Nagios 3.0 is finally capable of processing multi-line plugin output. The total length of the output must not exceed 8 KB—but you must also make sure that all the transmission paths are compatible for such an amount of data. NRPE currently still needs to be adjusted in the source code (8.5.2 Installation requirements); the plugin
check_by_ssh from the standard plugins inversion 1.4.10 (Chapter 9) can deal with the 8 KB.
The format of the extended and muti-line outputs are described in 8.5.1 Multiple-line plugin output (page 193), and an example of the use of the extended format is provided by the plugin
check_multi (8.5 Summarizing Checks with check_multi from page 191).