implementation of OLS 2005 example in current language

[William Cohen <wcohen at redhat dot com>]

I implemented the OLS 2005 example that tracked opens, reads, and writes 
in the current systemtap language. I did the averages by hand. This 
compiled and ran with a current snapshot of systemtap.

$ stap fileops.stp
4 opens by process "udevd"
75 opens by process "init"
31 opens by process "hald"
16 opens by process "automount"
reads by process "stap": 2 Total bytes= 16384.  Average:8192.
reads by process "init": 155 Total bytes= 140360.  Average:905.
reads by process "sshd": 492 Total bytes= 8060928.  Average:16384.
reads by process "bash": 703 Total bytes= 24576.  Average:34.
writes by process "init": 141 Total bytes= 11972.  Average:84.
writes by process "sshd": 535 Total bytes= 87505.  Average:163.
writes by process "bash": 283 Total bytes= 60052.  Average:212.
writes by process "stap": 1 Total bytes= 4.  Average:4.

-Will
# fileops.stp
# A reimplementation of systemtap example given at OLS 2005
# in the current systemtap language.
#
# 9/6/2005
# Will Cohen

global opens
global reads
global reads_bytes
global writes
global writes_bytes

probe kernel.function("sys_open") {
  opens[pexecname()] += 1;
}

probe kernel.function("sys_read") {
  ++reads[pexecname()];
  reads_bytes[pexecname()] += $count;
}

probe kernel.function("sys_write") {
  ++writes[pexecname()];
  writes_bytes[pexecname()] += $count;
}

probe end {
  foreach (pexecname in opens)
	  log( string(opens[pexecname]) . " opens by process \"" 
		. pexecname ."\"");
  foreach (pexecname in reads)
	  log("reads by process \"" . pexecname . "\": "
		. string(reads[pexecname])
		. " Total bytes= "
		. string(reads_bytes[pexecname]) . ".  Average:"
		. string(reads_bytes[pexecname]/reads[pexecname])
		. ".");
  foreach (pexecname in writes)
	  log("writes by process \"" . pexecname . "\": "
		. string(writes[pexecname])
		. " Total bytes= "
		. string(writes_bytes[pexecname]) . ".  Average:"
		. string(writes_bytes[pexecname]/writes[pexecname])
		. ".");
}