#!/usr/bin/perl -w
#pio: This script provides I/O-related counters for all processes to be used by topio.
#(C) Yong Huang, 2010
#yong321.freeshell.org/freeware/pio.html

chdir "/proc";
opendir PROC, "." or die "Can't open /proc: $!";
while (defined ($file = readdir PROC))
{ if ($file =~ /^\d+$/)		#each file is a pid	
  { open IO, $file."/io" or die "Can't open file /proc/$file/io: $!";
    while (defined ($_=<IO>))
    { last if /^rchar: 0/;	#skip pseudo procs that are kernel threads; their rchar must be 0
      print "$file\t" . qx(cat $file/cmdline) . "\t" if /^rc/;	#print pid when first line of io file
      chomp;
      print substr $_,(index $_,":")+2;
      print (/^c/ ? "\n" : "\t") ;	#line begins with cancelled_write_bytes
    }
    close IO;
  }
}
close PROC;

#As of this writing, /proc/<pid>/io is like
#rchar: 6297
#wchar: 0
#syscr: 15
#syscw: 0
#read_bytes: 0
#write_bytes: 0
#cancelled_write_bytes: 0