >/dev/null 2>&1 ; then
            # The parent process doesn't exist anymore -- quit.
            finished="yes"
         elif [ "${OPT_n}" ]; then
            if [ "${loops}" -gt "${OPT_n}" ] ; then
               finished="yes"
            fi
         fi
         if [ "${finished}" ]; then
            if [ "${OPT_k}" = "/tmp/aspersa" ]; then
               rm -f /tmp/aspersa
            fi
            break;
         fi
         sleep ${OPT_s}
         loops=$(($loops + 1))
      done &

      # Sleep until the loop has gathered 2 samples.
      while [ "$(grep -c TS "${OPT_k}")" -lt "2" ]; do
         sleep .5
      done
   fi

   if [ -z "${READ_FILE}" ]; then
      group_by_${OPT_g} "${OPT_k}"
   else
      group_by_${OPT_g} "$@"
   fi

   # Don't be "interactive" unless the user actually has control.
   if [ ! -t 0 -o ! -t 1 ]; then
      exit;
   fi

   # We use this in iterative-loop mode
   if [ -z "${READ_FILE}" ]; then
      TAIL_LINES=$(cat /proc/diskstats | wc -l)
   fi

   while [ -z "${OPT_n}" -o "${i:-0}" -le "${OPT_n:-0}" ]; do
      i=$(( ${i:-1} + 1 ))

      # Re-decide the timeout every loop
      if [ -z "${READ_FILE}" ]; then
         TIMEOUT="-t ${OPT_s}"
      fi
      cmd="" # Must reset, some bash won't clear it after a read times out.
      read $TIMEOUT -n 1 -s cmd junk
      case "${cmd}" in
         A)
            OPT_g="all"
            FIRST_LOOP="1"
            ;;
         d)
            read -p "Enter a disk/device pattern: " OPT_d
            FIRST_LOOP="1"
            ;;
         D)
            OPT_g="disk"
            FIRST_LOOP="1"
            ;;
         c)
            read -p "Enter a column pattern: " OPT_c
            FIRST_LOOP="1"
            awk_print_line="" # Make it re-compute the column headers
            ;;
         i)
            read -p "Enter a sample size: " OPT_i
            FIRST_LOOP="1"
            ;;
         p)
            read -n 1 -p "Paused - press any key to continue"
            ;;
         q)
            break
            ;;
         s)
            read -p "Enter a redisplay interval: " OPT_s
            FIRST_LOOP="1"
            ;;
         S)
            OPT_g="sample"
            FIRST_LOOP="1"
            ;;
         '?')
            print_help; read -n1 -s
            ;;
      esac

      if [ -z "${READ_FILE}" ]; then
         if [ -z "${FIRST_LOOP}" ]; then
            # We only print out what's new since last printout
            N=$(($TAIL_LINES * 2 + 2)) # Extra is for TS lines
            tail -n $N "${OPT_k}" 2>/dev/null | group_by_${OPT_g} | tail -n +2
         else
            group_by_${OPT_g} "${OPT_k}"
         fi
         FIRST_LOOP=""
      else
         group_by_${OPT_g} "$@"
      fi

   done

   if [ "${OPT_k}" = "/tmp/aspersa" ]; then
      rm -f "/tmp/aspersa"
   fi
   rm -f /tmp/aspersa.awk
}

# Execute the program if it was not included from another file.  This makes it
# possible to include without executing, and thus test.
if [ "$(basename "$0")" = "pt-diskstats" ] || [ "$(basename "$0")" = "bash" -a "$_" = "$0" ]; then
    main "$@"
fi

# ############################################################################
# Documentation
# ############################################################################
:<<'DOCUMENTATION'
=pod

=head1 NAME

pt-diskstats - Read a file generated from /proc/diskstats and summarize it.

=head1 SYNOPSIS

Usage: pt-diskstats [OPTION...]

=head1 DESCRIPTION

The file read should look like this:

   <contents of /proc/diskstats>
   TS <timestamp>
   <contents of /proc/diskstats>
   ... et cetera
   TS <timestamp>  <-- must end with a TS line.

=head1 AUTHORS

Baron Schwartz

=head1 COPYRIGHT, LICENSE, AND WARRANTY

This program is copyright 2010-2011 Baron Schwartz, 2011 Percona Inc.
Feedback and improvements are welcome.

THIS PROGRAM IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.

This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation, version 2; OR the Perl Artistic License.  On UNIX and similar
systems, you can issue `man perlgpl' or `man perlartistic' to read these
licenses.

You should have received a copy of the GNU General Public License along with
this program; if not, write to the Free Software Foundation, Inc., 59 Temple
Place, Suite 330, Boston, MA  02111-1307  USA.
legal.pod (END) 

=cut

DOCUMENTATION