Intro

Ruleset: The Root Element

The root element of an XML configuration file is the procwatch element. It has one implicit attribute, the version attribute, set to "1.0".

The procwatch element symbolizes our ruleset, and the childs of the root are our rules.

Rules: The Childs of the Root

The direct descendants of the root element procwatch, are the watch elements, which can occur 1 time or more often.

The watch element has one required attribute, the name attribute, which gives the watch (or job, rule) a descriptive name like "httpd-count".

Each watch element symbolizes a single rule, containing a regular expression to search for, one or more conditions to evaluate and one or more actions to be taken.

A Rule

A rule consists of three child elements:

• pattern

• condition

• execute

Rule Element: pattern

The pattern element describes the perl compatible regular expression which should be evaluated against a column of the output of ps.

There is one required attribute, the match attribute, defining the column name of the output of ps in lowercase like "command" or "vsz".

This makes System::ProcWatch highliy versatile and should make it usable with any platforms procps program.

The pattern elements content solely consits of the perl compatible regular expression to match against the column defined in the match attribute. The PCRE MUST contain the start and end delimiter and MAY contain any PCRE modifiers.

Example: <pattern match="command">/sbin\/httpd/</pattern>

Rule Element: condition

The condition element defines conditions that MUST evaluate to TRUE at all so that later defined actions will be executed.

The condition element has one required and one optional attribute, the required one being type, which MUST be one of "presence" or "attr", and the optional one being attr. However, if the type attribute equals to "attr" the attr attribute MUST be present.

The attr attribute represents a column of procps' output like "user" or "%mem".

Conditions

Dependent on the content of the type attribute, syntax and behavior of the condition element differ.

A condition with type "presence" MAY be empty, thus always evaluating to true.

Child Elements of condition may be:

• min

  Found value MUST exceed defined value.

• max

  Found value MUST NOT exceed defined value.

• is

  Found value MUST be equal to defined value.

• isnot

  Found value MUST NOT be equal to defined value.

• sum

  The sum of found values MUST NOT exceed defined sum.

You may combine them to define for instance a range from min to max.

Rule Element: execute

The execute element defines actions that should be taken if the condition applies.

It has one required attribute, the type attribute, which MUST equal to one of "shell" or "php".

Obviously the content of the execute element is executed either on the shell through shell_exec() or directly in PHP through eval().

The execute element MAY occur any times.

There are some special variables that will automagically be available in execute statements:

• $msg

  This contains a general message, what has happened. It is quoted in single quotes for save usage and is available in shell and php executes.

• $pids

  This contains all PIDs of the processes that have been found. They are enclosed by single quotes and parenthesis.

  Example: '(433, 444, 455, 466)'

• $procs

  This is a somewhat serialized php array in string format containing all information gained from ps and looks like: array(array('pid' => 344, 'command' => '/usr/sbin/httpd' ...))

  It is only available in php executes and can easily be used in function callbacks:

  <execute type="php">get_procs($procs);</execute>