Most checks are based on some definite range of threshold values. For example, generate critical alert if the CPU load is more than 80 percent, warning alert if it is between 60 and 80 percent. These values are not restricted to percentages, they can be virtually any numbers depending on our check's logic and requirements.

Most check plugins follow a convention in taking threshold ranges as command-line arguments. This convention may not be followed by all plugins, but most of the standard ones do. This is a recommended way of taking threshold ranges so that it is easy to understand the usage of the plugin by other potential users. The ranges are generally in following format:

[@]start:end

Things to keep in mind about various usages and corresponding interpretations of the following:

Let's look at some examples of ranges:

These threshold values/ranges are usually used for generating warning and critical alerts. The -w command-line switch is used to specify a threshold value/range for the warning alert, and the -c switch is used to specify the threshold value/range for the critical alert. This, again, is a convention, many plugins may not follow.

And some command-line examples are given in the following table:

This is just a convention for using the plugins. Many plugins don't follow it, and it does not apply to plugins that don't need threshold ranges.