reference.txt

* Nagios plug-in development guidelines
http://nagiosplug.sourceforge.net/developer-guidelines.html

* exit code

Nagios 每次在查询一个服务的状态时，产生一个子进程，并且它使用来自该命令
的输出和退出代码来确定具体的状态。退出状态代码的含义如下所示：

OK —退出代码 0—表示服务正常地工作。
WARNING —退出代码 1—表示服务处于警告状态。
CRITICAL —退出代码 2—表示服务处于危险状态。
UNKNOWN —退出代码 3—表示服务处于未知状态。

最后一种状态通常表示该插件无法确定服务的状态。例如，可能出现了内部错误。

Use: exit <code>
0 = OK
1 = Warning
2 = Critical
3 = Unknown

* performance data
Performance data is defined by Nagios as "everything after the | of
the plugin output".

format:

'label'=value[UOM];[warn];[crit];[min];[max]

- space separated list of label/value pairs
- label can contain any characters
- the single quotes for the label are optional. Required if spaces, =
  or ' are in the label
- label length is arbitrary, but ideally the first 19 characters are
  unique (due to a limitation in RRD). Be aware of a limitation in the
  amount of data that NRPE returns to Nagios
- to specify a quote character, use two single quotes
- warn, crit, min or max may be null (for example, if the threshold is
  not defined or min and max do not apply). Trailing unfilled
  semicolons can be dropped
- min and max are not required if UOM=%
- value, min and max in class [-0-9.]. Must all be the same UOM
- warn and crit are in the range format (see Section 2.5). Must be the
  same UOM
- UOM (unit of measurement) is one of:
  - no unit specified - assume a number (int or float) of things (eg,
    users, processes, load averages)
  - s - seconds (also us, ms)
  - % - percentage
  - B - bytes (also KB, MB, TB)
  - c - a continous counter (such as bytes transmitted on an interface)